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Drinking moderate amounts of alcohol may
not have the health benefits of long life that have been previously
asserted, due to flaws in research methods.
The latest findings should caution researchers
and the public to reconsider
the existing evidence and the popular notion that
moderate drinking is good for general health.
Several previous studies have demonstrated
that drinking moderate amounts of alcohol seems to reduce
mortality.
However, the authors point out that those
studies have a methodological flaw: they generally compare
drinkers with nondrinkers, but fail to distinguish between
those who never drank alcohol and those who quit drinking
for health reasons.
Lumping nondrinkers with ill health into
the group that abstains from alcohol entirely may produce
findings of an elevated mortality risk seemingly associated
with not drinking.
The investigators questioned more than
22,000 men aged 40 to 69 in northern Japan on their drinking
frequency in 1990, then tracked the men until 1997.
By separating the two groups of nondrinkers,
investigators found that ex-drinkers did have a higher risk
of mortality than nondrinkers and that moderate drinkers did
not actually have decreased mortality when compared with those
who had never been drinkers.
The result shows that, if an
inadequate comparison group (never drinkers combined
with ex-drinkers) is used, the protective effect of moderate
drinking is seriously exaggerated. Thus, moderate drinkers
spuriously showed a decreased risk when compared with nondrinkers,
which erroneously included both ex-drinkers and never drinkers.
However, the protective affect of moderate
drinking on reducing coronary heart disease has been well-established
and was also noted in the study. But because the rate of heart
disease in Japan is relatively low, this benefit has less
of an effect on reducing overall mortality than it might in
the United States, where heart disease is more prevalent.
JAMA
September 12, 2001;286:1177-1178
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