Vitamin D Supplementation and Older Persons
Vitamin D Supplementation and Older Persons
Objectives: To identify, appraise, and synthesize data from randomized, controlled trials of vitamin D supple-mentation in older people.
Design: A systematic review of trials identified from searches of databases, reference lists, review articles, and recent conference proceedings.
Setting: Most studies performed in ambulatory setting.
Participants: Older people (mean age = 60).
Interventions: Vitamin D or vitamin D metabolites.
Measurements: Strength, physical performance, or falls.
Results: Thirteen trials involving 2,496 patients met this study's inclusion criteria. Most of the trials were small and had methodological problems. In 10 trials, there was no evidence that vitamin D or vitamin D metabolites had an effect on falls or physical function, but three trials showed a positive effect of vitamin D in combination with calcium. When available data from the four highest quality trials were pooled (n 5 1,317), there continued to be no evidence that vitamin D reduced the risk of falling (relative risk = 0.99, 95% confidence interval = 0.89-1.11), although a single trial of vitamin D and calcium showed a positive effect.
Conclusion: Although there is insufficient evidence that vitamin D supplementation alone improves physical performance in older people, some data suggest a benefit from vitamin D combined with calcium supplementation, but this requires confirmation in large, well-designed trials.
Vitamin D, or calciferol, is a prohormone that is essential for the maintenance of calcium homeostasis, and the adverse effects of vitamin D deficiency on the skeleton are well established. Vitamin D is synthesized in the skin after exposure to sunlight or is obtained in the diet. Because vitamin D is stored in the body, supplementation of vitamin D or its active metabolites is relatively straightforward, requiring infrequent single large doses or small doses daily.
There is increasing interest in the effect of vitamin D on extraskeletal tissues. Vitamin D receptors have been identified on many tissues, including muscle, and muscle weakness, limb pain, and impaired physical function are well-recognized manifestations of severe vitamin D deficiency that results in rickets or osteomalacia. Although such extreme deficiency is now relatively rare, levels of vitamin D (i.e., 25 hydroxyvitamin D (25(OH)D)) and muscle strength decline with age, and low levels of vitamin D are associated with reduced physical performance, muscle strength, and physical function and increased risk of falls in older people. However, much of this information is based on cross-sectional studies where cause and effect relationships between exposures and observed outcomes cannot be determined reliably. Because pain, weakness, and fear of falling are all factors that may result in older people restricting their activities and mobility outdoors, it is quite possible that low vitamin D levels are a consequence of illness and disuse that limits outdoor activities and exposure to sunlight. There are few data available on the association between vitamin D and falls and physical function that have been derived from prospective cohort studies, but one small study did not find any association between vitamin D deficiency and mobility or functioning of the upper extremity.
Clinical trials provide the least biased assessment of the effects of vitamin D on muscle and physical functioning. Several small uncontrolled trials conducted in the 1970s suggested that vitamin D supplementation could improve muscle function, particularly in people with low baseline levels of 25(OH)D. Large randomized, controlled trials conducted to determine the effect of calcium and cholecalciferol supplementation on fracture rates in women who were residents of nursing homes or apartments for the elderly generated further interest. After 18 months of treatment, participants who received vitamin D with calcium had 43% fewer hip fractures and 32% fewer nonvertebral fractures. Because the fractures were reduced in the active group soon after randomization, it was suggested that the effect on fractures was due to a reduction in falls as a result of improvements in muscle strength and physical function, but it is not possible to assess reliably the mechanisms of the apparently large treatment effect, because falls were not directly measured in the study. Moreover, given the small number of events, the early reduction in fracture rates from active treatment could be due to small but important changes in bone (e.g., reduced bone turnover) or chance.
Vitamin D could be a simple and widely applicable public health intervention for the promotion of health and physical functioning in older people. In view of the promising but inconclusive early results, this review of randomized, controlled trials was undertaken to assess the effectiveness of vitamin D on muscle strength, physical function, and falls in older people.
