Selection biases in observational studies affect associations between ‘moderate’ alcohol consumption and mortality

Abstract

Selection biases may lead to systematic overestimate of protective effects from 'moderate' alcohol consumption. Overall, most sources of selection bias favor low-volume drinkers in relation to non-drinkers. Studies that attempt to address these types of bias generally find attenuated or non-significant relationships between low-volume alcohol consumption and cardiovascular disease, which is the major source of possible protective effects on mortality from low-volume consumption. Furthermore, observed mortality effects among established low-volume consumers are of limited relevance to health-related decisions about whether to initiate consumption or to continue drinking purposefully into old age. Short of randomized trials with mortality end-points, there are a number of approaches that can minimize selection bias involving low-volume alcohol consumption.

Social and Behavioural Determinants of the Difference in Survival among Older Adults in Japan and England

“…Although we used comorbidities including hypertension in our models, having an objective blood pressure measure could have allowed further explanation of the differences in longevity between the two countries. In addition, because this study used cohorts of older adults who survived at least at the baseline of the survey, selection bias could overestimate the association of factors such as moderate alcohol drinking [27]. Our results suggest that moderate drinkers have a longer life than non-drinkers.…”

Consommation d’alcool et lignes directrices pour la consommation d’alcool à faible risque chez les adultes : une analyse transversale de l’Alberta’s Tomorrow Project

“…Les effets nocifs de la consommation d'alcool sur la santé pourraient être sous-estimés par rapport à ceux découlant du tabagisme : on a estimé qu'en 2000 l'alcool avait entraîné une charge mondiale de morbidité semblable à celle du taba gisme 8,48 . Les résultats récents en recherche ne montrent pas que la consommation d'alcool aurait des effets protecteurs sur l'organisme 18, [50][51][52] et certaines études antérieures ayant étayé l'existence d'« effets protecteurs » de la consommation d'alcool étaient défaillantes sur le plan méthodologique [53][54][55][56][57][58] -en fait, ce sujet demeure controversé 51,55,[59][60][61][62] . Une grande proportion de participants à l'étude ont indiqué consommer de l'alcool en quantité faible ou modérée (0,1 à 29,9 g d'éthanol par jour ou de moins de 1 verre par jour à 2 verres par jour) et pourraient ne pas être conscients des effets néfastes potentiels de quantités d'alcool dans l'organisme certes faibles mais régulières.…”

On bias in alcohol epidemiology and the search for the perfect study

“…In their paper in this issue, Naimi et al [1] highlight the possibility for selection bias in alcohol epidemiology, although the biases described are not limited to the field of alcohol research [2,3].…”

“…More than a decade ago it was almost taken for granted that moderate alcohol consumption conferred protective health effects, with those expressing scepticism grouped alongside 'doubters of manned lunar missions and members of the Flat Earth Society' [1]. Since then there has been a steady stream of studies that have set out to interrogate this association from multiple angles to determine the robustness of this claim [2][3][4].…”