AUTHOR=Dai Miao , Song Quhong , Wang Xiang , Li Ying , Lin Taiping , Liang Rui , Jiang Tingting , Shu Xiaoyu , Ge Ning , Yue Jirong TITLE=Combined associations of vitamin D and cognitive function with all-cause mortality among older adults in Chinese longevity areas: A prospective cohort study JOURNAL=Frontiers in Public Health VOLUME=11 YEAR=2023 URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2023.1024341 DOI=10.3389/fpubh.2023.1024341 ISSN=2296-2565 ABSTRACT=Objectives

While both vitamin D deficiency and cognitive impairment have individually been linked to a greater risk of all-cause mortality, the combined effects of these two different conditions have not previously been explored in this context. We aimed to investigate the combined impact of vitamin D concentration and cognitive impairment on all-cause mortality in older adults.

Methods

The analyzed data were collected from community-dwelling adults ≥65 years of age that were enrolled in the Chinese Longitudinal Healthy Longevity Survey (n = 1,673). The Mini-Mental Status Examination (MMSE) was used to assess cognitive function, while the plasma 25-hydroxyvitamin D [25(OH)D] test was used to assess vitamin D status. The associations between vitamin D concentration, cognitive function, and all-cause mortality were assessed with Cox proportional hazards models. We used restricted cubic splines to examine the dose–response relationship between vitamin D and the risk of all-cause mortality and used joint effect testing to explore interactions between vitamin D concentration and cognitive function.

Results

During a mean (SD) follow-up of 3.8 (1.9) years, 899 (53.7%) deaths occurred. A negative dose–response relationship was observed between 25(OH)D concentration and cognition impairment at baseline, as well as the odds of all-cause mortality during follow-up. Similarly, cognitive impairment was significantly related to all-cause mortality risk (HR 1.81, 95% CI: 1.54 to 2.12). The combined analyses showed positive associations, with the highest mortality risk observed in older adults with both low vitamin D and cognitive impairment (HR 3.04, 95% CI: 2.40 to 3.86). Moreover, the interaction between 25(OH)D concentration and cognitive function was found to be significant in relation to the risk of mortality (p for interaction <0.001).

Conclusion

Lower plasma 25(OH)D and cognitive impairment were, respectively, associated with increased all-cause mortality risks. The 25(OH)D concentration and cognitive impairment exhibited a combined additive effect on all-cause mortality among older Chinese adults.