The relationship between total bilirubin levels and total mortality in older adults: the United States National Health and Nutrition Examination Survey (NHANES) 1999-2004

Abstract

OBJECTIVE: Due to its anti-oxidant and anti-inflammatory properties, bilirubin has been associated with reduced cardiovascular risk. A recent study demonstrated an L-shaped association of pre-treatment total bilirubin levels with total mortality in a statin-treated cohort. We therefore investigated the association of total bilirubin levels with total mortality in a nationally representative sample of older adults from the general population. METHODS: A total of 4303 participants aged ≥60 years from the United States National Health and Nutrition Examination Survey 1999-2004 with mortality data followed up through 31 December 2006 were included in this analysis, with a mean follow-up period of 4.5 years. RESULTS: Participants with total bilirubin levels of 0.1-0.4 mg/dL had the highest mortality rate (19.8%). Compared with participants with total bilirubin levels of 0.5-0.7 mg/dL and in a multivariable regression model, a lower total bilirubin level of 0.1-0.4 mg/dL was associated with higher risk of total mortality (hazard ratio [HR]=1.36; 95% confidence interval [CI], 1.07-1.72; P=0.012), while higher levels (≥0.8 mg/dL) also tended to be associated with higher risk of total mortality, but this did not reach statistical significance (HR=1.24; 95% CI, 0.98-1.56; P=0.072). CONCLUSION: In this nationally representative sample of older adults, the association of total bilirubin levels with total mortality was the highest among those with a level between 0.1 and 0.4 mg/dL. Further studies are needed to investigate whether higher total bilirubin levels could be associated with a higher mortality risk, compared to a level of 0.5-0.7 mg/dL.