It has long been recognized from epidemiologic studies that both the positive and negative health effects of alcohol consumption are modified by the socio-economic status (SES) of individuals. Higher SES subjects (higher education, income, job status, etc.) are more likely to be regular moderate drinkers, while lower SES subjects are more likely to binge drink and under-report their alcohol intake. Truly moderate drinkers tend to have better health outcomes and fewer adverse effects from alcohol, and consistently show lower total mortality risks than non-drinkers or heavy drinkers.
The present study, from the New Zealand Longitudinal Study of Ageing, used data from the second examination of the cohort to do a cross-sectional analysis judging the relation of alcohol consumption to “health”. When controlling for age, income, and education (the latter two as measures of SES), they found a significant “J-shaped” association between reported alcohol intake and self-reported “physical health”. However, the authors state that they then used another measure of SES, the Living Standard Index-Short Forum (ELSI-SF), and found that the reported alcohol intake of subjects correlated with their measure of physical health almost exactly the same as with the results of the ELSI-SF. They conclude that there are no health benefits of moderate drinking, only that people with higher SES are more likely to drink moderately.
Forum members considered it unfortunate that the assessment of the exposure (alcohol intake) used in this study was based only on self-reported average intake and did not include data on the pattern of drinking (binge versus regular moderate intake, etc.). Further, their outcome was based only on a self-reported questionnaire of “physical health,” and did include any hard data; an overall index based on assessments of functional status, biomarkers of and the occurrence of disease, and mortality would be preferable when judging “health benefits” of alcohol. The Forum considered that the authors used inadequate indices of both the exposure to alcohol and their assessment of “health” (based on a questionnaire) to reach a conclusion that moderate drinking does not have any beneficial effects on health. This was done ignoring the massive amount of not only observational data but results from extensive experimental studies over more than four decades. Such research has found that moderate drinking not only has beneficial effects on assessments of physical health and disease occurrence, but results in significantly lower total mortality when moderate drinkers are compared with abstainers.
Regardless, given that this study, as have almost all epidemiologic studies, has shown the importance of SES on health outcomes, a key challenge to scientists is to seek to determine the mechanisms by which these differences occur. One potentially important factor is that the differing health outcomes relate to errors in judging the exposure, i.e., inadequate assessments of alcohol: not evaluating for binge drinking versus regular intake, consuming alcohol with or without food, type of beverage consumed, under-reporting of intake, etc. Also, much broader definitions of “health” are needed (rather than the results of a single self-administered questionnaire) that include the effects on functional status, disease states, and mortality. And, it is important that other lifestyle factors (smoking, drug use, etc.) that affect health be properly evaluated as determinants of health. Only with such data will we be able to fully judge the overall effects of alcohol consumption on health outcomes.
Reference: Towers A, Philipp M, Dulin P, Allen J. The “Health Benefits” of Moderate Drinking in Older Adults may be Better Explained by Socioeconomic Status. Pre-publication: J Gerontol B Psychol Sci Soc Sci 2016. doi:10.1093/geronb/gbw152 For the full critique of this paper by members of the International Scientific Forum on Alcohol Research, please click here.