Cautions in Interpreting the Cardiovascular Effects of Moderate Drinking

Moderate
drinking has been linked to lower risks of cardiovascular
disease (CVD) and death. These potential benefits, however,
may be explained by more CVD risk factors in nondrinkers
(i.e., confounders). To explore this possibility, investigators
at the Centers for Disease Control studied 235,730 adult
nondrinkers* and moderate drinkers** who had participated
in a nationally representative telephone survey (54% response
rate).

• Most
  (27 of 30) characteristics associated with CVD were
  significantly more common in nondrinkers than in moderate
  drinkers.
  • Nondrinkers
    were older; less likely to be white, married, educated,
    and physically active; and less likely to have a
    high income, health insurance, a personal doctor,
    a flu shot, and cholesterol or colorectal cancer
    screenings.
  • They
    were also more likely to have diabetes, hypertension,
    obesity, high cholesterol, asthma, poor dental health,
    arthritis, and poor health status.
• Smoking
  and male sex were the only CVD risk factors more common
  in moderate drinkers.

Comments:

Many
epidemiological studies of moderate drinking have adjusted
for certain confounders but have either ignored others
(e.g., psychosocial risks) or not accounted for the interactions
between confounders (e.g., diabetes and lack of health
insurance). Although this study examined the prevalence
of possible confounders and found that most CVD risk factors
were more common in nondrinkers, it did not directly test
whether these confounders explained the relationship between
alcohol and CVD. A prominent alcohol epidemiologist recently
wrote that confounders may largely—or entirely—explain
the observed cardiovascular benefits of moderate drinking.
Only a large-scale, randomized trial can determine whether
alcohol decreases CVD. In the meantime, I agree with the
American Heart Association’s statement that “there is
little current justification to recommend alcohol as a
cardioprotective strategy.”

Richard Saitz, MD, MPH

Reference:

Naimi TS, Brown DW, Brewer RD. Cardiovascular risk factors and confounders among nondrinking and moderate drinking U.S. adults. Am J Prev Med. 2005;28(4):369-373.

Wannamethee SG. Alcohol and mortality: diminishing returns for benefits of alcohol. Int J Epidemiol. 2005;34(1):205-206.

Goldberg IJ, Mosca L, Piano MR. Wine and your heart: a science advisory for healthcare professionals from the Nutrition Committee, Council on Epidemiology and Prevention, and Council on Cardiovascular Nursing of the American Heart Association. Circulation. 2001;103(3):472-475.