Alexey Guzey’s Theses on Sleep gained a lot of popularity and acclaim on LessWrong and among people I follow on social media, despite largely consisting of what I think were weak arguments and misleading claims. I found that a bit surprising, so I decided to write a post pointing out several of the mistakes I think he’s made, and reporting some of what the academic literature on sleep seems to show.
One of Guzey’s theses is that “depression triggers/amplifies oversleeping while oversleeping triggers/amplifies depression.” The first piece of evidence he uses to support that is people on /r/BipolarReddit saying that they sleep a lot when depressed, and sleep very little when manic. However, there’s a big problem with using that as evidence.
The DSM-5 specifies subtypes of depression that have opposing relationships with sleep. Depression with melancholic features is associated with early morning awakening, whereas depression with atypical features is associated with hypersomnia.
Guzey’s evidence is misleading because people with bipolar disorder are disproportionally prone to having atypical features during their depressive episodes. So, unsurprisingly, his evidence from bipolar disorder patients is not representative of what you see in the general population: both long and short sleep duration are associated with depression (and, relevantly, suicide as well, in adults as well as adolescents).
I’m surprised no one in the comments of this post brought up this objection – it only takes a very quick Google Scholar search to see that the relationship between sleep duration and depression is not linear.
Guzey hypothesizes that
Sleep deprivation appears to increase BDNF [and therefore neurogenesis?]
He then proceeds to link to a few papers that showed up when he Googled “sleep deprivation bdnf”. These sources agree that acute sleep deprivation increases BDNF expression, but some also say that the opposite may happen when sleep deprivation is chronic, which Guzey fails to mention in his post.
From The Brain-Derived Neurotrophic Factor: Missing Link Between Sleep Deprivation, Insomnia, and Depression:
Chronic sleep deprivation and insomnia can act as an external stressors and result in depression, characterized by hippocampal BDNF downregulation along with disrupted frontal cortical BDNF expression, as well as reduced levels and impaired diurnal alterations in serum BDNF expression.
Guzey also links to The link between sleep, stress and BDNF, which seems to be only an abstract. After a bit of searching, I found this full-text paper with some of the same authors, which appears to have an almost identical abstract (?). It concludes with the following:
[O]ur findings are in line with the hypothesis of an increased stress vulnerability due to sleep loss which may lead to a decrease in BDNF. [...] While we report a reduction of BDNF levels linked to sleep disturbance reflecting chronic stress on the one side, we and others consistently showed that prolonged wakefulness caused by SD (partial or total), which can be considered as an acute stressor for the brain, leads to a rapid increase of BDNF (1,36).
I feel grumpy, dumb and distractable every time I sleep less than 7 or so hours. I can’t do things that require focused attention like solving physics homework problems very effectively, and I don’t get nearly as much pleasure when I attempt doing so. My memory becomes very poor: after a recent night of <6 hours of sleep, I somehow forgot the reasoning behind several Manifold Markets trades I had made the prior evening and just stared at them in utter confusion for several minutes before remembering.
I have the impression that most people have a similar experience. Guzey has a cute explanation of how this is consistent with his thesis that sleep deprivation doesn’t make you grumpy or dumb, but the fact that I and others I know have this experience with sleep deprivation obviously makes it so that I have a high prior that it’s harmful to cognition and mood. It sounds a lot more plausible that sleep deprivation being harmful in those ways is causing both my personal experience with it to be terrible and academic research to find that it’s harmful, instead of a different factor explaining each thing. Guzey has to add quite a few epicycles to his theory to explain the evidence.
To the extent that you and the people you know feel the same way I do after a night of sleep deprivation, your prior should be high as well.
Guzey claims that “most sleep research is extremely unreliable and we shouldn’t conclude much on the basis of it,” but there are problems with that. Firstly because he doesn’t seem to believe that about sleep research that favors his hypotheses. Guzey, after all, uses sleep research to show that Matthew Walker’s book is terrible and fraudulent. So it seems that he wants to trust sleep research when it says that sleep deprivation is not as bad as Walker shows, but doesn’t want to trust it when it says that sleep deprivation is not harmless.
Secondly, he bases that assertion on a claim that sleep science is “mostly just rebranded cognitive psychology” (and that it is only not facing a severe replication crisis because sleep experiments are expensive), which is very misleading. Unlike the famously unreliable cognitive science results, the finding that sleep deprivation is harmful for cognition (1) in fact gets replicated a lot (see the section below on meta-analyses of sleep restriction studies, as well as this meta-analysis of total sleep deprivation studies) and (2) is consistent with a lot of people’s experiences (for examples, see this addendum.) So it’s hard to see how Guzey’s criticisms apply.
Guzey says, in his post:
I wrote large chunks of this essay having slept less than 1.5 hours over a period of 38 hours. I came up with and developed the biggest arguments of it when I slept an average of 5 hours 39 minutes per day over the preceding 14 days. At this point, I’m pretty sure that the entire “not sleeping ‘enough’ makes you stupid” is a 100% psyop. It makes you somewhat more sleepy, yes. More stupid, no. I literally did an experiment in which I tried to find changes in my cognitive ability after sleeping 4 hours a day for 12-14 days, I couldn’t find any. My friends who I was talking to a lot during the experiment simply didn’t notice anything.
I don’t think that “feeling smart after sleep deprivation” (or any of those other things) is nearly enough evidence to make you conclude that “ ‘not sleeping ‘enough’ makes you stupid’ is a 100% psyop” if you start out with even a halfway reasonable prior, and especially if you appropriately update on what the sleep literature says.
I looked for meta-analyses that investigated the effect of experimental or quasi-experimental nighttime sleep restriction on cognition. I found three, and am quoting the relevant conclusions from them:
The neurocognitive consequences of sleep restriction: A meta-analytic review:
The current meta-analytic review revealed that restricted sleep results in significant neurocognitive deficits (g = −0.383) in a sample of 1688 participants derived from 71 different study populations. This effect was apparent across multiple cognitive domains, with the largest effects being observed on measures of sustained attention (g = −0.409) and EF (g = −0.324), and within these domains, attentional lapses and (g = −0.516) and behavioural inhibition (g = −0.464) specifically.
