For the study, Dr Kenneth Rockwood, of Dalhousie University in Halifax, Nova Scotia, and colleagues, examined data on 7,239 people aged 65 and older who were free of dementia when they enrolled in the Canadian Study of Health and Aging.
Five, and then ten years later, participants had new assessments for Alzheimer's disease and all forms of dementia. They also answered questions about 19 health factors that have not been used before to predict dementia. These covered, for example, problems with vision and hearing, arthritis, chest problems, skin problems, denture fit, sinus problems, issues with stomach or bladder, problems with the feet and ankles and broken bones.
At the end of the 10 years, 2,915 of the participants had died, and while the cognitive status of 1,023 of those surviving was not clear, 883 were assessed as cognitively healthy, 677 had cognitive problems but no dementia, 416 had Alzheimer's disease (AD), and 191 had other forms of dementia.
When they analyzed the links between the health factors and the outcomes, Rockwood and colleagues found that:
- For each health factor, the odds of developing dementia went up by 3.2%.
- Older participants with none of the health factors at the start of the study had an 18% risk of having dementia 10 years later.
- However, this risk went up to 30% for those who reported having 8 health problems, and up to 40% for those who had 12.
"... that age-associated decline in health status, in addition to traditional risk factors, is a risk factor for AD and dementia."
"General health may be an important confounder to consider in dementia risk factor evaluation," they added.
Rockwood told the press this suggests "rather than just paying attention to already known risk factors for dementia, such as diabetes or heart disease, keeping up with your general health may help reduce the risk for dementia".
In an accompanying editorial, Dr Jean François Dartigues, of the National Institute of Health and Medical Research (INSERM) in Paris, France, said more studies need to be done to confirm the findings, but if they also find that non-traditional health problems are linked to increased risk of dementia, then this could "lead to the development of preventive or curative strategies for Alzheimer's disease".
Funds from the Canadian Institutes of Health Research, the Nova Scotia Health Research Foundation and the Alzheimer Society of Canada helped pay for the study.
"Nontraditional risk factors combine to predict Alzheimer disease and dementia."
Xiaowei Song, Arnold Mitnitski, and Kenneth Rockwood.
Neurology, Published online before print 13 July 2011.
Link to Abstract.
Additional source: American Academy of Neurology.