Associations between frailty and serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations in older Australian men: the Concord Health and Ageing in Men Project.

BACKGROUND: Poor vitamin D status and frailty are common in older people and associated with adverse health outcomes. The aim of this study was to examine the associations between serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels and frailty and components of frailty in older Australian men.
METHODS: Cross-sectional analysis of the Concord Health and Ageing in Men Project, a large epidemiological study conducted in Sydney, Australia, between January 2005 and May 2007. Participants included 1,659 community-dwelling men. Main outcome measurements were frailty (assessed using the Cardiovascular Health Study), frailty criteria comprising five core components: weight loss; reduced muscular strength/weakness; slow walking speed; exhaustion; and low activity level, and the separate components of frailty. Covariates included serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels measured by radioimmunoassay, age, country of birth, season of blood collection, sun exposure, body mass index, vitamin D supplement use, income, measures of health, parathyroid hormone, estimated glomerular function.
RESULTS: Frailty was present in 9.2% of the sample. Low serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels were independently associated with frailty and with four of the five components of frailty (except weight loss).
CONCLUSIONS: 1,25-dihydroxyvitamin D and 25-hydroxyvitamin D levels were independently associated with frailty in older men. This suggests that there might be a number of different biological mechanisms for how low vitamin D status might contribute to the frailty syndrome. In addition, the possibility that improving vitamin D status may specifically influence the incidence and progression of frailty needs to be explored.