Meta-regression analyses indicated that age-adjusted sleep deficit (β=-.206, p=.033), cumulative days of restricted sleep (days; β=-.015, p=.019), subjective sleepiness (β=-.040, p=.016), biological sex (β=.0318, p=.009), and sleep latency (β=.012, p=.013) accounted for a significant proportion of the variance in the observed effect of sleep restriction on overall cognitive abilities.
Sleep Loss and Performance in Residents and Nonphysicians: A Meta-Analytic Examination:
Chronic partial sleep loss also resulted in a significant reduction in cognitive performance, with a correct d value of -.886.
A Meta-Analysis of the Effect of Experimental Sleep Restriction on Youth’s Attention and Hyperactivity (on people under 18 years old only):
A total of 13 samples (N = 268) examined the difference in youth’s attention performance between baseline (control) sleep and restricted sleep. The overall effect size of −0.19 was significant (95% CI: −0.34−0.03; p = .02); Q(13) = 21.98, p = .04, I 2 = 45.40% (see Figure 2). The I^2 index of 45.40% indicates a small to moderate amount of heterogeneity in effect sizes across studies (Card, 2012). However, the trim and fill method for addressing publication bias (Duval & Tweedie, 2000a; Duval & Tweedie, 2000b) revealed asymmetry in the funnel plots for the difference in attention outcomes between sleep restricted and baseline sleep. One study to the left of the mean was unmatched. The counterpart of this study was imputed to the right of the mean, resulting in a non-significant and small adjusted effect size of −0.14 (95% CI: −0.32–.04).Six samples (N = 279) examined the difference in attention between extended sleep (sleep extension) and sleep restriction. The overall effect size of −0.37 was significant (95% CI: −0.55 to −0.19, p < .0001) and represents a small to medium effect size (Lipsey & Wilson, 2001), though this effect was heterogeneous between studies Q(5) = 15.29, p = .009, I 2 = 67.30% (see Figure 2). The I 2 index of 67.30% indicates a moderate to large amount of heterogeneity in effect sizes across studies (Card, 2012). Based on trim-and-fill analyses, asymmetry was also present for attention outcomes between restricted and extended sleep, with two studies to the left of the mean unmatched, resulting in a significant adjusted effect size of −0.26 (95% CI: −0.46 to −0.05), which is considered a small to medium effect (Lipsey & Wilson, 2001).
A total of 13 samples (N = 268) examined the difference in youth’s attention performance between baseline (control) sleep and restricted sleep. The overall effect size of −0.19 was significant (95% CI: −0.34−0.03; p = .02); Q(13) = 21.98, p = .04, I 2 = 45.40% (see Figure 2). The I^2 index of 45.40% indicates a small to moderate amount of heterogeneity in effect sizes across studies (Card, 2012). However, the trim and fill method for addressing publication bias (Duval & Tweedie, 2000a; Duval & Tweedie, 2000b) revealed asymmetry in the funnel plots for the difference in attention outcomes between sleep restricted and baseline sleep. One study to the left of the mean was unmatched. The counterpart of this study was imputed to the right of the mean, resulting in a non-significant and small adjusted effect size of −0.14 (95% CI: −0.32–.04).
Six samples (N = 279) examined the difference in attention between extended sleep (sleep extension) and sleep restriction. The overall effect size of −0.37 was significant (95% CI: −0.55 to −0.19, p < .0001) and represents a small to medium effect size (Lipsey & Wilson, 2001), though this effect was heterogeneous between studies Q(5) = 15.29, p = .009, I 2 = 67.30% (see Figure 2). The I 2 index of 67.30% indicates a moderate to large amount of heterogeneity in effect sizes across studies (Card, 2012). Based on trim-and-fill analyses, asymmetry was also present for attention outcomes between restricted and extended sleep, with two studies to the left of the mean unmatched, resulting in a significant adjusted effect size of −0.26 (95% CI: −0.46 to −0.05), which is considered a small to medium effect (Lipsey & Wilson, 2001).
The average age-adjusted sleep deficit in the first meta-analysis was 3.83 hours (SD = 1.25). (This is in comparison with the median recommended amount of sleep for each age group (so 8 hours per night for non-elderly adults), not the average amount of sleep people in each age group actually get.) I couldn’t find information about the other ones, but I have a high credence that they examined studies with a roughly similar protocol; I’ve combed through a lot of individual sleep restriction studies before and they rarely seem to involve making people sleep for < 3.5 hours.
I also found a meta-analysis investigating the effects of napping, and it finds that it’s beneficial, which is probably relevant:
Effects of a Short Daytime Nap on the Cognitive Performance: A Systematic Review and Meta-Analysis:
Overall cognitive performance did not differ at baseline (t0) between groups (effect size −0.03, 95% CI −0.14 to 0.07), and improved in the nap group following the nap (t1) (0.18, 0.09 to 0.27), especially for alertness (0.29, 0.10 to 0.48). Sensitivity analyses gave similar results comparing only randomized controlled trials, and after exclusion of outliers.
There’s also (weaker) evidence that, contrary to what Guzey hypothesizes, there is no cognitive adaptation to chronic sleep restriction. From this article:
Contrary to a popular belief that healthy adults can acclimate to sleep loss, the effects of chronic partial sleep loss appear to be cumulative.9-11 Specifically, sleepiness has been found to increase9 and performance on tests of vigilance and mathematical calculations to decline across 7 days of 5 and even 7 hours of sleep per night.10,11 Subjects often underestimate their own degree of sleep-related impairments in vigilance after 1 week of partial sleep restriction.9,12 Thus, they may mistakenly believe that they have acclimated to sleep deprivation.In addition to reduced vigilance, verbal processing and complex problem solving13,15 are impaired with both short-term and chronic partial sleep loss.
Contrary to a popular belief that healthy adults can acclimate to sleep loss, the effects of chronic partial sleep loss appear to be cumulative.9-11 Specifically, sleepiness has been found to increase9 and performance on tests of vigilance and mathematical calculations to decline across 7 days of 5 and even 7 hours of sleep per night.10,11 Subjects often underestimate their own degree of sleep-related impairments in vigilance after 1 week of partial sleep restriction.9,12 Thus, they may mistakenly believe that they have acclimated to sleep deprivation.
