Systematic differences among never, occasional and moderate alcohol users in southern China, and its use in alcohol research: a cross-sectional study.

BACKGROUND: Western observational studies show moderate alcohol use, compared with never use, positively associated with health. Moderate users differ systematically from others, making these observations vulnerable to confounding. Observations from other contexts may help distinguish whether these associations are confounded. To assess whether southern Chinese would provide a more suitable setting to examine the association of moderate alcohol use with health, we compared never alcohol users with moderate alcohol users and occasional users in this setting.
METHODS: We used age-adjusted multinomial regression to assess sex-stratified associations of alcohol use (never, occasional (<1 occasion/week), moderate (≤140 g ethanol/week for women and ≤210 g for men)) with health attributes and indicators in the Guangzhou Biobank Cohort Study (2003-2008) (n=26 361).
RESULTS: Among men, moderate alcohol users, when compared with never users, had slightly lower socioeconomic position and unhealthier lifestyle. Conversely, occasional alcohol users, when compared with never users, had higher socioeconomic position and healthier lifestyle. Among women, when compared with never users, both occasional and moderate users had higher socioeconomic position and healthier lifestyle. However, all alcohol users for both sexes, when compared with never users, were more likely to be ever smokers and to be exposed to secondhand smoke.
CONCLUSIONS: Observations in alcohol epidemiology may be affected by confounding due to contextually specific systematic differences. Results from a particular setting should not be interpreted as causal unless they are verified in different populations and, preferably, in non-observational studies.