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Low cholesterol, triglycerides associated with all-cause mortality in Native Americans

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October 10, 2017

Among Native American adults with and without diabetes, lower concentrations of serum lipids were associated with increased all-cause mortality and mortality from natural causes, liver disease and external causes. However, the opposite association was observed for cardiovascular mortality, according to study findings reported in Journal of Diabetes and Its Complications.

“Low cholesterol and low triglycerides are widely believed to be beneficial for health and associated with lower mortality,” Stephanie K. Tanamas, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases at the NIH in Phoenix, Arizona, and colleagues wrote. “However, this is not universally observed, and current evidence suggests increased health risks at both ends of the cholesterol and triglyceride distributions.”

Tanamas and colleagues analyzed data from 2,125 Native Americans aged at least 40 years examined biennially between 1993 and 2007 (mean age, 46 years; 61% women; 1,210 with diabetes; 5% using lipid-lowering drugs), as part of a longitudinal study of Native Americans with diabetes in the Southwest United States. Researchers used Poisson regression analysis to calculate age-adjusted mortality rates, with serum lipids as the independent variable and stratified by sex and baseline diabetes status.

Over a median follow-up of 10.1 years, there were 522 deaths (median age at death, 63 years). Of these, 127 were attributed to CVD, 75 were attributed to liver disease and 67 to external causes.

When stratifying patients by diabetes status, researchers observed an association between lower concentrations of total cholesterol, LDL cholesterol, non-HDL cholesterol, triglycerides and triglyceride-to-HDL cholesterol ratio and higher all-cause mortality in those without diabetes. Among adults with diabetes, however, the researchers found a U-shaped relationship between serum lipids and all-cause mortality, apart from triglyceride-to-HDL cholesterol ratio, where a negative relationship was observed, and serum triglycerides, where no relationship was observed. Researchers also found a U-shaped relationship between HDL cholesterol and all-cause mortality for the total cohort.

The researchers observed higher mortality rates for liver disease among men and women with lower concentrations of total cholesterol, LDL cholesterol, non-HDL cholesterol and triglycerides, higher concentrations of HDL cholesterol and a lower triglyceride-to-HDL cholesterol ratio; there were no interactions with sex or diabetes status.

Results differed when looking at CV mortality. Researchers found a greater rate of CV mortality among those with a higher concentration of total cholesterol, LDL cholesterol and non-HDL cholesterol in the total cohort, with an interaction with diabetes for non-HDL cholesterol and an association between total, LDL and non-HDL cholesterol levels and CV morality only in those with diabetes. Researchers observed no associations between HDL cholesterol, triglycerides or triglyceride-to-HDL ratio and CV mortality in the overall cohort, but a positive association was observed in women.

Adjusting for BMI, systolic blood pressure, use of lipid-lowering drugs and alcohol abuse did not alter the findings, according to researchers.

The researchers noted that, in the Native American population, alcohol consumption may partially explain the negative associations between serum lipids, apart from HDL cholesterol, and mortality rates. Native Americans are reported to have lower rates of alcohol use, but higher rates of binge drinking among users than reported in national U.S. surveys, the researchers wrote, adding that lipid concentration is influenced by alcohol consumption and that serum cholesterol and triglycerides are reduced in patients with liver disease.

“It is possible that liver disease was present at the time of the baseline examination resulting in low LDL or non-HDL cholesterol, low triglycerides or high HDL cholesterol, and which subsequently progressed to cause death,” the researchers wrote. “Nevertheless, similar negative associations (positive for HDL cholesterol) were observed with non-liver disease-related deaths, and adjustment for alcohol abuse or excluding deaths within 5 years of baseline did not alter the associations between serum lipids and all-cause mortality, liver disease mortality or mortality due to external causes in the current study.” – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.

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