In addition to reduced vigilance, verbal processing and complex problem solving13,15 are impaired with both short-term and chronic partial sleep loss.
See also footnote 2 () on the matter of cognitive adaptation.
I do recognize that even meta-analyses of experimental studies can obviously be very problematic, and so this section is not conclusive evidence that moderate sleep restriction impairs cognition (and not only because conclusive evidence is not a thing). But it’s not as if Guzey has any better evidence to argue that “ ‘not sleeping ‘enough’ makes you stupid’ is a 100% psyop.”
One of Guzey’s theses is that “[o]ccasional acute sleep deprivation is good for health and promotes more efficient sleep.” His argument supporting that thesis is pretty much that, because some types of acute stress (such as exercising and fasting) are good, and acute sleep deprivation causes acute stress, then acute sleep deprivation is also good. (Yes, that does seem to actually be the entirety of his argument in that section. You can read it yourself.)
The obvious problem with that argument is that the set of things that cause acute bodily stress is much larger than the set of things that cause long-term benefits. Stubbing your toe, for example, causes acute bodily stress. Guzey’s argument works equally well for showing that occasional toe-stubbing is good for health as for showing that occasional acute sleep deprivation is.
In this section, Guzey lists lines of evidence that bring him to the conclusion that “decreasing sleep by 1-2 hours a night in the long-term has no negative health effects.” The lines of evidence are:
A sleep researcher who trains sailors to sleep efficiently in order to maximize their race performance believes that 4.5-5.5 hours of sleep is fine.70% of 84 hunter-gatherers studied in 2013 slept less than 7 hours per day, with 46% sleeping less than 6 hours.A single-point mutation can decrease the amount of required sleep by 2 hours, with no negative side-effects.A brain surgery can decrease the amount of sleep required by 3 hours, with no negative-side effects.Sleep is not required for memory consolidation.
Apart from (2), we don’t have any indication of the long-term outcomes of the groups of people he mentioned. So I don’t know how these points could be more than weak and circumstantial evidence of this section’s thesis.
(For that matter, barely any of those even rigorously measure the health effects of short sleep at all. In a sense, they confirm that these people are not immediately dying or getting very acutely sick or something, and I guess I can interpret Guzey as merely wanting to claim that, but it’s not exactly a novel or surprising claim.)
(Also, the 5th line of evidence doesn’t even seem to be related to health.)
I searched Embase for meta-analyses on the effect of experimental sleep restriction on a host of health-related variables, and this is what I found.
Effects of sleep manipulation on markers of insulin sensitivity: A systematic review and meta-analysis of randomized controlled trials:
Whole-body insulin sensitivity was also reduced after short sleep when measured by the hyperinsulinemic euglycemic clamp, but peripheral insulin sensitivity was not affected. In addition, circadian misalignment and slow wave sleep suppression negatively affected insulin sensitivity, while rapid eye movement sleep disturbance and sleep fragmentation had no effect.
Effects of sleep restriction on metabolism-related parameters in healthy adults: A comprehensive review and meta-analysis of randomized controlled trials:
Participants consumed 252.8 more kcal/d (p = 0.011) under sleep restriction than under normal sleep. Partial sleep restriction resulted in a 0.34 kg weight gain (p = 0.003). Sleep restriction also decreased insulin sensitivity (standardized mean difference = −0.70, p < 0.01). Significant changes in brain activity in response to food stimuli were observed under sleep restriction, particularly regions related to cognitive control and reward.
Sleep Restriction Effects on BP: Systematic Review & Meta-analysis of RCTs:
Overall, sleep restriction did not result in significant changes in systolic blood pressure (SBP) or diastolic blood pressure (DBP) and heart rate (HR). The respective weighted mean difference (MD) was 1.0 mmHg (95%CI, -2.3-4.2; p = 0.57), -0.4 mmHg (95%CI, -3.2-2.4; p = 0.80), and 2.0 bpm (95%CI, -2.2-6.2; p = 0.34).
Sleep Disturbance, Sleep Duration, and Inflammation: A Systematic Review and Meta-Analysis of Cohort Studies and Experimental Sleep Deprivation:
Experimental sleep deprivation, either for partial or total night, was not associated with CRP [...], IL-6 [...], or TNFα [...]. Likewise, sleep restriction over several days was not associated with CRP [...], IL-6 [...], or TNFα [...].
(Eyeballing each of those meta-analyses’ lists of studies, it seems that, in most of them, time in bed was restricted to 4-5 hours, with the range being from ~3.5 to ~5.5.)
So experimental sleep restriction (presumably during short periods of time) seems to impair things like insulin sensitivity and the regulation of satiety, but not blood pressure or inflammatory markers.
Importantly, the metabolic effects of sleep restriction found in the first two meta-analyses seem consistent with the finding that short sleep duration is associated with weight gain in observational studies (particularly in younger persons), which perhaps indicates that the adverse metabolic effects of sleep restriction don’t wane with time.
These changes seem pretty bad. It’s unclear to what extent they translate to long-term health effects (see the section below) but those are things you perhaps should not ignore when investigating whether sleep deprivation is bad for your health.
Guzey doesn’t talk about the supposedly U-shaped association between sleep and mortality on Theses on Sleep itself, but he has brought it up in a couple of other places (in the conclusion of his takedown of Walker’s Why We Sleep, and on a comment in the EA Forum) so I thought I’d tackle it here.
For those who don’t know, a lot of epidemiological studies seem to show that the association between sleep duration and mortality is something like this:
(This specific chart comes from Shen 2016).
