There are a lot of claims about how alcohol affects the body, and some sort of "heavy drinking is bad for you but light or moderate drinking is better than no drinking" is a common one. I've not paid a lot of attention to these, however, since non-drinkers as a group include a bunch of people who've given up alcohol due to health-related issues. I was interested, however, to see a study ( Tian et al. 2023) that compares light and moderate drinkers to people who haven't ever been drinkers. Unfortunately, after getting into the study I don't think it tells us much and I haven't updated my views here.

The study finds:

Compared with lifetime abstainers, current infrequent, light, or moderate drinkers were at a lower risk of mortality from all causes, CVD, chronic lower respiratory tract diseases, Alzheimer's disease, and influenza and pneumonia. Also, light or moderate drinkers were associated with lower risk of mortality from diabetes mellitus and nephritis, nephrotic syndrome, or nephrosis.

To get this association they analyzed data from the NHIS survey, which includes questions on drinking habits, and the linked death records.

As you might expect, lifetime abstainers look quite different from light and moderate drinkers. For example, 26% of lifetime abstainers had less than a high school education, while only 10% of light or moderate drinkers did. The lifetime abstainer group is also a lot older (22% 65+ vs 10% or 13%), more female (66% vs 50% or 27%), more Black (17% vs 9% or 8%), more Hispanic (19% vs 12% or 10%), more nonsmoker (82% vs 56% or 44%), and more physically inactive (69% vs 48% or 43%). See the full table. Visually:

These are really big!

Now, they did adjust for these, along with many other differences between these groups:

The above-mentioned associations were investigated by adjusting for the following covariates: age, sex, race, or ethnicity (model 1); model 1 plus education level, physical activity, body mass index, smoking status, hypertension, heart disease, stroke, cancer, diabetes, asthma, emphysema, or chronic bronchitis in a separate model (model 2).

The problem is, there could easily be other important confounders. If something they are not adjusting for leads to both abstinence from alcohol and higher mortality, they aren't able to distinguish that from the causal effect of alcohol on mortality.

They do explicitly list this concern, the first one in their list of limitations, and it's always something I'm worried about with correlational studies. But this is worse than usual: the known differences between these groups going into the study are so large that I am very skeptical that adjusting for these is enough to cover the unknown differences. So I haven't updated my views appreciably from this study.

(I don't drink, but not for health reasons.)

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Have you ever seen a study like that break down the abstainer group by their reasons for abstaining?

I wonder if we'd see different health outcomes corresponding to different rationales. I'd expect to see at least some difference between "I've seen it cause severe problems for an immediate family member" vs "religious or spiritual beliefs tell me not to" vs "I don't have the financial or social opportunity to" and so forth.

n=1: "because I highly value my brain as it is, and alcohol (and other drugs) seem to mess with the brain in ways that are presumably bad" (this opinion came from middle school), and, later, "because I have two uncles who've struggled with alcoholism".  Also, some people have assumed I'm a Mormon (I'm an atheist).

My guess would be that:

  • the direct biological harms of alcohol are roughly linear, i.e. one drink a week is about 1/7 as harmful as seven drinks a week, which in turn is about 1/7 as harmful as forty-nine drinks a week;
  • the psychologically mediated benefits of alcohol (through reduced anxiety, improved socialization, etc.) quickly rise up to a few drinks a day, then plateau (and even reverse at very high doses)
  • when you subtract something like atan(x) from a straight line you may or may not get a minimum at x slightly greater than zero, depending on the slopes involved

More conjecture than anything else since I haven't looked into myself but I've also heard that some of the "benefits" from alcohol are secondary to the actual act of consuming alcohol.

Drinkers tend to get out more going to bars, clubs, etc. That alone could contribute to a myraid of things; exposure to more germs due to the close quarter nature of those environments, psychological benefits of being more social (increased well being, decrease in stress, etc).

I've seen people go as far as saying the majority of alcohol's benefits are from these secondary factors. Again conjecture but nonetheless. I've not seen data or evidence to back this up, just sort of follows sensible reasoning. Grains of salt here surely.

There is a mechanistic explanation. Alcohol is a blood thinner. Blood thinners protect from ischemic heart disease, which is such a large portion of mortality a small improvement can make up for worsening of all other causes. Which is exactly what we see in the observation.

It's that simple.

The paper claimed that in addition to a decrease in people dying from heart conditions there were also decreases in deaths from "chronic lower respiratory tract diseases, Alzheimer's disease, and influenza and pneumonia."

Since those are rare causes of deaths, they don't matter and they're hard to measure. Also, this is a small study, so I trust earlier studies more.

Since those are rare causes of deaths, they don't matter and they're hard to measure.

Per the paper's table 2, deaths in the lifetime abstainer group were, as a fraction of all deaths in the group:

  • CVD: 13,562 (34%)
  • Cancer: 8,169 (20%)
  • CLRT: 2,030 (5%)
  • Alzheimer's:1,730 (4%)
  • Diabetes: 1574: (4%)
  • Accidents: 1331 (3%)
  • Flu and pneumonia: 952 (2%)
  • Kidneys: 895 (2%)

Light drinking mortality relative to lifetime abstainers, with full controls ("model 2"):

  • CVD: 0.76 (0.73–0.80)
  • Cancer: 0.86 (0.81–0.91)
  • CRLT: 0.68 (0.60–0.76)
  • Alzheimer's: 0.68 (0.59–0.78)
  • Diabetes 0.72 (0.61–0.84)
  • Accidents: 0.96 (0.83–1.11)
  • Flu and pneumonia: 0.63 (0.52–0.75)
  • Kidneys: 0.66 (0.54–0.81)

This really doesn't look like "the study is great, and the underlying effect is entirely alcohol reducing CVD".

this is a small study, so I trust earlier studies more.

There are 40k lifetime abstainer and 26k light drinker deaths; how much bigger are the studies you prefer?