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Heart disease, strokes and other serious health conditions that affect the circulatory system or brain have long been thought to contribute to an increased risk of dementia, including Alzheimer's disease. Now, a new study suggests that even relatively minor health problems seemingly unrelated to the mind — such as how well dentures fit — may affect a person's risk as well.

Researchers in Canada analyzed data on 7,239 older people who periodically filled out detailed questionnaires about their overall health. As expected, the people with a history of heart disease and other known risk factors were more likely to develop dementia than their peers, but dementia was also linked to more than a dozen other conditions, including arthritis, bone fractures, incontinence, poor eyesight and hearing, sinus trouble and skin problems.

Each of these conditions increased the risk of dementia by only about 3%, but those increases added up fast when the conditions occurred side by side. Study participants with none of the health problems had an 18% chance of developing dementia during the study, whereas those with 12 of the problems had a 40% chance, even after the researchers took into account age and established risk factors for dementia.

"It's worthwhile maintaining good health, because that will be associated with a lower risk of developing problems with your brain, particularly Alzheimer's disease and other dementias," says the lead author of the study, Dr. Kenneth Rockwood, a professor of geriatric medicine and neurology at Dalhousie University, in Halifax, Nova Scotia. "It's worth people doing what they can to stay in the best health they can." LIST:

The researchers aren't sure how conditions such as arthritis might contribute to dementia, but people with a heavy burden of health problems may be less able to fend off the deterioration of the brain that can come with aging, Dr. Rockwood suggests.

Dr. George Grossberg, a geriatric psychiatrist and professor at the St. Louis University School of Medicine in Missouri, says the findings underscore the importance of aggressively treating arthritis, vision and hearing loss, and other health problems in older people.

Addressing these and other conditions is "important for promoting health and may have an additional payoff in decreasing [or] delaying dementia," says Dr. Grossberg, who did not participate in the new study. "There is no downside to vigorously treating frailty in the later years."

In the study, which was published this week in the journal Neurology, Dr. Rockwood and his colleagues used data from the Canadian Study of Health and Aging, a nationally representative study that began in 1989.

None of the participants had dementia or other cognitive problems at the start of the study. After 10 years, roughly 10% of the surviving participants had been diagnosed with Alzheimer's, and another 14% had been diagnosed with another form of dementia. (The diagnoses were not confirmed via autopsy or brain scans in all cases, which the authors say is a key shortcoming of the study.) LIST:

There is no cure for Alzheimer's disease, but the findings suggest that some people may be able to delay or even prevent the disease by maintaining their all-around health and participating in activities that stimulate the mind, says Dr. Jean François Dartigues of the University Victor Ségalen, in Bordeaux, France, who wrote an editorial accompanying the new study.

Perhaps the best thing people can do to stay physically healthy — and thus maintain their brains, too — is to exercise, Dr. Rockwood says. "The good thing about exercise is you kill a lot of birds with one stone," he explains.

Stuart W.S. MacDonald, an associate professor of psychology at the University of British Columbia, in Canada, who has studied health and dementia but wasn't involved with Dr. Rockwood's research, agrees that older people should exercise, eat a healthy diet, and keep their minds active as much as possible.

"These variables are within everyone's control — and there is emerging evidence to suggest that engaging in each may delay or prevent dementia," he says. "It's never too late to begin engaging in these best lifestyle practices."

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• ANNE HARDING / HEALTH.COM