But Kurina et al.’s “Sleep duration and all-cause mortality: a critical review of measurement and associations” finds that this U-shaped association is suspiciously restricted to a very specific type of study (emphasis mine):
One interesting pattern among studies using survey sleep measures is that all of the studies reporting U-shaped associations measured sleep duration with questions about typical nighttime sleep or 24-hour sleep (Table 2). None of the studies that asked about usual bedtimes and waking times reported a U-shaped association; rather, they reported either no association [12,22,23] or only a long sleep association [6,9,34,99], or, in the case of two studies of young to middle-aged Japanese men, only a short sleep association [12,22]. That the U-shaped associations are exclusively found in studies asking about usual sleep duration may be informative and suggests the possibility of systematic response biases, with people in generally good health more likely to give a “normative” response (i.e., 7 or 8 hours) and those in worse health more likely to give a “non-normative” (shorter or longer duration) response.
It seems that you can’t take people’s reports of how many hours they sleep at face value. Further evidence of that is that studies have shown that people seem to give the same answers when asked how many hours they sleep and how many hours they spend in bed. Also, a substantial fraction of older adults (47% in this study) report sleeping >=8 hours a night, but when their sleep is actually measured, very few of them do, as pointed out in Kurina et al.’s paper.
Kurina et al. look into studies that actually measure people’s total sleep time, and report the following:
A study employing actigraphy among women 50 to 81 years of age (n = 444) concluded that the relationship between sleep duration and mortality was U-shaped [... but] death rates by more detailed sleep categories do not show a dose response for either side of the duration distribution. The top and bottom categories (<4.5 or >7.5 hours) have relatively low mortality, albeit with small numbers, and the highest mortality risk was observed in women sleeping either 4.5—5 hours or—interestingly—between 7 and 7.5 hours.
Neither of the two studies employing polysomnography reported significant associations between sleep duration and mortality [27,36]. In both studies, sleep duration was dichotomized at fewer than 6 and 6 or more hours, precluding the possibility of finding a U-shaped effect.
This isn’t exactly strong evidence that sleeping too much or too little is not harmful. This review only mentions three studies examining the effect of measured sleep on mortality, and two of those didn’t record sleep duration in a way that would make them able to find a U-shaped relationship. Moreover, all of these naturalistic studies probably have substantial range restriction — they mostly involve elderly or middle-aged subjects, many of whom can probably sleep as much as they want, and it’s fairly plausible that very few of those people manage to consistently sleep so much or so little that it’s harmful. Also, they measured sleep for one night only, and the study equipment might have disrupted the sleep of subjects.
However, this review does provide evidence against six hours of sleep being associated with the lowest mortality, as Guzey has hypothesized before (as well as evidence against eight hours of sleep being associated with the lowest mortality, of course). And thus, most importantly, it also provides evidence against moderately short or moderately long sleep being harmful.
So here are my credences on a few relevant object-level claims:
I’d be happy to bet on reasonable operationalizations of those statements at those odds (unless I change my mind, in which case I’ll probably edit the credences listed here).
I thought I’d bring this up, since it affects how harmful we should expect sleep deprivation to be in expectation. Two years after being hospitalized for a manic episode, less than half of people regain their premorbid occupational and residential status, and the hospitalization rate of mania is pretty high, so manic episodes seem to screw people over really badly for a long time.
And sleep deprivation might risk triggering mania if you have bipolar or a high risk of getting it. A night of total sleep deprivation seems to be able to trigger full-blown mania in a substantial percentage of people with bipolar disorder (even those currently depressed) and even cause mania-like behavior in healthy subjects. Moreover, a shift towards mania or hypomania after a short night of sleep seems common in bipolar patients.
Given how bad mania is, it might be a good idea to try to decrease even a relatively small chance of getting it, so those at a high risk of getting bipolar disorder should probably consider these effects before experimenting with sleep restriction.
I collected a few amusing anecdotes about sleep deprivation from r/NewParents.
From this thread, titled “Tell me you’re sleep deprived without telling me you’re sleep deprived..”:
I just unzipped my 1 month old’s sleeper to expose his nipple so I could feed him…… 🤨
My husband attempted to hand me a cat to nurse.
"There was 120ml in the bottle, there is now 50ml in the bottle, so she's drank...Okay, this isn't that hard, there was 120 in the bottle, there is now 50 in the bottle so she's had...Right the bottle has 50ml, she's drank 120 so there should be.. no, she's drank 50 there's 120 left so, NO!there was 120 in the bottle, there is now 50 and it goes 50, 60, 70, 80, 90, 100, 110, 120 so she's had 120.NO! "i genuinely gave up and used a calculator
"There was 120ml in the bottle, there is now 50ml in the bottle, so she's drank...
Okay, this isn't that hard, there was 120 in the bottle, there is now 50 in the bottle so she's had...
Right the bottle has 50ml, she's drank 120 so there should be.. no, she's drank 50 there's 120 left so, NO!
there was 120 in the bottle, there is now 50 and it goes 50, 60, 70, 80, 90, 100, 110, 120 so she's had 120.
i genuinely gave up and used a calculator
From “Finish the sentence: I was so sleep deprived I....”:
Filled the dryer full of wet clothes and tried to turn it on via the microwave sat above it
...ran into a laundry basket and said "excuse me" to it.
Turned on the Keurig to make my coffee and walked away without noticing that I forgot to put my mug under it. The worst part is I've done this 3 or 4 times now.
Forgot to put a new diaper on after taking dirty one off. Baby went commando for a while.
From “Funniest thing you’ve said while sleep deprived in the dead of night”:
Nothing will ever top my husband waking me up saying "please take the baby I can't stay awake any longer" and gently passing me a very pissed off cat that had been asleep on his lap. Note, cat weighed twice what our newborn weighed. When I told him that was a cat he looked terrified and went "but then where's the baby?!"
My husband and I woke up to our 5-month old crying and he said, “Is that ours??” Yes, my good sir, that is in fact our baby.
It was my turn to wake up for a feed and my wife woke up first so said “babe, wake up she’s crying” and I responded “what? who the hell would be crying in our house?” It was 2 weeks after our daughter got home and she’s our first 🙃
(Let me know if you think something should be added here that hasn't been.)
This study looks for publication bias in the literature and says the following about what they found: "Evidence for publication bias was observed for the overall effect and the effect on measures of sustained attention; see Table 3. However, the impact of such publication bias on the effect appears to be minimal as another 75 studies with an effect size <0.0 would have to be added to result in a small overall effect size (g < −0.200)."
