It is said to be the first major study to find vitamin D to be an independent predictor of falls among such women.
"The solution to vitamin D deficiency may simply be supplying safe and readily available vitamin D supplements," said chief investigator in the study, Professor John Wark.
The study found that 22 per cent of hostel residents and a staggering 45 per cent of residents in nursing homes suffer from vitamin D deficiency. Vitamin D is synthesised in the skin during sun exposure. It helps to absorb dietary calcium and is vital in forming and maintaining strong bones.
"Most of us are able to get our daily requirement for vitamin D from sun exposure plus a small amount from our diets. For elderly people in residential care, this is more problematic as most have impaired mobility, therefore more difficulty getting outdoors," said Professor Wark.
"In addition, the skin of elderly people is less effective at producing vitamin D, further compounding the problem. In Australia, there are few dietary sources for vitamin D, so it is very difficult to make up for the lack of vitamin D production in the skin of people with very restricted sunlight exposure," he added.
The findings back results from an earlier study, reported in the BMJ this year, on a group of more than 2,500 over 65s. It found that four-monthly supplementation with vitamin D during a five-year period reduced the incidence of fracture by 22 per cent and fractures in major osteoporotic sites dropped by 33 per cent.
The authors of the new study, published in the November 2003 issue of the Journal of the American Geriatrics Society (vol 51, issue 11, pp 1533-1538), said that vitamin D supplements should be used more widely to prevent this problem.
Other conditions such as impaired cognition and certain medication are known risk factors for falls but the new study, along with other recent research, indicates that muscle strength and avoidance of falls also require adequate vitamin D stores in the body.
The scientists carried out their study on a cohort population in residential care facilities for older people in several states of Australia. More than 650 women in low-level care and around 950 women in high-level care, with a mean age of 84, were followed for an average of five months (145 days) and 168 days respectively.
Serum 25-hydroxyvitamin D levels and recognised risk factors for falls including current medication use, a history of previous fractures, weight, tibial length (as a surrogate for height), cognitive function, walking ability, and frequency of going outdoors were determined.
Falls were recorded prospectively in diaries completed monthly by residential care staff.
After adjusting for weight, cognitive status, psychotropic drug use, previous Colles fracture, and the presence of wandering behavior, blood levels of vitamin D remained independently associated with time to first fall. The researchers also found a 20 per cent reduction in risk of falling with a doubling of the vitamin D level.
The health care cost of falls in the elderly in Australia during the mid-1990s was about A$406 million per year. This figure has been increasing over the past few years and is expected to continue to rise if the situation continues unchecked.
Vitamin D supplementation holds the potential for significant savings in health care costs, in addition to reducing the burden of suffering for the elderly, and reducing risk for osteoporosis, the progressive thinning of bone tissue. The World Health Organisation has defined osteoporosis as the second leading global health care problem after cardiovascular disease.