SERUM-CHOLESTEROL AND MORTALITY-RATES IN A NATIVE-AMERICAN POPULATIONWITH LOW-CHOLESTEROL CONCENTRATIONS - A U-SHAPED ASSOCIATION

Background Low serum cholesterol concentrations are associated with hi gh death rates from cancer, trauma, and infectious diseases, but the m eaning of these associations remains controversial. The present report evaluates whether low cholesterol is likely to be a causal factor for mortality from all causes or from specific causes. Methods and Result s Among 4553 Pima Indians greater than or equal to 20 pears old, a pop ulation with low serum cholesterol (median, 4.50 mmol/L), 1077 deaths occurred during a mean follow-up of 12.8 years. Trauma was the most co mmon cause. The relationship between serum cholesterol measured at 2-y ear intervals and age-and sex-standardized mortality rates was U-shape d. Cholesterol was related positively to mortality from cardiovascular diseases and diabetes (including nephropathy) and negatively to morta lity from cancer and alcohol-related diseases. The relationship was U- shaped for mortality from infectious diseases, and cholesterol was not related to mortality from trauma. Change in cholesterol from one exam ination to the next was positively related to mortality from diabetes. In proportional-hazards models adjusted for potential confounders, th e relationship between baseline cholesterol and mortality was U-shaped for all causes and diabetes and positive for cardiovascular diseases. Other relationships were nonsignificant. Among 3358 subjects followed greater than or equal to 5 years, the relationship was significant an d positive only for mortality from cardiovascular diseases. Conclusion s Despite a high exposure risk for Pima Indians, If low cholesterol le vel is a causal factor, the relationships between low serum cholestero l and high mortality rates probably result from diseases lowering chol esterol rather than from a low cholesterol causing the diseases.