August 29, 2018

Is one drink per day really dangerous? Behind the hype of a major new study.

Daily Briefing

    Last week, The Lancet published an analysis examining the benefits and harms of alcohol worldwide, and the news media framed its findings in alarming tones, warning that "there's no safe amount of alcohol." But Aaron Carroll in the New York Times' "The Upshot" explains why the actual takeaway is "much less newsy and much more measured."

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    About the analysis

    For the analysis, researchers reviewed data on the risk of individual and population-level alcohol consumption from 694 sources, as well as data on the risk for 23 alcohol-related conditions from 592 prospective and retrospective studies from 195 countries. Using the data, the researchers estimated current levels of alcohol consumption around the world—adjusting for tourism and unreported alcohol consumption—and predicted the global harm of alcohol.

    Overall, the researchers found harms from alcohol were the lowest when people did not consume alcohol, and they found harms increased with each additional alcoholic drink consumed per day.  

    The researchers provided a chart showing that the risks for the alcohol-related conditions increased as alcohol consumption rose from 0 to 15 drinks.

    Specifically, the researchers found for each group of 100,000 people who consumed one drink—defined as 10 grams of pure alcohol—per day, 918 can expect to develop one of the 23 alcohol-related conditions in a given year. For each group of 100,000 people who do not consume alcohol, the researchers found the risk of developing one of the 23 alcohol-related conditions was still high, at 914.

    Those numbers increased with the number of drinks consumed per day. The researchers wrote that, while light and moderate alcohol consumption is associated with reduced risks for diabetes and heart disease, alcohol consumption overall is associated with increased risks for cancer and tuberculosis risks.

    As such, the researchers wrote, "The conclusions of the study are clear and unambiguous: Alcohol is a colossal global-health issue and small reductions in health-related harms at low levels of alcohol intake are outweighed by the increased risk of other health-related harms, including cancer."

    Why the analysis should be interpreted with caution

    Even so, according to Carroll, it's important to be skeptical when reading claims in the news such as "There's No Safe Amount of Alcohol."

    He notes that the study—through no fault of the researchers—contains several "limitations ... that warrant consideration." The study was a meta-analysis of previously conducted observational studies—not a new clinical trial. As such, the researchers were unable to control for several factors that could account for differences in health among drinkers and nondrinkers, such as smoking or income levels.

    He writes, "[W]hen we compile observational study on top of observational study, we become more likely to achieve statistical significance without improving clinical significance. In other words, very small differences are real, but that doesn't mean those differences are critical."

    Carroll also notes that the analysis was conducted at the "population-level ..., but the results are being interpreted at an individual level." As such, the analysis "merg[es] ... 23 alcohol-related health issues together" when "not everyone experiences them at the same rate."

    He further explained that the analysis' findings on alcohol consumption, namely that it increases a person's risk for several diseases, does not necessarily mean that no one should ever consume alcohol.

    "Consider that 15 desserts a day would be bad for you. I am sure that I could create a chart showing increasing risk for many diseases from 0 to 15 desserts," Carroll writes, which "could lead to assertions that 'there's no safe amount of dessert.' But it doesn't mean you should never, ever eat dessert."

    What is a safe level of alcohol consumption?

    Without a true clinical trial examining the issue—and controlling for various health factors—Carroll writes "we just don't know" what the safe level of alcohol consumption is for most people.

    "If these studies are intended to drive population-level policy, we should use them as such, to argue that we might want to push people to be wary of overconsumption," Carroll writes, adding, "Too many people interpret them individually, however, with panic-inducing results" (Carroll, New York Times, 8/28; Hamblin, The Atlantic, 8/24).

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