A recently published analysis combined data from nine studies to create the "life course trajectories of alcohol consumption" for folks in the UK. The study marks the first attempt at estimating, from longitudinal data, how our drinking habits change with age.
The results of the study, which was led by University College London epidemiologist Annie Britton, appear in the latest issue of the journal BMC Medicine. They're open access, too, so be sure to check them out for yourself.
The graph above reflects the projected weekly drinking habits of an average UK man and woman. The curves are actually predictions, based on 9 separate longitudinal cohorts and a a combined sample size of 59,297 people and 174,666 alcohol observations. In other words: No, these researchers did not monitor the lifelong drinking habits of one big cohort of people for the better part of a century. What they did was combine some pretty big data sets, all of which were amassed over extended periods of time, and perform some fancy statistical analyses. The resulting graph provides us with a unique perspective on the dynamic nature of alcohol consumption over a typical lifetime.
So, how do you read this graph? The x-axis, which denotes age, is pretty clear. But what about the y-axis?
Because different beverages contain different quantities of alcohol by volume, the UK, like the United States, has a standard by which it quantifies alcohol consumption. One "UK unit of alcohol" is equal to 8 grams of pure ethanol. Here in the U.S., we measure not in units, but in what are called "standard drinks," which the National Institutes of Health defines as "any drink that contains about 14 grams of pure alcohol." A standard U.S. drink is therefore equal to 1.75 UK units of alcohol, and is roughly equivalent to a 12-ounce beer, a 5-ounce glass of wine, or a 1.5-ounce shot of hard liquor. The Washington Post's Christopher Ingraham took the liberty of converting UK units into standard U.S. drinks, and translating the figure at the top of this post into the color-coded graph you see here. Note that these graphs convey little information about day-to-day drinking habits also revealed elsewhere in the study. For instance, in men especially, total alcohol consumption decreases with age, but frequency of consumption actually increases, as our drinking habits become less of a weekend-binge thing and more of a glass-of-wine-at-dinner thing.
From Ingraham's graph, we can see that for the average U.K. man, alcohol consumption is projected to peak at around 25 years of age at roughly 13 drinks per week. Women, by comparison, drink considerably less, topping out at a little under four drinks per week.
The researchers also concluded that "non-drinkers were uncommon, particularly among men, where the proportion remained under 10% until old age, when it rose to above 20% among those aged over 90," though Ingraham explains why this finding likely doesn't hold outside of the United Kingdom:
Given that the authors analyzed studies from the U.K., these findings don't generalize perfectly to an American drinking context. For starters we know that there are a lot more non-drinkers here — up to 30 percent of the population, by some estimates. And Americans drink less than our British counterparts overall, according to the World Health Organization.