We all know the risks of high cholesterol. Low cholesterol can also be unhealthy, according to a recent report from Japan. Their study of 12,334 healthy adults ages 40 to 69 years showed that individuals with cholesterol numbers in the lowest group had significantly higher mortality from all causes, and from cancer in particular.
As background for this study, the authors noted that use of statin drugs for high cholesterol is associated with increased rates of breast cancer, cancer incidence in elderly people, and total cancer incidence. Increased overall mortality rates have been reported for individuals with low cholesterol, but one analysis suggested this was due to liver disease alone. Reference 1 includes a detailed analysis of the cause of death in their large sample, with a total of 145,312 person-years included.
The cholesterol numbers were divided into the following groups:
1. Low, less than 4.14 mmol/L. This corresponds to less than160 mg/dL in U.S. units.
2. Normal, 4.14 to 5.17 mmol/L, corresponding to 160 to 200 mg/dL.
3. Elevated, 5.17 to 6.21 mmol/L, corresponding to 200 to 240 mg/dL.
4. High, above 6.21 mmol/L, corresponding to more than 240 mg/dL.
The statistical analysis showed that women in the low cholesterol group had 1.24 deaths for every one death in the normal cholesterol group, when the data were adjusted for age, systolic blood pressure, HDL cholesterol, smoking, drinking, and body mass index. Excluding deaths due to liver disease produced only a small change in the results. Excluding subjects with a history of cancer, stroke, or heart attack (myocardial infarction) produced an even stronger effect: the low cholesterol group had 1.29 deaths for every one death in the normal cholesterol group. Data for men were similar.
When the data were broken down by cause of death, the authors found women in the low cholesterol group had 1.44 times the cancer mortality rate of those in the normal cholesterol group. Mortality rates from stroke and heart disease were similarly elevated for low cholesterol participants.
The authors suggested additional cancer screening for individuals with low cholesterol.