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Alternative explanations for the protective effect of moderate
alcohol intake, relying on ever more tenuous confounding effects,
have been discredited one by one. The apparently protective effect of
moderate alcohol consumption has so far survived the use of controls
for sociodemographic status,3 for the "sick quitter
hypothesis"4 (ie, the suggestion that
many abstainers have stopped drinking because of serious illness),
for the amount of cholesterol in the diet,5 and even for the degree of
social isolation.6 As evidenced in the study by
Simons et al,2 the protective effect is
fairly specific to cardiovascular disease and does not operate for
other major causes of death in older people such as cancer. While a
handful of recent studies have failed to find a protective effect for
moderate drinking,7,8 these are still heavily
outnumbered by those with positive findings.1 In fact, the range of
different countries and cultures in which the phenomenon has been
documented is also testimony to its robustness, even if different
levels of consumption appear to provide the benefit in different
drinking cultures.1
So, does medical science need further research on this topic? My
contention is that, while the basic protective properties of
moderate alcohol consumption appear to have been identified, the
precision of the measurement of drinking levels and patterns in these
studies needs to be sharpened if we are to have a firmer basis for
advising people how to drink to avoid ill-health. The recent major
systematic review commissioned by the National Health and Medical
Research Council to underpin revisions to Australia's national
guidelines on low risk drinking found that nearly all
epidemiological studies in this area only attempt to measure one of
the important dimensions of alcohol consumption: total volume of
drinking, usually expressed as average intake per day.1
Despite recent evidence that pattern of drinking plays a role
independent of volume,9 large-scale
epidemiological studies rarely include simple items in their
questionnaires tapping this dimension, such as frequency of
drinking five or more drinks in one day, or maximum amount consumed on
one day. Simons et al make a rare contribution to our knowledge by
providing an analysis of mortality risk, based not only on average
volume of alcohol across all days, but also on usual
amount consumed on a drinking day. Clearly, these can be very
different measures (eg, seven drinks in a day once a week versus one
drink every day of the week).2 While the power of the
analyses in Simons et al is limited by sample size, usual consumption
of five or more drinks for men and of three or four drinks in a day for
women was not associated with a significantly reduced risk of
death.2
It should be noted, however, that questions regarding "usual"
consumption tend to suffer from a bias towards low-consumption
occasions and against less frequent occasions of high
intake.10 Forthcoming World Health
Organization guidelines on measurement of alcohol consumption
advise that a superior method is the "graduated quantity frequency",
in which respondents are asked how often they drink at each of
different levels of consumption, starting with the highest (eg, "How
often do you drink 20 drinks on one day?").10 The same guidelines
identify another problem bedevilling attempts to convert the
results of alcohol studies into precise advice for drinkers:
assumptions about the alcohol content of drinks reported vary
between studies and are usually not empirically based. A number of
studies from different countries have attempted to document
usual-serve sizes employed by random samples of drinkers and found
these to vary significantly from those usually assumed by
researchers.11,12 One study found that
the bias created towards under-reporting of consumption was massive
in one particular population subgroup: Afro-American
women.13
One striking consequence of a failure to measure pattern of alcohol
consumption adequately can be the false identification of special
benefits from one type of alcoholic beverage over another. Wine is
often reported as being most associated with benefits, but being a
wine drinker as opposed to a beer and spirits drinker is a marker for
many other things, including a tendency towards a more consistent
pattern of daily drinking rather than occasional
"bingeing".14 A well known Danish
study,3 often cited as evidence for a
greater benefit of wine over other drinks, measured alcohol
consumption by only asking about how much people usually drank if
they drank every day. Because this is a less frequent pattern for
heavy drinkers of beer and spirits, many of the latter will have been
falsely categorised as light or moderate drinkers, thus
significantly biasing against finding protective effects for these
beverages.
The two fields of epidemiology and alcohol studies have much to learn
from each other. If epidemiological studies of risk factors for heart
disease do not improve their measurement of patterns and levels of
alcohol use, it will remain very hard to give precise advice to
drinkers who wish to minimise harms and maximise benefits of alcohol
consumption. In reality, despite hundreds of studies into the
protective effects of alcohol in relation to heart disease, research
into this area has only just begun.
Timothy R Stockwell
Director
National Centre for Research into the Prevention of Drug Abuse
Curtin
University of Technology, Perth, WA
- Single E, Ashley MJ, Bondy S, et al. Evidence regarding the level of
alcohol consumption considered to be low-risk for men and women.
Final report. Canberra: National Health and Medical Research
Council, 2000. URL:
<http://www.nhmrc.health.gov.au/advice/alc-comp.htm>
(accessed 29 June 2000).
-
Simons LA, McCallumJ, Friedlander Y, et al. Moderate alcohol
intake is associated with survival in the elderly: the Dubbo Study.
Med J Aust 2000; 173: 121-124.
-
Gronbaek M, Deis A, Sorensen TIA, et al. Mortality associated with
moderate intakes of wine, beer or spirits. BMJ 1995; 310:
1165-1169.
-
Rehm J, Sempos CT. Alcohol consumption and all-cause mortality:
questions about causality, confounding and methodology.
Addiction 1995; 90: 493-498.
-
Rehm J, Sempos CT. Alcohol consumption and all-cause mortality.
Addiction 1995; 90: 471-480.
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Murray RP, Rehm J, Shaten J, Connett JE. Does social integration
confound the relation between alcohol consumption and mortality in
the Multiple Risk Factor Intervention Trial (MRFIT)? J Stud
Alcohol 1999; 60: 740-745.
-
Leino EV, Romelsjo A, Shoemaker C, et al. Alcohol consumption and
mortality. II. Studies of male populations. Addiction 1998;
93: 205-218.
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Hart CL, Smith GD, Hole DJ, Hawthorne VM. Alcohol consumption and
mortality from all causes, coronary heart disease, and stroke:
results from a prospective cohort study of Scottish men with 21 years
follow up. BMJ 1999; 318: 1725-1729.
-
Rehm J, Ashley KJ, Room R, et al. On the emerging paradigm of drinking
patterns and their social and health consequences.
Addiction 1996; 91: 1615-1621.
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World Health Organization (Substance Abuse Department).
International guidelines for monitoring alcohol consumption and
harm. Geneva: WHO. In press.
-
Stockwell T. Information provided in Australia about the size of
"standard drinks". Med J Aust 1992; 156, 295.
-
Lemmens P. The alcohol content of self-report "standard drinks".
Addiction 1994; 89: 593-602.
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Kaskutas L, Graves K. An alternative to standard drinks as a
measure of alcohol consumption. Paper presented at International
Conference on the Measurement of Drinking Patterns, Alcohol
Problems and the Connection; 2000 April 2-7; University of
Stockholm, Sweden. In press.
-
Doll R. One for the heart. BMJ 1997; 315: 1664-1668.
©MJA 2000
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