Vitamin D insufficiency predicts mortality among older men, but not women: A nationwide retrospective cohort from Thailand.

AIM: Previous studies on the association between low vitamin D level and increased mortality mainly came from high-income countries. The primary objective of the present study was to examine the effect of sex on the association between 25-hydroxyvitamin D2 and D3 and mortality among community-dwelling older people in Thailand.

METHODS: A cohort of individuals aged ≥60 years from the Thai 4th National Health Examination Survey carried out in 2008 were followed and linked to a vital registry in 2015. Data regarding comorbid diseases, physical activity and serum vitamin D were obtained at the baseline assessment. Factors associated with all-cause mortality were determined using Cox proportional hazards models.

RESULTS: A total of 1268 participants with a median age of 74.0 years (interquartile range 67.0-81.0) were included. The prevalence of vitamin D insufficiency was 24.5% and 43.9% in men and women, respectively. Vitamin D insufficiency was significantly associated with all-cause mortality only among men (adjusted HR 1.77, 95% CI 1.25-2.51), but not women. Analysis of 25-hydroxyvitamin D3 divided into tertiles also showed an association with an adjusted HR of 1.83 (95% CI 1.23-2.72) for the lowest tertile in men. Diabetes was an effect modifier for low serum vitamin D and male sex, with HR 3.34 (95% CI 1.76-6.33, P < 0.001) in diabetic men with vitamin D insufficiency.

CONCLUSIONS: Low serum vitamin D is an independent risk factor for increased mortality in community-dwelling Thai older men. Further randomized controlled study to investigate the benefit of vitamin D3 supplementation in older persons, particularly men, is warranted. Geriatr Gerontol Int 2018; 18: 1585-1590.