Orwin’s fail-safe N was used to calculate that number.
Note that the β for cumulative days of restricted sleep is negative, providing evidence against Guzey’s hypothesis that cognitive adaptation occurs after several days of restricted sleep, at least in the timespans investigated in the studies included in that meta-analysis.
Importantly, although this meta-analysis included total sleep deprivation studies, the numbers reported in the sentences I quoted are for partial sleep restriction only.
This is a very important caveat. People with mania will feel perfectly comfortable and productive while sleeping very little.
70% of 84 hunter-gatherers studied in 2013 slept less than 7 hours per day, with 46% sleeping less than 6 hours.
70% of 84 hunter-gatherers studied in 2013 slept less than 7 hours per day, with 46% sleeping less than 6 hours.
The study in question also found that the hunter gatherers spent 8-9 hours in bed each night. Sleep duration was measured using those Fitbit trackers that always tell you that you only slept four hours when you’re sure you slept about eight hours. If you move around in your sleep then the tracker assumes that you are awake.
This is an important point. When discussing sleep we have to both look at sleep as measured by devices (that do notice awake times during the night that aren't remembered) and at time in bed.
It's plausible that 7 hours of sleep are good for the average person while 8 hours in bed are necessary to achieve that for the average person.
I love the thought and research you've put into this, and I'm excited to see this dialogue continue.
When Guzey posted his "Theses on Sleep," I spent a lot of time going through meta-analyses and considering whether the underlying studies were sound. I talked about what I found in the comments there, and I wonder if you got a chance to read them?
I didn't look at the meta-analyses you cite here. The ones I did look at, though (Pilcher and Huffcutt on cognitive impairment, and Irwin, Michael R., Richard Olmstead, and Judith E. Carroll on inflammation), for me surprised me with how unconvincing they were when I looked under the hood. I think it would be valuable to read some measured reviews of individual sleep research metastudies.
Based on my experience with these two meta-analyses, simply being shown additional meta-analyses in this field finding a cognitive impairment effect doesn't update me much in the direction of there being a real issue. I would need to be confident that the studies it chose to analyze were relevant to the question at hand.
One of the distinctions Guzey made that I think was important was the difference between work-related fatigue and sleep deprivation. Many SD... (read more)
One of the distinctions Guzey made that I think was important was the difference between work-related fatigue and sleep deprivation. Many SD studies are on resident doctors at the end of 24-hour shifts. They are experiencing both work-related fatigue from a notoriously taxing job and sleep deprivation. As such, if we care about SD as opposed to fatigue, then such studies are hopelessly confounded as far as relevance for our specific research question.
I do think that that's an important distinction. Note that most of the studies included in the sleep restriction meta-analyses I quoted (all but one, in fact) are not on resident doctors, and, as far as I know, they pretty much exclusively examine the effect of sleep restriction (sleeping fewer than 6 or so hours per night) rather than the effect of staying awake for an abnormally long time.
I didn't look at the meta-analyses you cite here. The ones I did look at, though (Pilcher and Huffcutt on cognitive impairment, and Irwin, Michael R., Richard Olmstead, and Judith E. Carroll on inflammation), for me surprised me with how unconvincing they were when I looked under the hood.
I did actually cite Irwin, but note that my conclusion... (read more)
I didn't notice that it was you I was originally responding to - I apologize for the oversight! I also want to emphasize that I agree with you on some of your responses to Guzey. I think a lot of his arguments are weak, his Reddit- and self-supplied supporting evidence shouldn't be stacked up against peer-reviewed controlled sleep studies, and some of the argumentation comes off as a conspiratorial strawman (i.e. "At this point, I’m pretty sure that the entire “not sleeping ‘enough’ makes you stupid” is a 100% psyop.").
In the first of the meta-analyses you posted (Lowe, Safati, and Hall), I see some supporting evidence for your position, and some complicating factors. From the abstract:
This effect held for executive functioning (g = −0.324, p < 0.001), sustained attention (g = −0.409, p < 0.001), and long-term memory (g = −0.192, p = 0.002). There was insufficient evidence to detect an effect within the domains of attention, multitask, impulsive decision-making or intelligence.
So first, let's acknowledge that they found significant, moderate effects in two areas that we may very well care quite a lot about! However, the long-term memory effect would be conventionally categori... (read more)
I am also interested, especially in "what tools can help people develop data for themselves, that can be aggregated in useful ways?" One way I think sleep science and most everything else goes wrong is in looking for the modal human answer, ignoring how the right amount of sleep/nutrient X/exercise/etc vary between humans and for the same human over time.
I wear an Oura ring and and Apple Watch with a sleep app. Both of these devices agree on when I'm underslept, and they are both correct; when my watch says I'm underslept, I feel stupid and tired and my chess.com scores plummet. My chronic pain condition is also much worse when I'm underslept. Additionally, I do not use an alarm clock, so my body will claw back the sleep it needs. If I only get 6 hours two nights in a row, I will sleep 9 hours the following night, but I habitually wake up after 7-8 hours. I can observe these patterns in my recorded sleep data, and they are robust over long stretches of time.
I say all of the above because frankly my own personal experience and data tracking is sufficient evidence for me to basically disregard any sort of thesis claiming that I need less sleep. Maybe you need less sleep, I don't know. Do the experiment, try to sleep less for a couple of days, see if you physically implode. I would put money on the "you will probably learn that you were already pretty in tune with your body's needs" outcome.
I think Natalia brings up a lot of important, true, points here, and I'm really glad she wrote this post. I also stand by what I said when I curated Alexey’s post, that while I was doubtful on any particular conclusion I thought he was pointing at real deficits in current models and I was excited to see those explored so they could be eventually filled in. My current guess (having not deeply investigated the evidence for either post) is that this post is closer to the literal truth, and Alexey’s post is pointing in a more useful direction (but we will get there in part by people pointing on the parts that are false, via posts like this).
