Low 25-hydroxyvitamin D predicts the onset of mobility limitation and disability in community-dwelling older adults: the Health ABC Study

• Published in: The journals of gerontology. Series A, Biological sciences and medical sciences Vol. 68; no. 2; pp. 181 - 187
• Main Authors: Houston, Denise K, Neiberg, Rebecca H, Tooze, Janet A, Hausman, Dorothy B, Johnson, Mary Ann, Cauley, Jane A, Bauer, Doug C, Shea, M Kyla, Schwartz, Gary G, Williamson, Jeff D, Harris, Tamara B, Kritchevsky, Stephen B
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01-02-2013
• Subjects: Aged; Aged, 80 and over; Aging - blood; Aging - physiology; Biomarkers - blood; Cohort Studies; Correlation analysis; Demographics; Disabled Persons; Female; Humans; Male; Mobility; Mobility Limitation; Older people; Parathyroid Hormone - blood; Pennsylvania; Proportional Hazards Models; Prospective Studies; Risk assessment; Risk Factors; Tennessee; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - blood
• ISSN: 1079-5006; 1758-535X
• DOI: 10.1093/gerona/gls136

Although 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).
Serum 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.
At 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.
Low 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.