You've heard it before: If you want to remain healthy, eat more fruit and vegetables and less red meat. But scientists now say such a diet also may help prevent Alzheimer's disease.
In fact, mounting evidence indicates the risk factors for heart disease, high blood pressure, diabetes, excess weight, high cholesterol and lack of exercise may play a role in Alzheimer's.
New studies to be presented next week at an international Alzheimer's conference in Stockholm establish the big picture for the first time, giving scientists a better understanding of how to reduce the likelihood of the disease.
Over the last few years, hints of a connection between Alzheimer's and lifestyle have emerged, but scientists have become increasingly interested in investigating such a link and are just now beginning to realize that what is good for the heart may also be good for the brain.
Alzheimer's is a degenerative brain disease that causes memory loss, disorientation, depression and decay of bodily functions. The disease afflicts about 12 million people worldwide, including more than 4 million Americans. It is increasing so fast that more than 22 million people worldwide will be affected by 2025, experts predict.
Scientists do not know what causes the sticky brain deposits that inevitably kill off neural cells until memory disintegrates and ultimately the patient dies. The biggest risk for Alzheimer's is simply age: Alzheimer's cases double with every five years of age between 65 and 85.
"While more research is necessary, especially in the form of prevention trials, we're seeing the strongest evidence yet that there is a relationship between healthy aging and a reduced risk of Alzheimer's," said William Thies, vice president of medical and scientific affairs at the Chicago-based Alzheimer's Association.
Several studies to be presented at the International Conference on Alzheimer's Disease and Related Disorders indicate that people may be able to reduce their chances of developing Alzheimer's by treating high blood pressure.
One 21-year study, by Miia Kivipelto of the University of Kuopio in Finland, examined 1,449 people. It found that the high cholesterol and high blood pressure seemed to be more strongly linked to the risk of developing Alzheimer's than was a certain gene variation.
However, it seems that having high blood pressure only in later life is not connected to Alzheimer's.
"Since high blood pressure can be controlled, we may have identified something people can do to lower their chance of developing Alzheimer's," said Thies, who was not connected with the research.
Researchers at Case Western University School of Medicine and University Hospitals of Cleveland, Ohio, found that a diet of more fruit and vegetables, and less red meat, offers more protection against the development of Alzheimer's.
Collecting data regarding what foods people ate during adulthood, Grace Petot and her colleagues discovered that low-fat diets containing vitamins such as A, C and E in fruit and vegetables are associated with a reduction in risk for Alzheimer's.
Three other studies to be presented at the conference in Stockholm, the largest gathering ever of Alzheimer's researchers, bolster evidence that taking cholesterol-lowering drugs could reduce the chances of developing Alzheimer's.
A study by Dr. Robert Green at Boston University School of Medicine found that people taking cholesterol drugs called statins reduced their risk of developing Alzheimer's by 79 percent. With 2,378 patients, it is the largest study to investigate the connection and the first to include large numbers of black people, who are disproportionately likely to develop Alzheimer's.
The study also found that types of cholesterol-lowering drugs other than statins were not linked with a reduced risk of Alzheimer's.
High cholesterol can narrow the arteries and raise the risk of heart disease. Some researchers think high cholesterol may also affect brain arteries and promote the clumping of the protein beta-amyloid, which is thought to damage the brain in Alzheimer's.
Beta-amyloid occurs normally in the body, but can accumulate in the spaces between brain cells and create plaques in the brain. These plaques are linked to the death of brain cells, causing a gradual loss of memory and control of body function, and leading eventually to death. By the time a patient has noticeable symptoms of Alzheimer's, substantial amounts of amyloid have built up in the brain, experts say.
A study to be presented at the conference by researchers at St. George's Medical School in London found statins dramatically reduced the production of beta-amyloid.
"The small amounts of beta-amyloid normally found in the blood of healthy people are quickly cleared from the brain," said the study's leader Brian Austen. "In the general population, people taking statins to reduce their blood cholesterol, for whatever reason, have a 70 percent reduction rate for Alzheimer's."
Advances in the understanding of how beta-amyloid acts have prompted researchers to focus much of their effort on trying to block plaque formation.
Other research highlights of the conference involve new ways of seeing what's going on inside the brains of Alzheimer's patients. Until recently, Alzheimer's could only be confirmed by examination of the brain after death.
One study outlines how a new dye could show where plaques are located in the brain. The study, conducted by scientists at Uppsala University in Sweden, found the dye went to areas of the brain where plaques are usually seen in autopsies and that very little of the dye lingered in the brains of people who had no mental impairment.
"Having the ability to quantify amyloid deposition in the brain will have a profound impact on our ability to monitor the progression of Alzheimer's as well as gauge the effectiveness of medical treatments," said Thies of the Alzheimer's Association.
The conference, to be held July 20 through July 25, will involve about 4,000 Alzheimer's researchers.