A systematic review 1 including 10 cohort studies (494,804 men and 54,832 women), 28 published RCTs (52,350 men), and two international studies (number of participants were not given) were abstracted in DARE.
Cohort studies: Relative risks in subgroup with lowest cholesterol concentration compared with the rest of the cohort were as follows: circulatory disease (not IHD) employed men 0.92; circulatory disease, community setting 1.12; cancer employed men 1.00, community setting 1.23 (significant); accidents & suicides employed men 0.95, community setting 1.29 (significant); other diseases employed men 1.08, community setting 1.62 (significant); all causes except IHD employed men 1.00, community setting 1.20 (significant).
Randomised controlled trials: Odds ratio for reduction in cholesterol concentration of 0.6 mmol/l: circulatory disease (not IHD) 1.00; cancer 1.07; accidents & suicides 1.17; other 1.07, all causes except IHD 1.07. The 95% CIs of these odds ratios all include 1. According to the randomised trials, the relative risk of death in treated/control groups per 0.6 mmol/l (10%) reduction in cholesterol was 1.06 (95% CI 0.97 to 1.17) in subjects without IHD, and 0.90 (95% CI 0.84 to 0.97) in subjects with IHD.
Comment: The quality of evidence is downgraded by inconsistency of results.
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