Excessively low levels of low-density lipoprotein (LDL) cholesterol and triglycerides are associated with a higher all-cause mortality among American Indians, according to a new study published online ahead of print
in Journal of Diabetes and Its Complications
While it is accepted that low LDL cholesterol is associated with lower mortality among whites, the same cannot be said for all populations, the authors explained. They sought to examine the effects of cholesterol and triglycerides on mortality in the American Indian population.
Beginning in 1993, triglyceride and high-density lipoprotein (HDL) cholesterol levels were reported among American Indians in the Southwest who were age 40 years or older. Patients included in the study were examined at least once between 1993 and 2007 and were followed from that first examination, considered the baseline, until death or December 31, 2011.
The researchers analyzed the effects of LDL, non-HDL, and HDL cholesterol; triglycerides; and the triglyceride:HDL cholesterol ratio on mortality. The found that, in general, lower concentrations of these serum lipids and higher levels of HDL cholesterol were “associated with increased all-cause mortality and mortality from all natural causes, liver disease, and external causes.” Meanwhile, high levels of serum lipids were associated with a greater cardiovascular mortality.
The authors hypothesized that alcohol consumption was one possible explanation for the negative associations between LDL cholesterol, non-HDL cholesterol, and triglycerides and mortality.
“American Indians are reported to have lower rates of alcohol use but higher rates of binge drinking among users than reported in national US surveys,” the authors wrote. Alcohol consumption influences lipid concentration and levels of serum cholesterol and triglycerides are reduced in patients with liver disease.
While the relatively long follow-up of this study was one strength, the authors’ inability to control for potential confounders, such as low socioeconomic status and baseline liver function, and the inability to identify underlying causes of liver disease were main limitations.
“Low cholesterol and low triglycerides are widely believed to be beneficial for health and associated with lower mortality. However, this is not universally observed, and current evidence suggests increased health risks at both ends.