• Denise K Houston, Rebecca H Neiberg, Janet A Tooze, Dorothy B Hausman, Mary Ann Johnson, Jane A Cauley, Doug C Bauer, M Kyla Shea, Gary G Schwartz, Jeff D Williamson, Tamara B Harris, Stephen B Kritchevsky, and Health ABC Study.
• Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157-1207, USA. dhouston@wakehealth.edu
• J. Gerontol. A Biol. Sci. Med. Sci. 2013 Feb 1; 68 (2): 181-7.

BackgroundAlthough low 25-hydroxyvitamin D (25(OH)D) is prevalent among older adults and is associated with poor physical function, longitudinal studies examining vitamin D status and physical function are lacking. We examined the association between 25(OH)D, parathyroid hormone (PTH), and the onset of mobility limitation and disability over 6 years of follow-up in community-dwelling, initially well-functioning older adults participating in the Health, Aging and Body Composition study (n = 2,099).MethodsSerum 25(OH)D and PTH were measured at the 12-month follow-up visit (1998-1999). Mobility limitation and disability (any/severe difficulty walking 1/4 mile or climbing 10 steps) was assessed semiannually over 6 years of follow-up. The association between 25(OH)D, PTH, and mobility limitation and disability was examined using Cox proportional hazard regression models adjusted for demographics, season, behavioral characteristics, and chronic conditions.ResultsAt baseline, 28.9% of the participants had 25(OH)D <50 nmol/L and 36.1% had 25(OH)D of 50 to <75 nmol/L. Participants with 25(OH)D <50 and 50 to <75 nmol/L were at greater risk of developing mobility limitation (HR (95% CI): 1.29 (1.04-1.61) and 1.27 (1.05-1.53), respectively) and mobility disability (HR (95% CI): 1.93 (1.32-2.81) and 1.30 (0.92-1.83), respectively) over 6 years of follow-up compared with participants with 25(OH)D ≥75 nmol/L. Elevated PTH, however, was not significantly associated with developing mobility limitation or disability.ConclusionsLow 25(OH)D was associated with an increased risk of mobility limitation and disability in community-dwelling, initially well-functioning black and white older adults. Prevention or treatment of low 25(OH)D may provide a pathway for reducing the burden of mobility disability in older adults.

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