Data from a nationally representative sample of 5,404 community-dwelling Canadians ages 50 and older at baseline (1994/1995) was used to estimate the effects of alcohol drinking patterns on quality of life when subjects were aged =50 years and after a follow-up period. Health-related quality of life was assessed with the Health Utilities Index Mark 3 (HUI3). The authors report that most participants showed stable alcohol-consumption patterns over 6 years.
Detailed information was available on the participants alcohol consumption. Moderate drinkers were defined as those having 1 drinks per week with no more than 3 on any day for women and no more than 4 on any day for men. The repeated assessments allowed for the investigators to classify subjects according to changes over time in their drinking patterns, so that “persistent moderate drinkers” could be identified. 31.4% of the subjects decreased their intake over the follow-up period. The investigators also did secondary analyses among subjects who did not report any adverse health conditions (heart disease, cancer, stroke, or diabetes) during the first four years of follow up; these subjects were referred to as “consistently healthy.”
Regular moderate drinkers had the highest indices of quality of life at baseline, but subsequent changes in quality of life indicators were similar in all groups except for those reporting decreasing alcohol consumption. The investigators conclude that regular moderate drinkers had higher initial levels of health-related quality of life than abstainers and those in other groups. However, rates of decline over time were similar for all groups except those decreasing their consumption from moderate levels, who showed a greater decline in their level of health-related quality of life than regular moderate users.
While Forum reviewers admired the intent of this study, there were concerns about some of the statistical and epidemiologic aspects. The reasons that some people stopped drinking or decreased their intake were not known; although they were ‘consistently healthy’ at baseline. Forum reviewer Harvey Finkel comments: “As people age, even disregarding medical obstacles, social interactions generally decrease, which leads to both less stimulation to drink and less opportunity to drink.” It is thus important that the reasons that someone stops drinking, or decreases his or her intake, are taken into account.
Further, the “baseline” quality of life measures in this study were obtained when subjects were aged 50 or older; this baseline value of quality of life was higher in moderate drinkers. However, there are statistical problems if adjustments are made for this when quality of life is assessed subsequently and related to drinking pattern. Peto has described this problem as a “horse-racing effect.” He states that in prospective studies, the correlation between exposures (e.g., drinking pattern) and outcomes (e.g., quality of life) assessments during follow up are likely to be the same as the outcome at the end of follow up. As an analogy he uses a race between ‘slow’ and ‘fast’ horses; it is likely that the fast horses will be ahead at the mid-point of the race as well as at the end. Environmental effects on quality of life begin early in life, and if one adjusts for the mid-life value (as done and referred to as “baseline” in the present study), you may end up disregarding much of the effect of subsequent alcohol intake.
Overall, this study shows a positive relation between regular moderate alcohol intake and quality of life in middle-aged adults. The effects on the subsequent quality of life as one ages of continued alcohol consumption, or of decreasing intake, remain unclear.
