How stable is the risk curve between alcohol and all-cause mortality and what factors influence the shape? A precision-weighted hierarchical meta-analysis

Objective: To determine the influence of six determining variables on the shape of the risk curve between alcohol and all-cause mortality. Methods: Data: Based on a systematic search with clear inclusion criteria, all articles on alcohol and all-cause mortality until 2000 were included. Statistical methods: Precision-weighted pooling of relative risks (RRs); precision-weighted hierarchical analysis. Variables: For pooling: RRs for different categories of average volume of drinking, lifetime abstainers and ex-drinkers. For hierarchical analysis: on first level: consumption in grams of pure alcohol per day; on second level: length of follow-up time in months; per capita consumption; average age, proportion of abstainers, average volume of drinking, and variability of average volume of drinking at baseline. Outcomes measures: RR of former and current drinkers for all-cause mortality compared to abstainers. Results: The main hypotheses could be confirmed for males: Ex-drinkers had a higher mortality risk than lifetime abstainers; the higher and the more diverse the average volume of alcohol consumption, the wider the dip of the curve; the older the persons at baseline, the more pronounced the protective effect; and the longer the follow-up time, the less pronounced the protective effect. Except for average volume of drinking effects for females went in the same direction but with one exception did not reach significance. Conclusions: There are systematic influences on the shape of the risk curve between alcohol and all-cause mortality. The overall beneficial effect of light to moderate drinking remained under all scenarios, indicating a high validity of the overall shape despite the heterogeneity between studies.