| Abstract: | Background: Attention has been focused on the increased risk of high cholesterol, but the effect of low cholesterol remains unclear and receives little attention. Method: The study cohort, 537,430 adults in Taiwan who went through a medical screening program between 1996 and 2008, was followed up for an average of 8.5 years for mortality and cancer incidence, with 18,745 deaths and 17,714 cancer cases identified. Low and very low cholesterol or LDL were defined as < 180 and <160, or <110 and <90 mg/dL, respectively. Cox proportionate model was used for hazard ratio (HR) calculation, by controlling for all relevant risk factors (Age, gender, BMI, smoking, drinking, blood pressure, blood sugar, physical activity and anemia) Results: One out of four (24.6%) had low cholesterol and 7.5% had very low cholesterol, in contrast to 10.4% with high cholesterol. Increases in all cancer mortality were found for those with low cholesterol (HR:1.41, with 95% 1.3-1.5) and very low cholesterol (HR: 1.58 with 95% 1.4-1.7), with 180-239 mg/dL as reference. Similar results were seen for cancer incidence. The increase came prominently from liver cancer (HR:2.86), and the increases remained after all deaths or all cancer incidences within the first 3 years were excluded (HR: 1.31), or after HBV carriers were excluded (HR: 1.33). All cancer mortality increased by 1% for every unit decrease of cholesterol across all levels. With 60% increase in all-cause mortality, the life span of very low cholesterol was shortened by 5-6 years. Conclusion: Found in 1/4 of adult Asians, subjects with low cholesterol (<180 mg/dL), a level commonly reached by those taking statins or on vegetarian diet, had approximately 50% increase in cancer risks. The inverse relationship existed across all levels of cholesterol, with 10% increase for every 10-unit decrease. Those with very low cholesterol had their life span shortened by 5-6 years. While reverse causation with pre-clinical cancer cases could be responsible, the fact that the cancer risks remained after excluding first three years of cancer implied low cholesterol is an independent risk factor or risk marker for all cancer. In this Asian community, low cholesterol should receive as much attention as high cholesterol. |
