The role of vitamin D deficiency in hip fractures.
2005
Nordin, B. E. C.
Vitamin D status declines with age in most western societies at moderate latitudes, due to declining sunlight exposure and declining ability of the skin to synthesise cholecalciferol. In ambulant elderly subjects, some seasonal variation in serum 25-hydroxyvitamin D is maintained, but in those in residential care, vitamin D status remains low throughout the year. Although some North American data differ from those elsewhere, possibly due to fortification of milk with vitamin D, nearly all studies worldwide show an association between vitamin D deficiency and hip fracture for at least four reasons. Firstly, because it causes secondary hyperparathyroidism and high bone turnover which is a risk factor for fracture in its own right; secondly, because it causes malabsorption of calcium and osteoporosis; thirdly, because it leads to osteomalacia and a decline in bone quality; and finally, because it increases the incidence of falls due to its adverse effect on muscle strength. Prospective trials and observational studies have shown that vitamin D supplementation (with calcium) can rapidly and significantly reduce hip fracture rates among those in residential care and is likely to have the same effect in community-dwelling subjects selected for low vitamin D status. The evidence suggests that 1,000 units (25 mcg) of vitamin D daily is an effective preventive dose, that cholecalciferol (D<sub>3</sub>) is preferable to ergocalciferol (D<sub>2</sub>), and that calcium supplementation should be part of the regime.
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