Essentially all observational cohort epidemiologic studies have shown a “J-shaped” curve for the association of moderate alcohol consumption with coronary heart disease and myocardial infarction, in that non-drinkers and heavy drinkers have higher risk than moderate drinkers. The present study presents a new approach for evaluating this relation by using electronic medical records for a very large number of patients (“big data”) in the UK to judge the relation between alcohol consumption and a variety of cardiovascular disease (CVD) outcomes. The study evaluated clinical data recorded by physicians from almost 2 million subjects, with about 115,000 CVD events recorded in public records. The exposures and outcomes came solely from the medical diagnoses given by individual physicians, and such diagnoses are known to often be inaccurate. For individual subjects, the exposure was based on codes for alcohol use or misuse in their medical records, and the cause of death was based on that recorded by the physician (which is not always consistent with diagnoses from autopsies or medical record reviews). Such problems would be expected to decrease the precision of the exposure and of outcome diagnoses.
Forum reviewers of this paper considered that the authors made a valiant effort in attempting to take into account the limiting factors of using big data for epidemiologic research. It is recognized that studies such as these cannot evaluate the pattern of drinking (regular versus binge) and the investigators were unable to evaluate different effects according to the type of beverage consumed (beer, wine, or spirits). It would be expected that both of these factors may have affected their results. Nevertheless, their conclusions strongly support the extensive observational data from cohort studies over many decades that have shown a higher risk among abstainers (versus moderate drinkers) for many CVD outcomes. In the present study, non-drinkers had significantly higher risk for unstable angina, myocardial infarction (MI), unheralded coronary death, heart failure, ischemic stroke, peripheral arterial disease, and abdominal aortic aneurysm. For most of these outcomes, heavy drinkers tended to have an increased risk (a J-shaped curve), but the risk for myocardial infarction and for stable angina remained decreased even for the heavy drinking category. For other manifestations of CVD, especially those related to cerebral artery disease (other than ischemic stroke), there was less of a clear pattern relating alcohol to disease. For their aggregate, overall outcome based on all manifestations of CVD, their analyses add further support for a J-shaped curve between alcohol intake and CVD.
Reference: Bell S, Daskalopoulou M, Rapsomaniki E, George J, Britton A, Bobak M, Casas JP, Dale CE, Denaxas S, Shah AD, Hemingway H. 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. http://dx.doi.org/10.1136/bmj.j909