Objectives: To identify, appraise, and synthesize data from randomized, controlled trials of vitamin D supple-mentation in older people.
Design: A systematic review of trials identified from searches of databases, reference lists, review articles, and recent conference proceedings.
Setting: Most studies performed in ambulatory setting.
Participants: Older people (mean age = 60).
Interventions: Vitamin D or vitamin D metabolites.
Measurements: Strength, physical performance, or falls.
Results: Thirteen trials involving 2,496 patients met this study's inclusion criteria. Most of the trials were small and had methodological problems. In 10 trials, there was no evidence that vitamin D or vitamin D metabolites had an effect on falls or physical function, but three trials showed a positive effect of vitamin D in combination with calcium. When available data from the four highest quality trials were pooled (n 5 1,317), there continued to be no evidence that vitamin D reduced the risk of falling (relative risk = 0.99, 95% confidence interval = 0.89-1.11), although a single trial of vitamin D and calcium showed a positive effect.
Conclusion: Although there is insufficient evidence that vitamin D supplementation alone improves physical performance in older people, some data suggest a benefit from vitamin D combined with calcium supplementation, but this requires confirmation in large, well-designed trials.
Vitamin D, or calciferol, is a prohormone that is essential for the maintenance of calcium homeostasis, and the adverse effects of vitamin D deficiency on the skeleton are well established. Vitamin D is synthesized in the skin after exposure to sunlight or is obtained in the diet. Because vitamin D is stored in the body, supplementation of vitamin D or its active metabolites is relatively straightforward, requiring infrequent single large doses or small doses daily.
There is increasing interest in the effect of vitamin D on extraskeletal tissues. Vitamin D receptors have been identified on many tissues, including muscle, and muscle weakness, limb pain, and impaired physical function are well-recognized manifestations of severe vitamin D deficiency that results in rickets or osteomalacia. Although such extreme deficiency is now relatively rare, levels of vitamin D (i.e., 25 hydroxyvitamin D (25(OH)D)) and muscle strength decline with age, and low levels of vitamin D are associated with reduced physical performance, muscle strength, and physical function and increased risk of falls in older people. However, much of this information is based on cross-sectional studies where cause and effect relationships between exposures and observed outcomes cannot be determined reliably. Because pain, weakness, and fear of falling are all factors that may result in older people restricting their activities and mobility outdoors, it is quite possible that low vitamin D levels are a consequence of illness and disuse that limits outdoor activities and exposure to sunlight. There are few data available on the association between vitamin D and falls and physical function that have been derived from prospective cohort studies, but one small study did not find any association between vitamin D deficiency and mobility or functioning of the upper extremity.
Clinical trials provide the least biased assessment of the effects of vitamin D on muscle and physical functioning. Several small uncontrolled trials conducted in the 1970s suggested that vitamin D supplementation could improve muscle function, particularly in people with low baseline levels of 25(OH)D. Large randomized, controlled trials conducted to determine the effect of calcium and cholecalciferol supplementation on fracture rates in women who were residents of nursing homes or apartments for the elderly generated further interest. After 18 months of treatment, participants who received vitamin D with calcium had 43% fewer hip fractures and 32% fewer nonvertebral fractures. Because the fractures were reduced in the active group soon after randomization, it was suggested that the effect on fractures was due to a reduction in falls as a result of improvements in muscle strength and physical function, but it is not possible to assess reliably the mechanisms of the apparently large treatment effect, because falls were not directly measured in the study. Moreover, given the small number of events, the early reduction in fracture rates from active treatment could be due to small but important changes in bone (e.g., reduced bone turnover) or chance.
Vitamin D could be a simple and widely applicable public health intervention for the promotion of health and physical functioning in older people. In view of the promising but inconclusive early results, this review of randomized, controlled trials was undertaken to assess the effectiveness of vitamin D on muscle strength, physical function, and falls in older people.
