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

PLoS One. 2014 Apr 11;9(4):e94479. doi: 10.1371/journal.pone.0094479. eCollection 2014.

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 4,303 participants aged ≥ 60 years from the United States National Health and Nutrition Examination Survey 1999-2004 with mortality data followed up through December 31, 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 ratios, 1.36; 95% confidence interval, 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 (hazard ratios, 1.24; 95% confidence interval, 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Bilirubin / metabolism*
  • Female
  • Humans
  • Male
  • Mortality*
  • Nutrition Surveys*
  • Proportional Hazards Models
  • Racial Groups
  • Smoking / epidemiology
  • Survival Analysis
  • United States / epidemiology

Substances

  • Bilirubin

Grants and funding

This work was supported by the National Health and Medical Research Council of Australia (Grant 1037903). Dr Ong was supported by a Grant-in-Aid (G 12S 6681) from the National Heart Foundation of Australia and the Vice-Chancellor′s Postdoctoral Fellowship from the University of New South Wales. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.