[Frontiers in vitamin D; basic research and clinical application. Vitamin D and falls]

Along with aging, the synthesis of vitamin D₃ in the skin declines with insufficient sunlight exposure, leading to vitamin D deficiency. In the elderly, vitamin D deficiency results not only in impaired bone mineralization, but also myopathy. Low vitamin D has also been shown to be associated with decline of muscle strength, sarcopenia, functional limitation, and disability. Several recent studies have shown that low serum vitamin D concentration is associated with lower physical function and falls in older adults. The previous study of Japanese community elderly aged 65 years and older has also shown that low serum 25-hydroxyvitamin D [25 (OH) D] level is significantly associated with inferior physical performance and experience of fall. In this chapter, a prospective follow-up study conducted to clarify the association between serum 25 (OH) D level and the risk of falls is introduced. The subjects were the community-dwelling elderly women aged 75 years or older (n = 1,393) who participated in a mass health examination. The baseline prevalence of 25 (OH) D insufficiency [blood level<20 ng/mL] was 35.2%. In a multiple logistic regression model adjusted for age, women in the lowest tertile of 25 (OH) D (≤ 19 ng/mL) were at significantly higher risk of any fall (OR = 1.56 ; 95% CI = 1.14-2.14 ; p = 0.005) and recurrent fall (OR = 1.75 ; 95% CI = 1.15-2.68, p = 0.010) compared to women in the highest tertile [25 (OH) D ≥ 25 ng/mL] . A multiple logistic regression model adjusted for various confounding variables showed that serum 25 (OH) D level was independently associated with the risk of falls (p = 0.023) . In conclusion, these results indicate that lower 25 (OH) D, particularly levels below 20 ng/mL, is independently and significantly associated with an increased risk of falling.