Moderate Alcohol Intake Won't Save Your Brain
/Misinterpretations of the study have lead to some erroneous conclusions.
This week, in solidarity with many people in this country, I am pretending that coronavirus doesn’t exist and talking about a paper that has absolutely nothing to do with that horrible strand of RNA raining destruction around the world.
I apologize for being flip – it’s been a frustrating time in the world of epidemiology.
But it’s ok to take a break here and there, and this paper, appearing in JAMA Network Open caught my eye, not for the purity of the science or the methods per se, but because the conclusion comported with something that, in the face of lockdowns and shelter-in-place orders, I really wanted to be true. Drinking alcohol might be good for you.
I recognize the bias – cherry picking studies because they align with what you want is a terrible way to report on science. But fear not, loyal viewers, I have not fully abandoned my principles. In fact, after reading the paper I’m not any closer to convincing myself that a couple of Dog Fish Head’s a night are a good thing.
“I know doctors say you are supposed to have a glass and a half, but I just can’t drink that much” - Marge Simpson
Researchers examined data from the Health and Retirement survey, a nationally representative sample of US adults. More than 19,000 individuals had biennial surveys of cognitive function looking at domains of mental status, word recall, and vocabulary. You had to have at least three such surveys to make it into this analysis, allowing for modeling of cognitive trajectory. Of course, individuals also self-reported on their drinking habits. They were classified as non-drinkers, low-moderate drinkers, and heavy drinkers based on this rubric.
Now, the analysis I wanted was a nice mixed-effects model, which would examine the rate of drinking over time as the independent variable and cognitive function over time as the dependent variable with adjustment for a slew of relevant confounders like age, socioeconomic status, comorbidities, smoking history, medication usage, etc.
But this is not what I got.
The researchers used a data-driven approach to model cognitive trajectories. Basically, you feed the cognitive data and time into an algorithm, and it tries to fit all that data into discrete groups – based on some information theoretic principles. You don’t know going in, how many groups it will find. It might find a group characterized by rapid cognitive decline or slow cognitive improvement. The data drives the grouping. Cool.
These are not the groupings you are looking for.
But what this data led to were two groups as you can see here – consistently low cognitive trajectory and consistently high cognitive trajectory.
This is our first sign that we’re not going to get the information we want. It seems there is not enough variation in the study cohort to determine how alcohol use may change your cognitive trajectory.
In other words, what the data shows, is that people who started off with good cognitive scores kept good cognitive scores and those who started off worse, stayed worse.
Risk of being in the persistently low cognitive trajectory group.
This does not bode well for my dream analysis. I am not surprised that most people stay in their cognitive lane. Regardless of which lane I am in, what I care about is whether my drinking is going to change my outcome.
The researchers showed, after adjustment for age, sex, race, ethnicity, marital status, smoking status, and BMI, that low-to-moderate drinking was associated with a significantly lower risk of being in the persistently low cognitive group.
A hint of what could have been.
Again, I don’t find this terribly interesting. Because I don’t want to know how likely it is that I’m in the persistently low group, I want to know how to get out of it.
To be fair, there was a small analysis looking at rate of change in cognitive score over time that for whatever reason was given short shrift in the discussion. It showed that, after adjustment, people who drank more had improved cognitive scores compared to those who never drank.
The authors offer some interesting biologic rationale as to why drinking might be protective, focusing on brain-derived neurotrophic levels and neural plasticity.
But let’s be honest, really, low-moderate alcohol drinking is likely a sign of socioeconomic status, which can be very hard to adjust for – and wasn’t adjusted for at all in this study as far as I can tell. Drinking a couple glasses of wine a night takes disposable income, and likely a social structure (like marriage, family, and friends) that promotes health and cognition.
Observed racial differences are always sociological, not biological. Fight me.
An analysis stratifying the results by race confirms this supposition for me. The researchers found that the protection of low-moderate drinking was only seen in white people. No such effect was seen in black people.
When something like this happens in a study, it is really a dead giveaway that there is a sociologic phenomenon driving this rather than a biologic one, because there is no reason to think that there are substantial differences in the effect of alcohol on the brain between black and white individuals.
So I am left, alas, without confirmation that the second beer of the night is good, healthful behavior. It’s probably not. But it’s probably not too harmful either. And hey, if we’re all destined to stay in our cognitive lane, we might as well enjoy the ride.
This commentary first appeared on medscape.com.