Viewpoint - Vitamin D deficiency

There is a strong case for prescribing higher dosages of vitamin D in elderly patients, says Dr Geoff Venning.

Vitamin D deficiency in adults can only be diagnosed by laboratory measurement of plasma level of calcidiol. This test has revealed a much higher frequency of serious deficiency among elderly people than was previously recognised.

Severe deficiency has been reported in a minority of elderly patients living at home. However, studies show 57 per cent severe deficiency in long-stay wards and 79 per cent in nursing homes and elderly care homes.

Almost all patients in elderly care homes, nursing homes and geriatric long-stay wards develop vitamin D deficiency through lack of exposure to sunlight, combined with declining capacity of the skin to synthesise calcidiol.

Osteomalacia of the pelvis caused by vitamin D deficiency

Effect on muscles
Previous studies and reviews focused on the known effects of vitamin D on bone composition and on the problems of osteoporosis and the prevention of fractures. The new perspective also recognises muscle weakness, body sway and a tendency to fall as a cause of fractures in care homes and long-stay wards. Hip fractures can occur in the elderly even when bone density is normal. Vitamin D levels correlate with muscle strength.

Vitamin D deficiency is one factor that increases the liability to fall and experience fractures. It is common in elderly patients attending fall clinics.

Treatment with vitamin D reduces the risk of falls and fractures, provided that adequate dosages are given. While 400iu daily has been shown to be ineffective clinically, many controlled trials of 800iu daily (or appropriate dosage at longer intervals) have successfully reduced fractures or falls. The 400iu daily dosage has also proved inadequate for prophylaxis of vitamin D deficiency in elderly care homes.

Apart from age and housebound status it has been reported that the prevalence of deficiency is 10 times higher in African-American than in white women in the US. The question of deficiency in women who wear burqas and chadors for religious reasons has not yet been studied, but vitamin D might be appropriate if they have muscle weakness and falls.

The case for routine administration of vitamin D 800iu daily (or appropriate dosage at longer intervals) is overwhelming and incontestable for elderly patients who are housebound or resident in nursing homes, long-stay geriatric wards or elderly care homes.

For ambulant elderly people in the community, the decision is problematic, as vitamin D deficiency affects only a minority. In one study, 250 people needed treatment for a year to prevent one fracture. This figure might be halved for octogenarians.

There is, however, no safety concern. A comprehensive survey has shown that the lowest observed adverse effect level is a concentration of calcidiol corresponding to a daily dosage of 40,000iu, 50 times greater than the effective prophylactic dosage recommended.

  • Dr Venning is a semi-retired independent consultant in pharmaceutical medicine.

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