Vitamin D status of the elderly in relation to age and exposure to sunlight.

Vitamin D status was assessed in 929 men and women aged 65 years and over during a nutrition survey lasting 56 weeks. Concentrations of 25-hydroxyvitamin D (25-OHD) measured in plasma samples showed a seasonal variation, being significantly higher in summer than in winter, and correlated with exposure to sunlight as measured by a 'sunshine score'. Regression analysis showed that 25-OHD concentrations fell with advancing age in both men and women and in summer and winter and approached the same value (about 10 ng/ml) at about the age of 95. This fall has implications in the occurrence of osteomalacia among the elderly and the increasing incidence with age of fractures of the femoral neck.