The version of Alexey’s theses I most broadly support is “we treat sleep like one thing, when it is in fact multiple things with multiple purposes”. Natalia calls this epicycles, I agree with AllAmericanBreakfast that it’s more like scurvy before the vitamin C paradigm. There’s a real thing there, but without the paradigm it looks incredibly fake and exactly like epicycles. In general I think distinguishing ideas analogous to pre-vitamin-C scurvy from ideas like epicycles is one of the Hamming problems of science, and would cheer development in the ... (read more)
[ETA: to be clear, I’m not criticizing the thesis of SMTM’s post here, just pointing out a factual error]The linked SMTM post is misleading.
Here is the vitamin C content per 100g of some relevant foods, which I found after a few minutes of searching on Google:
I couldn’t find information on the vitamin C density of polar bear livers in particular, but from these values, it seems far from clear that polar bear livers are more similar to lemons than limes in that respect. The vitamin C contents of limes and lime juice do not stand out in that list.
Moreover, it seems that it only takes about 10mg of vitamin C per day to prevent scurvy, and the Manual of Nutritional Therapeutics says that the same daily quantity is enou... (read more)
The version of Alexey’s theses I most broadly support is “we treat sleep like one thing, when it is in fact multiple things with multiple purposes”. Natalia calls this epicycles
That sleep is multiple things is not something I am arguing against. (In fact, I don’t recall that being a point in Guzey’s post). What I uncharitably called “epicycles” was the additional complexity Guzey’s model has to have to explain why so many people feel dumber after sleep restriction, and why experimental studies say that sleep loss causes cognitive impairments, when ““not sleeping ‘enough’ makes you stupid” is a 100% psyop.”
It’s pretty clear to me that sleep has multiple effects, and that it might be the case that there’s something with all of sleep’s good effects and none of the bad ones that just hasn’t been discovered yet. Maybe digital people would only have to spend the subjective equivalent of a few seconds per day shut down in order to renormalize their weights or whatever, or might not need to be shut down ever at all to maintain their performance.
But I don't think that is incompatible with the object-level claims in my post, any more than saying “humans don't live to be 200 years old” ... (read more)
I've been meditating on the broader relationship of this post, and Guzey's, to the idea of instrumental rationality and the question of what rationality is good for. A idea is that instrumental achievement is bottlenecked by akrasia.
When we study sleep, we're really studying one aspect of fatigue, which is similar if not identical to akrasia. We can think of fatigue as being subdivided into physical and experiential components. Like other forms of fatigue, sleep pressure manifests both in physical brain structures and in our conscious, felt experience.
Sleep may be a specific solution to a specific physical or felt need, and our sense of sleep pressure may be well-tuned by evolution to indicate the amount of sleep required for optimal function. Sleep may also be a nonspecific solution to these needs, and sleep pressure may be only marginally attuned to the timing and duration of required sleep.
More broadly, we have agentic goals. To accomplish them, we generally must maintain our minds and bodies in order to work efficiently and maintain motivation, while also freeing up time to do that work.
It is possible to carefully calibrate many of our routines. For our diets, we can count calo... (read more)
(I'll reply in more substance by the end of the week -- have a big deadline coming up this Thursday)
From skimming the post, three parts stand out to me
1. the fact that acute sleep deprivation relieves depression in ~50% of people with depression seems completely unaddressed and Natália's section about bipolar people seems to imply that this would not be happening. I specifically noted in this the section Natália addresses by writing:
Lack of sleep is such a potent trigger for mania that acute sleep deprivation is literally used to treat depression. Aside from ketamine, not sleeping for a night is the only medicine we have to quickly – literally overnight – and reliably (in ~50% of patients) improve mood in depressed patients
One of Guzey’s theses is that “[o]ccasional acute sleep deprivation is good for health and promotes more efficient sleep.” His argument supporting that thesis is pretty much that, because some types of acute stress (such as exercising and fasting) are good, and acute sleep deprivation causes acute stress, then acute sleep deprivation is also good. (Yes, that does seem to actually be the entirety of his argument in that section. You can read it yoursel
Natália doesn't set out to disprove all of your theses, but rather to put forth some counter-theses. She says:
I decided to write a post pointing out several of the mistakes I think he’s made, and reporting some of what the academic literature on sleep seems to show.
Read carefully, she neither claims that every point you've made is mistaken, nor to give a comprehensive review of the academic literature. So I don't think you can fault her for not addressing the point about the use of sleep deprivation as a depression cure. She's critiquing those theses of yours which she found weak, not issuing a comprehensive point-by-point criticism of your entire original post.
I think that you owe this level of care in interpreting her language, because you're insisting that she offer you that same level of care. You said:
people who sleep just 6 hours a night might have the lowest mortality
And then you complain when she rephrases this as:
six hours of sleep being optimal for mortality, as Guzey has hypothesized before (as well as evidence against eight hours being optimal for mortality, of course).
To my eye, these reflect approximately equal levels of imprecision, thought that's a purely subjective... (read more)
Natália's section about bipolar people seems to imply that [sleep deprivation's short-term antidepressant effects] would not be happening.
I disagree. I said,
A night of total sleep deprivation seems to be able to trigger full-blown mania in a substantial percentage of people with bipolar disorder (even those currently depressed) and even cause mania-like behavior in healthy subjects. Moreover, a shift towards mania or hypomania after a short night of sleep seems common in bipolar patients.
Here, I think it was clear that what I said is consistent with sleep deprivation having antidepressant effects, and it could even be interpreted as implying that it does. So I think it's misleading to suggest that this section implied that the antidepressant effect does not exist.
2. Your section arguing that occasional sleep deprivation is good for health makes no mention of its antidepressant effects, which were addressed separately earlier on in your post. I thought you were making a separate argument in that section, which is why I countered with an appropriate analogy. I merely think that the argument "sleep deprivation causes acute stress, therefore it's good" is weak, and that was my ... (read more)
Switching to mania from depression usually (though not always) means that the depressive symptoms went away. But I agree that my phrasing was poor and I’ll edit it.
I want to apologize for lack of proper engagement with the post and lack of replies to you as well as a high level of combativeness in the comments I did leave.
This stuff makes me anxious and I feel like I'm just unable to properly explain what makes me disagree so much with you.
My best attempt is that my takes are some combination of:
I found this reply unpersuasive.
