HEALTH NEWS

Study Title:

Low Vitamin D and Onset of Mobility Problems in Elderly

Study Abstract

Background. 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).

Methods. 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.

Results. 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.

Conclusions. 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.

From press release:

Older adults who don't get enough vitamin D -- either from diet, supplements or sun exposure -- may be at increased risk of developing mobility limitations and disability, according to new research from Wake Forest Baptist Medical Center.


"This is one of the first studies to look at the association of vitamin D and the onset of new mobility limitations or disability in older adults," said lead author Denise Houston, Ph.D., R.D., a nutrition epidemiologist in the Wake Forest Baptist Department of Geriatrics and Gerontology. Houston researches vitamin D and its effects on physical function.

The study, published online this month in the Journal of Gerontology: Medical Sciences, analyzed the association between vitamin D and onset of mobility limitation and disability over six years of follow-up using data from the National Institute on Aging's Health, Aging, and Body Composition (Health ABC) study. Mobility limitation and disability are defined as any difficulty or inability to walk several blocks or climb a flight of stairs, respectively.

Of the 3,075 community-dwelling black and white men and women aged 70-79 who were enrolled, data from 2,099 participants was used for this study. Eligible participants reported no difficulty walking one-fourth mile, climbing 10 steps, or performing basic, daily living activities, and were free of life-threatening illness. Vitamin D levels were measured in the blood at the beginning of the study. Occurrence of mobility limitation and disability during follow-up was assessed during annual clinic visits alternating with telephone interviews every six months over six years.

"We observed about a 30 percent increased risk of mobility limitations for those older adults who had low levels of vitamin D, and almost a two-fold higher risk of mobility disability," Houston said.

Houston said vitamin D plays an important role in muscle function, so it is plausible that low levels of the vitamin could result in the onset of decreased lower muscle strength and physical performance. Vitamin D may also indirectly affect physical function as low vitamin D levels have also been associated with diabetes, high blood pressure, cardiovascular disease and lung disease -- conditions that are frequent causes of decline in physical function. Houston said people get vitamin D when it is naturally produced in the skin by sun exposure, by eating foods with vitamin D, such as fortified milk, juice and cereals, and by taking vitamin D supplements.

"About one-third of older adults have low vitamin D levels," she said. "It's difficult to get enough vitamin D through diet alone and older adults, who may not spend much time outdoors, may need to take a vitamin D supplement."

Current recommendations call for people over age 70 to get 800 International Units of vitamin D daily in their diet or supplements. Houston pointed out that current dietary recommendations are based solely on vitamin D's effects on bone health.

"Higher amounts of vitamin D may be needed for the preservation of muscle strength and physical function as well as other health conditions," she said. "However, clinical trials are needed to determine whether increasing vitamin D levels through diet or supplements has an effect on physical function."

Study Information

Denise K. Houston, et al.
Low 25-Hydroxyvitamin D Predicts the Onset of Mobility Limitation and Disability in Community-Dwelling Older Adults: The Health ABC Study
Journals of Gerontology
2012 May
Wake Forest Baptist Department of Geriatrics and Gerontology