Low Nonfasting Triglycerides and Reduced All-Cause Mortality: A Mendelian Randomization Study

BACKGROUND: Increased nonfasting plasma triglycerides marking increased amounts of cholesterol in remnant lipoproteins are important risk factors for cardiovascular disease, but whether lifelong reduced concentrations of triglycerides on a genetic basis ultimately lead to reduced all-cause mortality is unknown. We tested this hypothesis.

METHODS: Using individuals from the Copenhagen City Heart Study in a mendelian randomization design, we first tested whether low concentrations of nonfasting triglycerides were associated with reduced all-cause mortality in observational analyses (n = 13 957); second, whether genetic variants in the triglyceride-degrading enzyme lipoprotein lipase, resulting in reduced nonfasting triglycerides and remnant cholesterol, were associated with reduced all-cause mortality (n = 10 208).

RESULTS: During a median 24 and 17 years of 100% complete follow-up, 9991 and 4005 individuals died in observational and genetic analyses, respectively. In observational analyses compared to individuals with nonfasting plasma triglycerides of 266–442 mg/dL (3.00–4.99 mmol/L), multivariably adjusted hazard ratios for all-cause mortality were 0.89 (95% CI 0.78–1.02) for 177–265 mg/dL (2.00–2.99 mmol/L), 0.74 (0.65–0.84) for 89–176 mg/dL (1.00–1.99 mmol/L), and 0.59 (0.51–0.68) for individuals with nonfasting triglycerides <89 mg/dL (<1.00 mmol/L). The odds ratio for a genetically derived 89-mg/dL (1-mmol/L) lower concentration in nonfasting triglycerides was 0.50 (0.30–0.82), with a corresponding observational hazard ratio of 0.87 (0.85–0.89). Also, the odds ratio for a genetically derived 50% lower concentration in nonfasting triglycerides was 0.43 (0.23–0.80), with a corresponding observational hazard ratio of 0.73 (0.70–0.77).

CONCLUSIONS: Genetically reduced concentrations of nonfasting plasma triglycerides are associated with reduced all-cause mortality, likely through reduced amounts of cholesterol in remnant lipoproteins.