By numerical point:
Deep skepticism of the sleep literature is fine, even if you rely on some sleep research yourself, but it's insufficient to respond to the objection of hypocrisy of relying on the sleep literature with "well, I'm really careful about which studies I use". You need to explain why the studies you use somehow avoid the methodological problems that cause you to reject other studies. If you don't, it seems like you are just cherry-picking supporting studies because they support you.
I have a tentative guess on why he's doing that, based on Scott Alexander’s post about trapped priors.
I’ll give an example of the basic problem outlined in the post myself, to spare you from having to read all of it before understanding my comment. Suppose that a physicist spends two hours trying to convince you that the Earth is flat. Would you see that as strong evidence that the Earth is flat? Personally, I’d see that as extremely weak evidence. Instead of updating much that the Earth is flat, the conversation would instead make me seriously consider the following more-plausible-to-me hypotheses:
Fair point, although I wasn't assuming any bad intentions, more like a hard-to-explain emotional intensity that seemed out of character for someone whose writing I am familiar with. But perhaps expressing my genuine surprise was not constructive—thanks. I removed this intro from my post.
Thanks for engaging. I hope we can figure out what our cruxes are.
On points 1 and 2: I still think you haven't addressed my counter-argument to points of that nature, which I've raised (1) in the post itself, (2) in my previous reply to you, and (3) in this comment. To reiterate some of it: you use sleep research to support some of your points, mostly in your review of Walker's book but also in Theses on Sleep, and it's not clear to me why research that shows that sleep deprivation is not as bad as people think is admissible evidence to you but research that shows that sleep deprivation is not harmless is not. I was, and remain, skeptical that you have a consistent and rigorous standard for what research you think is admissible and what research you think is not.
Just to reiterate: I believe that the points 4, 5.4.1, and 5.4.2 invalidate large chunks of sleep literature and are simply not possible under the default "sufficient sleep is good and necessary for proper functioning for normal people on the scale of a few days to a week".
Notice that my post does not argue against anything that is invalidated by 4, 5.4.1 or 5.4.2.
As I elaborated before in my post, 5.4.1 pret... (read more)
This isn’t as important as my previous reply (in which I address your object-level arguments), but I wanted to perhaps note that most of your points 1.1 through 1.4 sound, to me, more like an attempt to generate an emotional reaction in the reader than a good-faith effort at pointing out mistakes you think I’ve made or investigating object-level disagreements (although I could be wrong). I don’t recall criticizing you for not having an MD or something, or publicly speculating that you have never thought about [important meta-level epistemological consideration].
I understand that the fact that I did not take biology or neuroscience classes in college is evidence that I would not have a good understanding of sleep research, but I think it is perhaps important to keep in mind that argument screens off authority here, and it sounds plausible that, a lot of the time, domain experts in the area would acquire knowledge in it the same way I do (by reading meta-analyses and systematic reviews, or textbooks based on those). They don't have some sort of magical essence that makes them more knowledgeable than everybody else could become. They do original research, but not in every sub-ar... (read more)
Thanks for this post, I've curated it! Reason why include:
Conditional on this, cognition does not return to baseline levels after several months of sleep restriction: 78%
Does this mean you're conditionally claiming that several months of sleep restriction results in permanent damage to cognitive faculties, irreversible even after long-term restoration of normal sleep?
No. (Thanks for pointing out that that’s not clear). My model is that moderate sleep restriction harms cognition the following a day, regardless of how many nights of it you’ve had before; I’m much more uncertain about whether it causes permanent damage to cognition.
Anecdotally, since reading Guzey's post a month ago, I cut down my sleep from ~7.25 hours (5 nights 7.5 hours + 1 night 6 hours) to around 6.33-6.5 hours (1 night 7.5 + 2-3 nights 6). I found that doing just 6 hours 4+ days in a row led to noticeable tiredness, although I never tried just pushing through and seeing if I can get used to it.
Regardless, with the current sleep load, I feel pretty good, and I plan to continue it. However, I have noticed some rare working memory slip-ups, maybe one per day or every other day, that I don't think were as common before I dropped the sleep, although this isn't severe enough to make me want to stop.
There is something about Natália's and Guzey's interaction through your posts and in the comment section that doesn't feel right to me. I haven't been able to pin down exactly why I get this feeling but my best guess is that it seems like you are missing your actual disagreement.
To me it seems like you are both agreeing on the existing evidence is week. You bring up evidence that point in different directions sure but neither of you seem to bring up strong evidence.
However, you seem to have quite different beliefs on the matter. Natália says:
Our priors abo
Another odd discrepancy.
The largest single study in the Lowe meta-analysis is Banks (2010), which had 159/1688 of the participants (9.4%). In table 2, Lowe reports that Banks measured 1 day of sleep restriction. But Banks actually did 5 days of 4hr sleep restriction/4hr time in bed, followed by 1 "recovery" day of 0, 2, 4, 6, 8, or 10 hours of time in bed. It's unclear why Lowe coded it as 1 day of cumulative sleep restriction rather than 5-6. In addition, I don't understand how they would have incorporated effect sizes into their meta-analytic procedure.
G... (read more)
Thanks for the taking the time to look into my essay.
Here's what Mendonça writes in her first point that so conclusively demonstrates that the point I make is "misleading":
[Guzey's] evidence from bipolar disorder patients is not representative of what you see in the general population: both long and short sleep duration are associated with depression
The paper Mendonça cites looks at long-term long sleep and long-term short sleep, with their association with depression. My claim and my evide... (read more)
The paper Mendonça cites looks at long-term long sleep and long-term short sleep, with their association with depression. My claim and my evidence (from bipolar people) are concerned with short-term long sleep and short-term short sleep.
Your specific claim about depression was “depression triggers/amplifies oversleeping while oversleeping triggers/amplifies depression.” Nowhere in the section did you specify your claim was about short-term long sleep.
Your evidence, too, barely concerns short-term long sleep: depressive episodes last about five or six months on average, which is often not what people have in mind when they think about “short-term” oversleeping, and it's common for them to last a year or more.
