Variability in meta-analytic results concerning the value of cholesterol reduction in coronary heart disease: A meta-meta-analysis

Despite official support for the efficacy of cholesterol reduction, conside rable controversy exists, and meta-analyses of this topic have produced con flicting results. The authors assessed the variability of meta-analyses, ev aluating the cardiovascular value of cholesterol reduction while attempting to explain the variability. Meta-analyses were identified by electronic se arch and citation tracking. Included were those conducted prior to 1995 tha t dealt with cholesterol reduction and total mortality, cardiovascular mort ality, or nonfatal cardiovascular disease. In addition to extracting odds r atios for total mortality, cardiovascular mortality, and nonfatal cardiovas cular disease, the authors encoded methodological variables, publication va riables, and data concerning investigators' backgrounds. Twenty-three mete- analyses were reviewed, and 15 concluded that cholesterol reduction was ben eficial. Summary odds ratios for total mortality were heterogeneous, genera lly failing to support the value of cholesterol reduction. Odds ratios depe nded on inclusion criteria and investigator variables. Odds ratios for card iovascular mortality and for nonfatal cardiovascular disease were more homo geneous and supported the value of cholesterol reduction. Methodologically better meta-analyses tended to report more beneficial odds ratios. Although "supportiveness" of the value of cholesterol reduction was associated with inclusion/exclusion criteria and publication variables, the primary outcom e variable related to supportiveness was the statistical significance of th e odds ratios for cardiovascular mortality.