There is a lot of evidence in the literature that claims moderate alcohol consumption is associated with reduced mortality in adults. For example, studies have shown that wine consumption in particular reduces cardiac mortality, as well as other beneficial effects. One hypothesis is that because wine has such unique protective properties, it is this beverage that provides the reduced mortality in adults, and not all types of alcoholic beverages. Though many studies have shown these types of results, many are still concerned that these results are too tightly linked with several confounding factors, including socioeconomic and lifestyle factors.
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Preferences for wine has been shown to be highly associated with a higher socioeconomic status, a healthier lifestyle, and better health statuses in general. One study controlling for many of these factors found that associations between reduced mortality rates and reduced risk of heart attack in older adults were not correlated with the type of alcohol that was consumed.
So, does wine consumption really reduce mortality in adults? Or are the results of many of the studies out there inaccurate due to uncontrolled confounding factors?
The goal of the study presented today was to answer these very questions. What is the relationship between the level of wine consumption and the mortality rate in adults when controlling for confounding factors? Several questions were asked in this study: 1) Is the mortality advantage of moderate alcohol consumption retained in both high-wine consumption individuals and low-wine consumption individuals?; 2) Are there significant confounding factors associated with a high level of wine consumption?; 3) Are controlling for confounding factors, is there a mortality advantage of high-wine consumption versus low-wine consumption?; and finally 4) Is there a mortality advantage associated with the level of wine consumption independent of the confounding factors?
Methods
This study was a part of a larger study examining late-life patterns of alcohol consumption and drinking problems, and stress and coping processes among late-middle aged adults. At baseline, participants were between 55 and 65 years old and who had outpatient contact with a health care facility within the last 3 years. Lifetime nondrinkers were excluded from the study. All data were collected by self-reporting.
802 adults participated in the study, and were broken down into three different groups: abstainers, high-wine consumption moderate drinkers, and low-wine consumption moderate drinkers. Information was collected on alcohol consumption, sociodemographic factors, health behaviors, health problems, and physical activity.
The following factors were assessed for alcohol consumption: average daily ethanol consumption, quantity of alcohol consumed, frequency of alcohol consumed, and type of alcohol consumed. From the information gathered, quantity-frequency values were calculated in order to create participant indices of average daily ethanol consumption for each beverage type. By summing this average daily ethanol consumption index for each beverage type, a composite index of the participants’ overall average daily ethanol consumption was calculated.
Abstainers were identified as those who had consumed no alcohol in the past year. Moderate drinkers were identified as those who consumed from one to less than three drinks per day in the last month. There were a total of 345 abstainers and 560 moderate drinkers in total.
Among the moderate drinkers, the level of wine consumption was determined. Low-wine consumers were the moderate drinkers who consumed less than or equal to one third of their daily ethanol consumption from wine. High-wine consumers were the moderate drinkers who consumed two thirds or more of their daily ethanol consumption from wine. There were a total of 281 low-wine consumers and 176 high-wine consumers.
Sociodemographic factors measured were: age, gender, socioeconomic status, total annual family income, years of education, and marital status.
Health problems measured as a choice of 9 different problems (participants could select as few or as many that applied to them) that were physician-diagnosed medical conditions within the past year including: cancer, diabetes, heart problems, stroke, high blood pressure, anemia, bronchitis, kidney problems, and ulcers. Participants were also asked to choose from 7 different physical problems that were applicable to them within the last year, including: pain in the heart or tightness/heaviness in the chest, trouble breathing or shortness of breath, constant coughing or frequent heavy chest colds, frequent cramps in the leg, swollen ankles, getting very tired in a short time, and trouble climbing stairs or getting outdoors.
The following health behaviors were measured: tobacco smoking and physical activity. For physical activity, participants were asked to choose their level of activity based on four scenarios: swimming or tennis with friends, swimming or tennis with family, long hikes or walks with friends, or long hikes or walks with family.
