Objective: Reducing serum cholesterol lowers the risk for ischemic heart disease, but its effects on other vascular diseases are unknown. Published trials were reviewed to determine the effect of cholesterol-lowering interventions on fatal and nonfatal stroke.
Design: Meta-analysis of randomized, controlled trials.
Data identification: A literature search of English-language studies examining the effect of modified diets or medications on cardiovascular end points from 1965 to 1992 using MEDLINE and a review of references of five quantitative overviews of cholesterol reduction and coronary disease.
Data analysis: Thirteen studies met three eligibility criteria: patients randomized to intervention or control; fatal or nonfatal stroke reported separately; and end points assessed without knowledge of treatment status. Heterogeneity among studies and overall effects of treatment on fatal and nonfatal stroke were estimated using the Mantel-Haenszel-Peto method to combine independent study results. The influence of various study designs and interventions was explored using subgroup comparisons.
Results: For fatal stroke, the overall odds ratio associated with cholesterol-lowering interventions in 13 trials was 1.32 (95% Cl, 0.94 to 1.86), and the odds ratio for the 10 single-intervention trials was 1.34 (Cl, 0.91 to 1.96). Among eight trials reporting nonfatal events, the summary odds ratio for nonfatal stroke for treated participants compared with controls was 0.88 (Cl, 0.70 to 1.11), and the odds ratio for total strokes was 0.98 (Cl, 0.80 to 1.19). Among three trials using clofibrate, treatment significantly increased the risk for fatal stroke (odds ratio, 2.64; Cl, 1.42 to 4.92) but not for nonfatal stroke (odds ratio, 0.87; Cl, 0.61 to 1.26). Regression analysis showed no statistical association between the magnitude of cholesterol reduction and the risk for fatal stroke.
Conclusions: Lowering serum cholesterol through modified diets or medications does not reduce stroke mortality or morbidity in middle-aged men. Clofibrate appears to increase the risk for fatal strokes, but the mechanism for this effect is unknown.