MedicalResearch.com Interview with:
Dr. Jinhui Zhao PhD
Scientist, Centre for Addictions Research of BC
University of Victoria
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: There are now many studies questioning the validity of the theory that moderate alcohol consumption protects against heart disease. We provided an up to date and comprehensive review of the evidence from ‘cohort’ studies i.e. those that assess health risk behaviours of people then follow them up for a number of years to see what characteristics predict death from a particular condition. We wished to test the theory that the appearance of health benefits in relation to heart disease is due to biases that accumulate and become more severe when cohorts are recruited at older ages (e.g. over 55 years). We found evidence to support this hypothesis. Moderate drinkers recruited before 55 years of age did not show any evidence of reduced risk of heart disease even when followed up into old age. Moderate drinkers from the older cohorts, however, did appear to have significant benefits – a finding we attribute to selection biases that accumulate across the life-course.
Several published meta-analyses showed inconsistent findings about how alcohol consumption affects the risk of coronary heart disease (CHD). Most systematic reviews find associations between low-volume alcohol consumption and reduced CHD risk, while some also find increased CHD risk for higher levels of consumption (Maclure 1993, Corrao, Rubbiati et al. 2000, Corrao, Bagnardi et al. 2004, Ronksley, Brien et al. 2011, Roerecke and Rehm 2012). More recent evidence has accumulated to suggest that the case for cardio-protection may be less straightforward. The association of alcohol consumption with CHD may be confounded or modified by other factors such as age and sex and / or biased by those factors which have not been investigated or controlled for in these previously published studies.
MedicalResearch.com: What should readers take away from your report?
Response: We understand readers maybe tired of hearing contradictory news reports on this important question. We note we are not funded by any alcohol industry groups – this research was in fact largely funded by the US National Institutes of Health. We also based our analyses on all available published studies. We suggest our study is the latest and most comprehensive available. The main take home is that people should be skeptical as to whether there are health benefits from moderate alcohol use.
More background: Our study did not observe the association of reduced risk of mortality of CHD and moderate alcohol consumption in studies of those aged 55 years or younger at baseline, in high quality studies or in studies which controlled for heart conditions when the stratified analyses were conducted. The observed reduced risk of mortality from CHD with moderate alcohol consumption may be confounded by factors which have not been investigated or because of the misclassification of drinkers e.g. counting former drinkers as ‘abstainers’.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We present several recommendations for future research so that future investigations avoid some of the problems we have identified.
One is that drinking behavior should be assessed at multiple time points from young adulthood onwards and that drinking patterns that are stable over time are used in comparisons of health risks against those of lifetime abstainers.
We also suggest that
(i) ‘former drinkers’ are counted as drinkers, not abstainers and
(ii) that the level and duration of their drinking is carefully assessed. Over time we hoped that a less biased picture will emerge from this international literature and we can have more certainty as to the health consequences of alcohol in moderation.
We also recommend that future prospective studies not only avoid biased abstainer reference groups but also take steps to minimize other forms of selection bias across the life course, including that from competing disease risks; level of former drinking is considered and both former and current drinkers are combined when estimating the effects of all levels and patterns of alcohol consumption on health.
Corrao, G., V. Bagnardi, A. Zambon and C. La Vecchia (2004). “A meta-analysis of alcohol consumption and the risk of 15 diseases.” Prev Med 38: 613 – 619.
Corrao, G., L. Rubbiati, V. Bagnardi, A. Zambon and K. Poikolainen (2000). “Alcohol and coronary heart disease: a meta-analysis.” Addiction 95(10): 1505-1523.
Maclure, M. (1993). “Demonstration of Deductive Metaanalysis – Ethanol Intake and Risk of Myocardial-Infarction.” Epidemiologic Reviews 15(2): 328-351.
Roerecke, M. and J. Rehm (2012). “The cardioprotective association of average alcohol consumption and ischaemic heart disease: a systematic review and meta-analysis.” Addiction 107(7): 1246-1260.
Ronksley, P. E., S. E. Brien, B. J. Turner, K. J. Mukamal and W. A. Ghali (2011). “Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis.” British Medical Journal 342.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Journal of Studies on Alcohol and Drugs, 78(3), 375–386 (2017).
Jinhui Zhao, Ph.D., Tim Stockwell, Ph.D.,Audra Roemer, M.Sc., Timothy Naimi, M.D.,& Tanya Chikritzhs, Ph.D.
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