Institute of Medicine (IOM) guidelines recommend 800 IU vitamin D daily for older adults and maintaining serum 25-hydroxyvitamin D [25(OH)D] above 20 ng/ml for optimal skeletal health. The adequacy of IOM guidelines for sustaining function and reducing falls in frail elderly is unknown.
Female long-term care residents age ≥ 65 enrolled in an osteoporosis clinical trial were included in this analysis (n=137). Participants were classified based on baseline 25(OH)D levels as deficient (<20 ng/ml, n=26), insufficient (20–30 ng/ml, n=40), or sufficient (>30 ng/ml, n=71). Deficient women were provided initial vitamin D repletion (50,000 IU D 3 weekly for 8 weeks). All were supplemented with 800 IU vitamin D 3 daily for 24 months. Annual functional assessments included Activities of Daily Living (ADL), Instrumental ADL (IADL), Physical Performance Test (PPT), gait speed, cognition (SPMSQ), and mental health (PHQ-9). We used linear mixed models for analysis of functional measures and logistic regression for falls.
Daily supplementation maintained 25(OH)D levels above 20 ng/ml in 95% of participants. All groups demonstrated functional decline. Women initially deficient had a greater decline in physical function at 12 (IADL: −2.0±0.4, PPT: −3.1±0.7, both p<0.01) and 24 months (IADL: −2.5±0.6, ADL: −2.5±0.6, both p<0.01), a larger increase in cognitive deficits at 12 months (1.7±0.4: p=0.01), and more fallers (88.5%, p=0.04) compared to those sufficient at baseline, despite supplementation to sufficient levels.