OBJECTIVE–To assess the vitamin D status in homebound, community-dwelling elderly persons; sunlight-deprived elderly nursing home residents; and healthy, ambulatory elderly persons.
DESIGN–A cohort analytic study.
PARTICIPANTS–Of 244 subjects at least 65 years old, 116 subjects (85 women and 31 men) had been confined indoors for at least 6 months, either in private dwellings in the community (the Hopkins Elder Housecall Program) or in a teaching nursing home (The Johns Hopkins Geriatrics Center). The 128 control subjects, a healthy ambulatory group, came from the Baltimore Longitudinal Study on Aging. All subjects were free of diseases or medications that might interfere with their vitamin D status.
MAIN OUTCOME MEASURES–Serum levels of 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (1,25-[OH]2D) were measured in all subjects. In a subgroup of 80 subjects, serum levels of intact parathyroid hormone (PTH), ionized calcium, and osteocalcin and intake of vitamin D (through 3-day food records) were assessed. A randomly selected cohort of sunlight-deprived subjects also had serum levels of vitamin D binding protein measured.
RESULTS–In sunlight-deprived subjects overall, the mean 25-OHD level was 30 nmol/L (12 ng/mL) (range, < 10 to 77 nmol/L [< 4 to 31 ng/mL]) and the mean 1,25-(OH)2D level was 52 pmol/L (20 pg/mL) (range, 18 to 122 pmol/L [7 to 47 pg/mL]). In the sunlight-deprived subjects, 54% of community dwellers and 38% of nursing home residents had serum levels of 25-OHD below 25 nmol/L (10 ng/mL) (normal range, 25 to 137 nmol/L [10 to 55 ng/mL]). A significant inverse relationship existed between 25-OHD (ie, Log [25-OHD]) and PTH when they were analyzed together (r = -0.42; R2 = 0.18; P < .001) and for each cohort separately. All other parameters measured, except ionized calcium, differed significantly from the Baltimore Longitudinal Study Group means. The mean (SD) daily intakes of vitamin D (121  IU) and calcium (583  mg) were below the recommended dietary allowance only in the community-dwelling homebound population. The mean vitamin D binding protein level in the sunlight-deprived subgroup was in the normal range.
CONCLUSIONS–Despite a relatively high degree of vitamin supplementation in the United States, homebound elderly persons are likely to suffer from vitamin D deficiency.