Serum 25-Hydroxyvitamin D, Albumin, and Mortality Among Chinese Older Adults: A Population-based Longitudinal Study.

Context: The associations between serum 25-hydroxyvitamin D concentrations [25(OH)D] and all-cause mortality have been inconsistent in existing literatures. One plausible reason is the interaction of intrinsic vitamin D with other biological conditions such as malnutrition and chronic inflammation.

Objective: To explore the associations between serum levels of 25(OH)D, albumin, and all-cause mortality and further evaluate their interactions in elderly people.

Design: Population-based longitudinal study.

Setting And Participants: Data were obtained from 1834 people aged 65 to 112 who had their serum 25(OH)D and albumin assayed at baseline in 2011. Participants' survival status was ascertained at the 2014 and 2018 follow-up survey waves.

Main Outcome Measures: All-cause mortality.

Results: Among the 1834 participants, both serum 25(OH)D and albumin concentrations were inversely associated with all-cause mortality (Ps < 0.001). In addition, the interaction effect of 25(OH)D and albumin on all-cause mortality was observed among the participants (P = 0.001). In the group with a higher albumin level (≥40 g/L), participants with a lower level of 25(OH)D (<50 nmol/L) had higher risk of mortality than their counterparts (hazard ratio, 1.92; 95% confidence interval, 1.45-2.56), and the association was more pronounced in women. In the group with a lower albumin level (<40 g/L), the associations failed to reach statistical significance in all participants as well as in women and in men.

Conclusions: Serum 25(OH)D and albumin levels were inversely associated with all-cause mortality in Chinese older adults. The association between 25(OH)D and mortality was more pronounced in participants with higher albumin levels.