SEASONAL PREVALENCE OF VITAMIN-D DEFICIENCY IN INSTITUTIONALIZED OLDER ADULTS

OBJECTIVE: To determine the prevalence and seasonal variation of vitam in D deficiency among older residents of longterm care facilities. DES IGN: Cross-sectional survey with 6-month follow-up. SETTING: Three lon g-term care facilities in Toronto. PATIENTS: Persons more than 65 year s old, medically stable, who had resided in the facility for at least 6 months and had no conditions known to interfere with vitamin D metab olism. MEASUREMENTS: Information regarding demographics, past health, and medication use was collected. Mental and functional status were as sessed by questionnaire. Venous blood samples were analyzed for alkali ne phosphatase, calcium profile, albumin, intact parathyroid hormone, 25 hydroxyvitamin D (250HD), and vitamin D binding protein in Septembe r 1994 and March 1995. In a subgroup of patients, bone specific alkali ne phosphatase was measured, and dietary intake of vitamin D was asses sed. RESULTS: A total of 155 subjects completed the study. The mean ag e of the subjects was 83.2 years (SD 7.1), and 47% were female. The me an 25OHD level in the March sample (39.9 nmol/L, SD 19.7) was signific antly lower than the mean 25OHD level in the September sample (44.9 nm ol/L, SD 16.9) (P =.001). The prevalence of vitamin D deficiency in th e osteomalacic range (25OHD ( 25 nmol/L) increased from 9% in the fall sample to 18% after the winter (chi(2) = 4.65, P =.03). The prevalenc e of borderline deficiency or hypovitaminosis D (25OHD <40 nmol/L) inc reased from 38% in the fall sample to 60% in the spring sample (chi(2) = 14.9, P<.001). Dependence in transfers was associated with an incre ased risk of hypovitaminosis D, odds ratio 2.08 (95% confidence interv al 1.08-4.01), dependence in ambulation 2.57 (1.26-5.23), and regular use of a wheelchair 2.17 (1.09-4.31).When entered into a forward condi tional logistic regression model, only dependence in ambulation remain ed significant, with an adjusted odds ratio of 2.57 (95% CI: 1.26-5.18 ). CONCLUSIONS: Vitamin D deficiency and borderline vitamin D status a re common among older residents of long-term care facilities in Canada . Even though this population has limited outdoor exposure, seasonal v ariation in the prevalence of deficiency remains significant. Evaluati on of interventions to improve the status of vitamin D nutrition in th is population is needed.