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Evidence summaries

Hazards of Reducing Serum Cholesterol

Low or reduced serum cholesterol concentration does not appear to significantly increase mortality from any cause other than haemorrhagic stroke. This risk affects only people with a very low concentration and even in these the risk is outweighed by the benefits from the low risk of ischaemic heart disease at least in patients with ischaemic heart disease. Level of evidence: "B"

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.

    References

    • Law MR, Thompson SG, Wald NJ. Assessing possible hazards of reducing serum cholesterol. BMJ 1994 Feb 5;308(6925):373-9. [PubMed][DARE]

Primary/Secondary Keywords