Lifestyle changes may cut Alzheimer's risk: study

PARIS, 20 july 2011– Up to half of worldwide cases of Alzheimer's disease could be due to modifiable lifestyle risk factors, according to a study released Tuesday based on a mathematical model.

The theoretical analysis suggests that seven known behaviour-related risk factors, taken together, account for 50 percent of the more than 35 million cases of dementia worldwide.

The findings "suggest that relatively simple lifestyle changes such as increasing physical activity and quitting smoking could have a dramatic impact" on the number of Alzheimer's cases over time, said lead researcher Deborah Barnes, a professor at the University of California in San Francisco.

The study, presented at an international Alzheimer's conference in Paris, is among the first attempts to link risk factors with the degenerative brain disease, which causes memory loss, disability and eventually death.

Only a tiny percentage of cases -- about one percent -- are clearly caused by genetic factors.

Otherwise, while the process by which the disease attacks nerve cells in the brain is well known, its origins remain poorly understood.

Barnes and colleagues used a statistical method to measure the percentage of cases which might be attributable, at least in part, to each of the risk factors assessed.

Worldwide, they found that a low level of education was linked to 19 percent of cases, smoking to 14 percent, physical inactivity to 13 percent, depression to 11 percent, mid-life hypertension and obesity to five and two percent, respectively, and diabetes to two percent.

When combined, these seven modifiable risk factors contribute to as many as 17 million Alzheimer's cases worldwide, and about three million in the United States, the study found.

While eliminating harmful lifestyle habits entirely is likely to remain a theoretical exercise, the more realistic goal of reducing them by a quarter would cut the number of cases globally by three million, the researchers calculated.

"The next step is to perform large-scale studies with people to discover whether changing these lifestyle factors will actually lower Alzheimer's risk," Barnes said in a statement.

The number of people afflicted by Alzheimer's is expected to more than triple by 2050 as populations across the planet age.

The disease is characterised by unwanted proteins that form plaque in some areas of the brain, ultimately destroying neurons and leading to irreversible brain damage.

Typical symptoms are memory loss, erratic behaviour and extreme agitation.

Alzheimer's affects 13 percent of people over 65, and up to 50 percent of those over 85.

Exercise, Vitamin D Seem to Cut Alzheimer's Risk: Researchers

12 july 2010-- Physical activity and adequate levels of vitamin D appear to reduce the risk of cognitive decline and dementia, according to two large, long-term studies scheduled to be presented Sunday at the International Conference on Alzheimer's Disease in Hawaii.

In one study, researchers analyzed data from more than 1,200 people in their 70s enrolled in the Framingham Study. The study, which has followed people in the town of Framingham, Mass., since 1948, tracked the participants for cardiovascular health and is now also tracking their cognitive health.

The physical activity levels of the 1,200 participants were assessed in 1986-1987. Over two decades of follow-up, 242 of the participants developed dementia, including 193 cases of Alzheimer's.

Those who did moderate to heavy amounts of exercise had about a 40 percent reduced risk of developing any type of dementia. People with the lowest levels of physical activity were 45 percent more likely to develop any type of dementia than those who did the most exercise. These trends were strongest in men.

"This is the first study to follow a large group of individuals for this long a period of time. It suggests that lowering the risk for dementia may be one additional benefit of maintaining at least moderate physical activity, even into the eighth decade of life," study author Dr. Zaldy Tan, of Brigham and Women's Hospital, VA Boston and Harvard Medical School, said in an Alzheimer's Association news release.

The second study found a link between vitamin D deficiency and increased risk of cognitive impairment and dementia later in life.

Researchers in the United Kingdom analyzed data from 3,325 people aged 65 and older who took part in the third U.S. National Health and Nutrition Examination Survey. The participants' vitamin D levels were measured from blood samples and compared with their performance on a measure of cognitive function that included tests of memory, orientation in time and space, and ability to maintain attention. Those who scored in the lowest 10 percent were classified as being cognitively impaired.

The study found that the risk of cognitive impairment was 42 percent higher in people who were deficient in vitamin D, and 394 percent higher in those with severe vitamin D deficiency.

"It appears that the odds of cognitive impairment increase as vitamin D levels go down, which is consistent with the findings of previous European studies. Given that both vitamin D deficiency and dementia are common throughout the world, this a major public health concern," study author David Llewellyn, of the University of Exeter Peninsula Medical School, said in the news release.

Skin naturally produces vitamin D when exposed to sunlight. However, most older adults in the United States have insufficient vitamin D levels because skin becomes less efficient at producing vitamin D as people age and there's limited sunlight for much of the year.

"Vitamin D supplements have proven to be a safe, inexpensive and effective way to treat deficiency," Llewellyn said. "However, few foods contain vitamin D and levels of supplementation in the U.S. are currently inadequate. More research is urgently needed to establish whether vitamin D supplementation has therapeutic potential for dementia."

Previous research has pointed to a number of factors that may be associated with cognitive decline and Alzheimer's, especially cardiovascular risk factors, said William Thies, chief medical and scientific officer at the Alzheimer's Association.

He added that "the Alzheimer's Association and others have repeatedly called for longer-term, larger-scale research studies to clarify the roles that these factors play in the health of the aging brain."

These new studies "are some of the first reports of this type in Alzheimer's, and that is encouraging, but it is not yet definitive evidence," Thies said in the news release.

More information

The U.S. National Institute on Aging has more about Alzheimer's disease.