It is further puzzling that in her refutation of my argument she:completely ignores the relationship between sleep and mania (i.e. she ignores one half of my argument and only discusses the part about depression).completely ignores the fact that in ~50% of ALL people with depression (not just bipolar), short-term short sleep relieves depression.
It is further puzzling that in her refutation of my argument she:
I don't disagree with you on the claim that sleep restriction or deprivation often causes mania, and can adequately treat de... (read more)
In the interest of simplicity, I'm going to look at individual pieces of your and Natalia's counterarguments. I won't do it all at once, but I'll try to be thorough over time. I'll be separating my analyses into separate comments.
To start with, you say:
Here's what Mendonça writes in her first point that so conclusively demonstrates that the point I make is "misleading":[Guzey's] evidence from bipolar disorder patients is not representative of what you see in the general population: both long and short sleep duration are associated with depressionThe paper Mendonça cites looks at long-term long sleep and long-term short sleep, with their association with depression. My claim and my evidence (from bipolar people) are concerned with short-term long sleep and short-term short sleep. That is, Mendonça's paper is simply not overlapping with with what I write about or what the evidence she calls "misleading" is concerned about.
The paper Mendonça cites looks at long-term long sleep and long-term short sleep, with their association with depression. My claim and my evidence (from bipolar people) are concerned with short-term long sleep and short-term short sleep. That is, Mendonça's paper is simply not overlapping with with what I write about or what the evidence she calls "misleading" is concerned about.
To break this into parts:
My claim and my evidence (from bipolar people) are concerned with short-term long sleep and short-term short sleep.
There are several types of bipolar, including bipolar I and bipolar II.
Bipolar I Disorder is defined by manic episodes t
I think the value was in the interesting idea rather than being particularly rigorous
The effects of napping found by the meta-study you linked are more complex than your quote suggests:
The literature reports that the benefits of daytime napping may last 2.5 h , with conflicting results during the sleep inertia period, i.e., after awakening [55,69]. These findings were in accordance with results from our study, in which the positive effects of the nap were mainly 30–120 min following awakening. For the 30 min after napping, results were mitigated and variable, depending on sensitivity analyses, reflecting putative effects of sleep inert
I'm surprised that tinkering with sleep is even an area of interest in LW circles. It's a classic Chesterton's fence not to mess with. Short-term sleep deprivation is fine and happens all the time, chronic sleep deprivation is bad, don't do it, focus on some other ways to squeeze more time out of the day, if that's what one is after. Leave the sleep research to the professionals, it's not a low-hanging fruit.
(Unless you intentionally sleep deprive to trigger bipolar hypomania and are reckless enough to risk it turning into a full mania.)
Chesterton's fence means that you want to investigate strange-seeming barriers, rules, and norms before tearing them down permanently, not that you should leave them in place unquestioned :) And the claims you make here are precisely the questions we are trying to address.
Sleep research provides an interesting exercise in rationality, because it touches on so many pertinent challenges. There's instrumental reasoning with imperfect information, figuring out how to conceptualize the issue, mechanistic reasoning, critical interpretation of scientific literature -- it's all there. Personally, I think it's a great rationalist exercise.
Your advice here is too imprecise to be debatable. What's the line between normal sleep variation, individual sleep differences, and "playing with it?" If we don't feel tired (as in mania), are we "playing with sleep" if we simply stay awake, as we feel inclined to do, or are we "playing with sleep" if we indulge in staying up late?
When you say that it's "bound to backfire," can you turn this into a claim precise enough to make into a bet?
When you say it's "best done professionally," do you mean that we should leave it to professional sleep researchers to run such studies, or that we should simply get the FDA-recommended amount of sleep and not ask why?
If you can make your claims precise enough to match the level of care, thought, and rigor on display here and in guzey's original post, I'd love to engage further!
I don't think your 'our priors about sleep research should be high' argument holds, for the simple reason that everyone knows, now, that you're supposed to be tired and grumpy when you get less than "your eight hours". There is almost certainly a placebo effect in play, which means that you may well be allowing the sleep research itself to affect your priors about the plausibility of the sleep research!
This doesn't undercut the rest of the post, but I do think "Occasionally stubbing your toe is good for health and promotes more efficient toe healing" is unfair. Lots of people believe that acute stress in the form of exercise, infection, fasting, or extreme temperatures is good for them, and sleep deprivation seems a lot more like those than like stubbing a toe. Of course those beliefs could be wrong, or sleep could not be a member of the set, but if the hypothesis were incorrect I think it would be a normal kind of incorrect, not something as ridiculous as "breaking a bone is good for you".
I agree with Elizabeth that it intuitively feels like SD fits more with things like exercise and infection than things like toe-stubbing. I did not have a ready-made answer before you asked the important question "why?," and I think that means you should discount this somewhat as rationalization. With that caveat, here goes!
First, let's look at some of the underlying physiological impacts of these potentially "good stressors."
Re the point that mania is very bad, I agree, but people should know that not all mania is associated with bipolar disorder.
Sleep is not required for memory consolidation.
That's very puzzling to me. Why do babies need so much sleep then? I assume memory consolidation is a central part of the learning process, is it not? Or do babies need to sleep a lot for other reasons than learning stuff? Of course what a baby's brain goes through is pretty massive, but is it not the same (at least partly) as what an adult's brain goes through when learning something, just at a different scale?
Does this really count all sleep time (including naps) or only night sleep? It sounds strange if it counts all sleep time. At least in conjunction with the claim that hunter-gatherers "worked" fewer hours than modern humans (I, of course, assume that modern hunter-gatherers have a life similar to ancient ones). In addition, there doesn't seem to be much to do when it is dark -even when you have fire-; it is very unlikely not to fall asleep ... (read more)
Currently not in a frame of mind for focus but want to ask about two related questions. A quick search didn't seems to find some key words so don't think you discussed in the post (but again, not well focused right now so maybe fit better with some of the quotes you conclude with ;-)
First, seems like there might be a opposing result related to limiting sleep and the reverse flow for cleaning out toxin accumulation in the brain. Did you find any mention of that aspect?
Second, and I have zero basis for the thought other than it was something that popped into... (read more)