Vitamin D deficiency is associated with functional decline and falls in frail elderly women despite supplementation

Abstract

Purpose

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.

Methods

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.

Results

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.

Conclusions

IOM guidelines may not be adequate for frail elderly. Further study of optimal 25(OH)D levels for maintaining function and preventing falls is needed.