Serum calcidiol and calcitriol concentrations in elderly people: variations with age, sex, season and disease

The influence of age, sex, seasonal variations and vitamin D supplementation on serum concentrations (s-conc.) of calcidiol and calcitriol were studied in 311 hospitalized and 106 home-living people aged 70 years and over, residing at 60° latitude. The serum calcidiol conc. (meanSD, nmol/L) was reduced in the hospital group compared to the home-living group (males: 40.6 ± 23.2 compared to 59.6 ± 28.9; females: 37.3 ± 22.6 compared to 48.5 ± 20.3) and showed no seasonal variation. The homeliving group showed highest levels in August-September (62.2 ± 26), and lowest levels in January–March (42.9 ± 21). Serum calcidiol declined with age, most prominent in the home group (males: r = −0.13, P = 0.036;females: r = −0.33, P = 0.001). A positive correlation was shown between s-calcitriol and s-calcidiol conc. (r = 0.26, P> 0.001). An increased s-conc. of calcidol was present in those with vitamin supplementation (home: 59.9 ± 26; hospital: 43.4 ± 22) compared to those without supplementation (home: 46.6 ± 22; hospital: 36.2 ± 22), but s-calcidiol conc. did not correlate to nutritional vitamin D intake. Vitamin D deficiency (s-calcidiol conc. < 30 nmol/L) was more common in old people recently admitted to hospital, compared to those living at home. Only the home-living group had the benefit of sunlight exposure, but both groups may benefit from vitamin supplementation.