Low-Density Lipoprotein Cholesterol and the Risk of Cancer: A Mendelian Randomization Study
Marianne Benn, Anne Tybjærg-Hansen, Stefan Stender, Ruth Frikke-Schmidt, Børge G. Nordestgaard
Manuscript received August 19, 2010; revised December 15, 2010; accepted January 4, 2011.
Background: Low plasma levels of low-density lipoprotein (LDL) cholesterol are associated with an increased risk of cancer, but whether this association is causal is unclear.
Methods: We studied 10613 participants in the Copenhagen City Heart Study (CCHS) and 59566 participants in the Copenhagen General Population Study, 6816 of whom had developed cancer by May 2009. Individuals were genotyped for PCSK9 R46L (rs11591147), ABCG8 D19H (rs11887534), and APOE R112C (rs429358) and R158C (rs7412) polymorphisms, all of which are associated with lifelong reduced plasma LDL cholesterol levels. Plasma LDL cholesterol was calculated using the Friedewald equation in samples in which the triglyceride level was less than 354 mg/dL and measured directly by colorimetry for samples with higher triglyceride levels. Risk of cancer was estimated prospectively using Cox proportional hazards regression analyses and cross-sectionally by logistic regression analyses. Causality was studied using instrumental variable analysis. All statistical tests were two-sided.
Results: In the CCHS, compared with plasma LDL cholesterol levels greater than the 66th percentile (>158 mg/dL), those lower than the 10th percentile (<87 mg/dL) were associated with a 43% increase (95% confidence interval [CI] = 15% to 79% increase) in the risk of cancer. The polymorphisms were associated with up to a 38% reduction (95% CI = 36% to 41% reduction) in LDL cholesterol levels but not with increased risk of cancer. The causal odds ratio for cancer for a 50% reduction in plasma LDL cholesterol level due to all the genotypes in both studies combined was 0.96 (95% CI = 0.87 to 1.05), whereas the hazard ratio of cancer for a 50% reduction in plasma LDL cholesterol level in the CCHS was 1.10 (95% CI = 1.01 to 1.21) (P for causal odds ratio vs observed hazard ratio = .03).
Conclusion: Low plasma LDL cholesterol levels were robustly associated with an increased risk of cancer, but genetically decreased LDL cholesterol was not. This finding suggests that low LDL cholesterol levels per se do not cause cancer.
J Natl Cancer Inst 2011;103:508-519
http://jnci.oxfordjournals.org/content/103/6/508.full.pdf
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This study provides powerful evidence that low LDL does not cause cancer. And there is other evidence as well. Calorie restriction lowers serum cholesterol and reduces the risk of cancer and heart disease at the same time. Meta-analysis of statin trials show no increase in the overall risk of cancer even after 5 to 10 years of use. Countries with lower serum cholesterol like China have lower rates of prostate, breast and colon cancer than the U.S. Hunter gatherers with their low LDL levels are known for the near-absence of cancer. In clinical trials, the cholesterol lowering Ornish diet slows the growth of prostate cancer. And finally people with stable low cholesterol levels don't have higher cancer rates, just people whose cholesterol level has fallen recently. (1,2,3)
References
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2. Jacobs EJ, Newton CC, Thun MJ, Gapstur SM. Long-term use of cholesterol-lowering drugs and cancer incidence in a large United States cohort. Cancer Res. 2011 Mar 1;71(5):1763-71.
3. Frattaroli J, Weidner G, Dnistrian AM, Kemp C, Daubenmier JJ, Marlin RO, Crutchfield L, Yglecias L, Carroll PR, Ornish D. Clinical events in prostate cancer lifestyle trial: results from two years of follow-up. Urology. 2008 Dec;72(6):1319-23.
