The scientific mapping of health and longevity variations in humans is largely a matter of mining demographic data for correlations, with little opportunity to directly determine causation over the decades needed for such studies. One particularly tightly-bound web of correlations involves intelligence, education, social status, wealth, and life expectancy. All influence one another, and a definitive determination of the root causes of these correlations remains a work in progress, and will probably continue to be so for some time yet.
Evidence for unexpected relationships exists, such as physical robustness being genetically linked to intelligence, as well as for the expected capacity of greater wealth to improve health and life expectancy. Analysis is certainly a complex business, and spirals out into many other possible correlations in behavior and circumstances. One of the better known lifestyle choices that touches on this area is moderate alcohol consumption, associated as it is with reduced mortality. It was always to some degree suspected that this association only exists because moderate drinking is in and of itself correlated with wealth and status, rather than being driven by any physical mechanism. One study to provide evidence in that direction is not enough on its own, of course, but it is something to take into account alongside others.
To assess whether a relationship between alcohol use and health exists for older adults before and after controlling for proxy and full indicators of socioeconomic status, we undertook a secondary analysis of data from 2,908 participants in the New Zealand Longitudinal Study of Ageing who completed measures of alcohol use, health, socioeconomic status proxies (income, education) and socioeconomic status itself. Sample mean age was 65, 52% were female, more than 80% were drinkers, and more than 75% had educational qualifications.
Moderate drinkers had better health and socioeconomic status than heavier or nondrinkers. The positive influence of moderate alcohol consumption on health was observed for men and women when controlling for socioeconomic status proxies, but was substantially reduced in women and completely disappeared for men when controlling for full socioeconomic status. socioeconomic status plays a key role in presumed "heath benefits" of moderate alcohol consumption for older adults. It accounts for any alcohol-health relationship in a sample of men of whom 45% consume at least one drink daily, and substantially attenuates the association between alcohol and health in a sample of women who are not frequent drinkers. Prior research may have missed the influence of socioeconomic status on this alcohol-health relationship due to the use of incomplete socioeconomic status measures.