The outcome variable for this study was death. At the end of the 20-year follow-up for this study, 435 participants out of 802 had died.
Results
- Not taking any confounding factors into consideration, the mortality rate was highest for abstainers (69%), intermediate among low-wine consumers (50%), and lowest for the high-wine consumers (32%).
- After controlling for the covariates (a.k.a. confounding factors described above), both high-wine and low-wine consumption moderate drinkers showed reduced mortality risks compared with abstainers.
What about the level of wine consumption?
- Level of wine consumption was significantly associated with 5 out of 6 covariates, and trending with the 6th, physical activity.
- Compared to high-wine consumers, low-wine consumers tended to be older, male, more reported health problems, tobacco smokers, lower on the socioeconomic scale, and reported in engaging in less physical activity.
Is there a mortality advantage associated with level of wine consumption among moderate drinkers?
- WITHOUT controlling for demographic and lifestyle confounding factors, but controlling for average daily ethanol consumption, low wine consumption among moderate drinkers was associated with a higher risk of mortality (85%) compared to high wine consumption.
- Mortality risk did not differ between men and women.
What about the mortality advantage associated with level of wine consumption among moderate drinkers after controlling for all confounding factors?
- After controlling for all of the covariates, including average daily ethanol consumption, the initial difference in mortality between high-wine consumers and low-wine consumers was no longer significant.
- Mortality risk did not differ between men and women, even after controlling for all confounding factors.
Conclusions
After controlling for confounding factors, which is frequently not done in related studies, the results of this study found that the mortality advantage of moderate alcohol consumers over those abstaining from alcohol does not appear to be based solely on their consumption of wine. In other words, there is no difference in mortality rate between wine drinkers and other alcoholic beverage drinkers when controlling for all confounding factors.
The study found that there is strong evidence that confounding sociodemographic, behavioral, and health factors were highly associated with wine consumption. In other words, a lower mortality rate for wine drinkers doesn’t necessarily mean it’s because of the wine they are consuming, but could be instead due to one or many of the sociodemographic, health, and other factors that are highly correlated with wine consumption.
The authors of this study did address some limitations to their methods, which I will briefly summarize here. First of all, these results are not from experimental findings and do not show evidence of causality. Second, these results are based off self-reports, which may or may not be completely accurate (though many studies have shown that they are). Third, the measure of physical activity was extremely limited and therefore the results reported may not be accurate to what physical activity was actually performed in real life for each participant.
Next, the study did not differentiate between red and white wine, though in one study, it was shown that mortality risk was identical between red and white wine. Next, the study did not give any information on patterns of hazardous drinking (i.e. binge drinking) if they occurred in the life of the participant. Next, the majority of the participants were white, so these results may not be generalizable to the general public. Finally, the study did not take into consideration any changes in alcohol consumption patterns over the 20 year period.
Overall, this study found that the failure of many studies to control for confounding factors, such as sociodemographics and health behaviors, has led to the widely accepted notion that there is a mortality advantage for older adults who consume wine instead of other alcoholic beverages. However, what this study found is that many sociodemographic, behavioral, and health status are linked to both the level of wine consumption and to increased mortality, therefore the results of other studies not controlling for these variables are inaccurate. So, after controlling for all of these confounding factors, the benefit of lower mortality associated with moderate wine consumption is eliminated. Note: wine consumption DOES lower mortality risk compared to those that abstain from alcohol all together, but this study shows that it's nothing special about wine that's lower that risk, but perhaps the ethanol itself.
I’d love to hear what you all think of the results and implications of this study! Please feel free to comment below (no html tags, please).
Source: Holahan, C.J., Schutte, K.K., Brennan, P.L., North, R.J., Holahan, C.K., Moos, B.S., and Moos, R.H. 2012. Wine Consumption and 20-Year Mortality Among Late-Life Moderate Drinkers. Journal of Studies on Alcohol and Drugs 73(1): 80-88.
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
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