International study questions health benefits of moderate drinking
The majority of studies suggesting that "moderate" drinking
helps prevent heart disease may be flawed, according to an international
In a new report, researchers from the U.S., Canada,
and Australia analyze 54 studies that linked how much people drink with
risk of premature death from all causes, including heart disease.
Researchers from the University of Victoria in British Columbia and the
University of California, San Francisco led the team.
The researchers investigated a suggestion put forth by
scientific skeptics of the ‘alcohol protects against heart attacks’
theory, that many of the studies conducted so far on drinking and
premature death made a consistent and serious error by including as
‘abstainers’ people who had actually cut down or quit drinking due to
declining health, frailty, medication use or disability. When such
studies show a higher death rate for abstainers than for moderate
drinkers, this result may reflect the poor health of some abstainers who
recently quit drinking rather than indicating a protective effect for
The team found just seven studies that included only long-term
nondrinkers in the ‘abstainers’ group. The results of these seven
studies showed no reduction in risk of death among the moderate drinkers
compared with abstainers. When the researchers combined the data from
these studies, they showed that it was possible to perform new analyses
that appeared to show a protective effect of moderate drinking – but
only when they deliberately included the error of combining long-term
abstainers with people who had cut down or quit drinking more recently.
The authors caution that their report has not disproved the
notion that light drinking is good for health, as too few error-free
studies have been performed. They suggest,however, that the extent to
which these benefits actually translate into longer life may have been
“The widely held belief that light or moderate drinking
protects against coronary heart disease has had great influence on
alcohol policy and clinical advice of doctors to their patients
throughout the world,” said Tim Stockwell, PhD, of the Centre for
Addictions Research at the University of Victoria. “These findings
suggest that caution should be exerted in recommending light drinking to
abstainers because of the possibility that this result may be more
apparent than real.”
“We know that older people who are light drinkers are usually
healthier than their non-drinking peers,” said Dr Kaye Fillmore of the
UCSF School of Nursing. “Our research suggests light drinking is a sign
of good health, not necessarily its cause. Many people reduce their
drinking as they get older for a variety of health reasons.”
The authors emphasize that there is a need for more
well-designed research in the future that assesses people’s alcohol
intake and abstinence more precisely as their drinking patterns change
The research that the team analyzed consisted of prospective
studies, including hundreds of thousands of individuals who were
followed over a number of years. Most studies were from North America
and Europe, some from the Caribbean and Asia. The majority of the
results were published in the 1980s and 1990s, with one study published
in 1974 and one as recently as 2004.
The team investigated this body of research using
meta-analysis – a method that synthesizes the results from many
different studies to determine if their results are in agreement,
statistically significant and the degree to which there is variation in
the results of the studies.
Light drinking was defined as having two drinks or fewer per
day (or about 30mls of pure alcohol per day) and drinking at least once a
month. Moderate drinking was 2 to 4 drinks per day. The effects of
other factors that influence health and life expectancy were controlled
as far as possible in analysis.
Two parallel analyses were carried out: one for 54 studies
evaluating death from all causes including heart disease and the other
for 35 studies evaluating heart disease deaths specifically. The two
analyses showed similar results. Moderate drinking was associated with
protection from premature death in the majority of studies – those
containing the ‘abstainer error. Protection was not found in the few
studies without the error, e.g. where moderate drinkers were compared
with long-term abstainers.
Previous meta-analyses that combined data from many studies
have shown that moderate drinking appeared to have a protective effect
against heart disease deaths and against premature death in general.
These studies did not address the effect of the ‘abstainer error.’ “By
ignoring this error, these meta-analyses perpetuated it,” Fillmore said.
“In this analysis, every attempt was made to test the
proposition of a health benefit more thoroughly than ever before in the
past,” Fillmore said. “Many other factors may account for the different
findings across studies. Fully 57 characteristics of these studies were
tested (e.g., smoking, health status, measurement characteristics).
None was found to challenge the finding that the ‘abstainer’ error was
responsible for alcohol's apparent protective effect.”
Stockwell noted that other diseases and conditions have been
found to have a protective effect as a result of the use of alcohol (in
contrast to abstaining from alcohol). “It is critical that future
research tests whether faulty measurement may have contributed to their
findings,” he said. “Also, it is well to remember that the types of
research usually used to find links between lifestyle factors (e.g.
diet, exercise, medication use, in addition to alcohol use) and disease
later in life have a high potential for error and on their own cannot
The authors credit British researcher Professor Gerry Shaper
of the Royal Free and University College Medical School in London,
England, for first proposing the possibility of an ‘abstainer error’
in the design of prospective studies of the association between alcohol
use and heart disease risks. The newstudy supports Professor
Shaper’s conclusion that while the known biological effects of alcohol on
risk factors for coronary heart disease are of scientific interest, they
have very limited significance for public health.
“This study was performed in the spirit of the tradition that
all scientific findings are open to challenge,” Fillmore said.
“Competing hypotheses, even if unpopular, should be encouraged and
tested to be sure that accepted beliefs about health are sound.”
Moderate alcohol use and reduced mortality risk: Systematic
error in prospective studies Kaye Middleton Fillmore, William C. Kerr,
Tim Stockwell, Tanya Chikritzhs, and Alan Bostrom
Addiction Research and Theory 2006.