Recent methodologically sound studies find little evidence for the “J-shaped” curve suggesting low amounts of alcohol protect against death. Researchers in the UK examined electronic records for alcohol consumption among 1,937,360 patients age ≥30, and outcomes in 4 national databases. Analyses were adjusted for age, sex, smoking, and socioeconomic status. People with “moderate” consumption were the reference group.
- Cardiovascular disease (fatal and non-fatal) and mortality were lowest in the “moderate” group (e.g., those described as consuming “alcohol within sensible limits” or as “light drinkers”); the hazard ratios (HR) for the non-drinking group (“teetotalers” or “non-drinkers”) were 1.1 and 1.2, respectively.
- For unstable angina, the only group that differed was non-drinkers (HR, 1.3). For sudden death, former drinkers (HR, 1.4) and people with heavy consumption (HR, 1.5) were at risk; non-drinkers and people with “moderate” consumption were at similar risk. Non-drinkers and people with “moderate” consumption were at similar risk for subarachnoid and intracerebral hemorrhage.
Comments: Doing the same studies over and over and getting the same result is not the same as finding the truth. The authors suggest that their study means the J-shaped curve is nuanced with some differences in associations for specific illnesses, but this study was no better at adjusting for confounders than many others. Non-drinkers and people with “moderate” consumption are so different (e.g., in this study 31% versus 16% were socioeconomically deprived, respectively) that adjustment is inadequate. Furthermore, medical record review might not have reliably identified former drinkers, which would in such cases contaminate the non-drinker group, causing them to appear to be sicker. Excluding younger people selects for those who survived drinking or became former (sick) drinkers (the same conceptual mistake made in the >30 studies finding benefit for hormone replacement). This study did not report on cancer, which is known to be associated with “moderate” drinking. Alcohol exposure was based on what clinicians jotted down when they asked, not a valid method. The J-shaped curve may or may not be a fallacy, but this study fails to tell us whether consumption of low amounts of a carcinogen (alcohol) is protective or not.
Richard Saitz, MD, MPH
Reference: Bell S, Daskalopoulou M, Rapsomaniki E, et al. Association between clinically recorded alcohol consumption and initial presentation of 12 cardiovascular diseases: population based cohort study using linked health records. BMJ. 2017;356:j909.