International Scientific Forum on Alcohol Research Critique 157: A Mistaken Interpretation of Data Relating Alcohol to Mortality
By International Scientific Forum on Alcohol Research | 20 February 2015
The latest critique from The ISFAR has attacked recent research that was published in The BMJ
The authors of a recent paper on alcohol and mortality, and the case for age-specific alcohol consumption guidelines published in the BMJ, have carried out a regression analysis to examine the association of reported alcohol consumption with all-cause mortality, dividing their sample into different age groups. They used data from Health Survey for England 1998 to 2008, linked to national mortality registration data.
Their published results show lower risk of mortality (hazard ratios < 1.0 for mortality in comparison with recent non-drinkers and with never drinkers) for subjects in essentially all categories of moderate drinking.
All groups consuming less than 20 units a week experienced lower mortality rates than the life-long teetotalers. All the observed data is compatible with the kind of 15% to 20% protection suggested by hundreds of other papers over the last 30 year. Indeed, a graph of the authors' data indicates clearly the observed hazard ratio (relative risk of dying each year) – but was not published with the paper.
However, the authors have interpreted their analyses as indicating that moderate drinking is not associated with all-cause mortality for the vast majority of the population.
ISFAR forum members, and many other scientists, have been surprised by the conclusions of the authors, who apparently did not consider basic statistical principles (such as dealing with type-2 errors) in judging their results.
The investigators appear to have looked only at p-values and ignored the estimates of effect in their own data, coming to the conclusion that there is no association between moderate alcohol and total mortality for most age groups. Focusing only on significance testing for estimating effects has been strongly condemned by epidemiologists and statisticians and can lead to inaccurate results.
The paper reflects a gross misinterpretation of the data, which is not what would be expected in a publication in a leading journal. In other words, the authors’ conclusions are not backed up by their data.
A more appropriate headline based on this paper would be “Study supports a moderate protective effect of alcohol against all-cause mortality.” Given the wide media coverage of this article, with striking headlines indicating that moderate drinking does not affect mortality, one forum reviewer asked: “How can more than 30 years of research in this field be undone by one misguided paper in the BMJ? Once in a while I reflect on how some doctors and journalists interpret scientific papers; they seem to rely more on abstracts and press releases.”
The ISFAR forum considers that the conclusions of the authors of this paper are simply not supported by the data provided. Rather, their findings are in accordance with those from previous prospective studies showing that, for all age groups, moderate alcohol consumption is associated with a decrease in all-cause mortality risk.
To read the full critique, click here.
These critiques are published with the permission of The ISFAR.
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