Geoff Venning, a consultant in pharmaceutical medicine, claims that vitamin D deficiency among elderly people is much more common than previously recognized and is a serious problem for residents of old people's homes, nursing homes, and housebound people in the community.
The deficiency, common among elderly people because of the skin's reduced capacity to synthesise the provitamin calcidiol, may lead to poor muscle strength and weakness. In a study showing that more than a third of people aged over 65 fall each year, the main risk factor was muscle weakness, writes the author in the 5 March issue of the British Medical Journal (330, pp524-526).
The author also notes that housebound elderly people often do not get adequate exposure to sunlight and probably get less exercise than other elderly people. Exercise training can reduce the incidence of falls.
However in a review of studies and the available evidence on vitamin D supplementation, he notes that a high dose (of 800IU) is needed to have any benefit.
In one randomised controlled trial, elderly women given 800 IU vitamin D daily with calcium had a 47 per cent reduction in falls and fractures compared with controls receiving calcium alone over 12 months. In another with a three-month follow-up, the incidence of falls was almost halved and musculoskeletal function improved among elderly people who had 800 IU vitamin D with calcium compared with calcium alone.
Yet two randomised controlled trials have found 400 IU vitamin D daily to be ineffective in reducing the frequency of fractures, writes Venning, and two descriptive studies have noted deficiency despite supplementation at a dose of 400 IU daily.
In contrast, five randomised controlled trials have shown that 800 IU/day of vitamin D significantly reduces the incidence of falls and fractures.
"These high dose studies strengthen the evidence for and the public health importance of preventive treatment with adequate doses of vitamin D among housebound elderly people and suggest priorities for future research," he writes.
A dose of 800 IU daily has a 50-fold margin of safety, according to the author. This amount is also within the guidance level concluded by the UK's expert working group on vitamins and minerals and the EU scientific committee on food.
People over the age of 65 are set to make up a quarter of the total European population by 2020. The most dramatic demographic changes for the future will be in the oldest age group (80 years and over) that is estimated to grow from 21.4 million in 2000 to 35 million in 2025.
Venning predicts that giving supplements to only women with known vitamin D deficiency could prevent one fall for every five women treated for a year and treating 20-25 women in nursing homes and old people's homes for a year without screening for vitamin D status would prevent one fracture.
He adds that the research on vitamin D so far has been carried out with cholecalciferol, which is not available in the United Kingdom except as 400 IU tablets with added calcium. Vitamin D2 (ergocalciferol) is available at a dose of 50 000 IU, which could be taken once every two months to provide an equivalent dose, but this needs testing in clinical trials.