Association between Urinary Cobalt and All-cause and Cause-specific Mortality among Chinese Older Adults: A Prospective Cohort Study

OBJECTIVE: To investigate the association between urinary cobalt levels and all-cause and cause-specific mortality in older Chinese adults. METHODS: This study enrolled older adults (≥ 60 years) from two cohorts. Urinary cobalt concentrations were quantified using inductively coupled plasma mass spectrometry. Mortality outcomes were ascertained by linking them to the Chinese Disease Surveillance Point System. Cox proportional hazards models were used to evaluate the association between urinary cobalt and mortality, and subgroup analyses were performed to identify vulnerable populations. RESULTS: A total of 9,727 participants were followed for an average of 4.754 years, during which 2,745 deaths were recorded. Participants with the highest urinary cobalt concentration had a 29% greater all-cause mortality risk ( HR: 1.292, 95% CI: 1.155-1.445) than those in the lowest quartile, along with significantly elevated mortality from cardiovascular (24.8%), neurological (137.1%). Subgroup analyses revealed that female, Han Chinese individuals, and rural residents were more susceptible to the effects of cobalt. CONCLUSION: Cobalt exposure was associated with elevated all-cause, cardiovascular, and neurological mortality in older adults, with female, Han ethnicity, and rural residents being vulnerable groups. These findings provide population-based evidence for clinical management and policy revisions regarding cobalt exposure.