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Cardiovascular risk factors and confounders among nondrinking and moderate-drinking U.S. adults

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Background

Studies suggest that moderate drinkers have lower cardiovascular disease (CVD) mortality than nondrinkers and heavy drinkers, but there have been no randomized trials on this topic. Although most observational studies control for major cardiac risk factors, CVD is independently associated with other factors that could explain the CVD benefits ascribed to moderate drinking.

Methods

Data from the 2003 Behavioral Risk Factor Surveillance System, a population-based telephone survey of U.S. adults, was used to assess the prevalence of CVD risk factors and potential confounders among moderate drinkers and nondrinkers. Moderate drinkers were defined as men who drank an average of two drinks per day or fewer, or women who drank one drink or fewer per day.

Results

After adjusting for age and gender, nondrinkers were more likely to have characteristics associated with increased CVD mortality in terms of demographic factors, social factors, behavioral factors, access to health care, and health-related conditions. Of the 30 CVD-associated factors or groups of factors that we assessed, 27 (90%) were significantly more prevalent among nondrinkers. Among factors with multiple categories (e.g., body weight), those in higher-risk groups were progressively more likely to be nondrinkers. Removing those with poor health status or a history of CVD did not affect the results.

Conclusions

These findings suggest that some or all of the apparent protective effect of moderate alcohol consumption on CVD may be due to residual or unmeasured confounding. Given their limitations, nonrandomized studies about the health effects of moderate drinking should be interpreted with caution, particularly since excessive alcohol consumption is a leading health hazard in the United States.

Introduction

When viewed prospectively, the initiation of alcohol consumption entails risk. In the U.S., about 30% of those who drink alcohol do so excessively, and excessive drinking is the third leading actual cause of death in the United States, killing 75,000 persons annually.1, 3, 4 Furthermore, even those drinking at “moderate” levels (as defined by their average daily consumption) are at increased risk of death from certain causes, including breast cancer. And finally, more than 20% of “moderate” drinkers in the U.S. general population report binge drinking (drinking 5+ drinks at one time), putting them at risk for injuries, violence, and other adverse health and social outcomes.4

While moderate drinkers in most, but not all, study populations appear to have a reduced risk of death from cardiovascular disease (CVD), unmeasured or residual confounding5, 6, 7, 8, 9, 10, 11, 12 could complicate the interpretation of these studies, especially since the strength of the association between moderate drinking and CVD outcomes is modest relative to other risk factors.13 It is important to clarify whether CVD benefits are being misattributed to moderate drinking, since initiating or increasing alcohol consumption also carries risk. The purpose of this study was to compare the prevalence of CVD risk factors and potential confounders among nondrinkers and moderate drinkers using data from the Behavioral Risk Factor Surveillance System survey (BRFSS). To date, there have been no randomized clinical trials examining the relationship between moderate alcohol consumption and any mortality endpoint.

Section snippets

Methods

The BRFSS is a population-based cross-sectional telephone health survey of U.S. adults aged ≥18 years conducted by state and territorial health departments with funding and technical assistance provided by the Centers for Disease Control and Prevention.14, 15 In 2003, there were 250,496 respondents, and the response rate was 54%. Average daily alcohol consumption was calculated by multiplying the number of drinks typically consumed by the fraction of days that alcohol was consumed (i.e., the

Results

Of the individual factors, 27 of 30 (90%) were significantly more prevalent among nondrinkers than moderate drinkers; only male gender and smoking were significantly more associated with moderate drinking. This was true before and after adjusting for age and gender. Examples of factors more commonly associated with nondrinking status included being older and nonwhite, being widowed or never married, having less education and income, lacking access to health care or preventive health services,

Discussion

The purpose of this population-based study was to assess the prevalence of known CVD risk factors and potential confounders among nondrinkers and moderate drinkers in order to determine if these factors could account for at least some of the apparent protective effect of moderate drinking on CVD. In sum, it appears that moderate drinkers have many social and lifestyle characteristics that favor their survival over non-drinkers, and few (if any) of these differences are likely due to alcohol

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