Many cases of Alzheimer's disease could potentially be prevented by certain lifestyle measures like quitting smoking and getting more exercise, according to a new report. The findings suggest, but do not prove, that people can take steps to reduce their risk of Alzheimer's, a disease that affects more than 33 million people worldwide.
"Given the current absence of disease-modifying treatments, as well as increasing awareness that symptoms develop over many years or even decades, there has been growing interest in identification of effective strategies for prevention of Alzheimer's disease," explained authors of the report, from the University of California, San Francisco. The findings were published online in The Lancet Neurology, a British medical journal.
For the study, the authors examined the medical literature and identified seven lifestyle factors that may influence the risk of developing Alzheimer's. They looked at stopping smoking, increasing physical activity and mental stimulation, controlling blood pressure and diabetes, and managing obesity and depression. Reducing all seven of these risk factors could prevent as many as 3 million cases of Alzheimer's worldwide, they estimated.
It is uncertain whether any of these lifestyle factors actually promote the development of Alzheimer's. Advancing age and genetics remain the most important risk factors for the disease. But numerous population studies suggest that all may play a role in Alzheimer's onset. Here's what they found.
Diabetes: Having diabetes has been linked to an increased risk of Alzheimer's and other forms of dementia in several studies. More than 10 percent of older Americans have diabetes, so it is important to manage the condition properly, and to take steps to avoid getting diabetes in the first place. Lack of exercise and weight gain can both contribute to diabetes onset.
High blood pressure: Many studies suggest a link between heart health and brain health. Hypertension in middle age, for example, has consistently been linked to an increased risk for Alzheimer's and other forms of dementia in old age. (In old age, on the other hand, low blood pressure has been linked to increased Alzheimer's risk.) People who get treated for high blood pressure have also been shown to be less likely to have cognitive problems down the road.
Obesity: Being overweight in midlife is associated with increased risk of Alzheimer's in old age, numerous studies have shown. (In old age, on the other hand, low body weight is associated with increased dementia risk.) Obesity is a particular problem in the United States.
Depression: People with a history of depression have a two-fold increased risk of dementia compared to those who are not depressed. Getting good medical treatment for depression may improve cognitive function in some people. People who are depressed also tend to be socially withdrawn, and social connection has been shown to lower the risk of Alzheimer's among seniors.
Being sedentary: Physical inactivity has consistently been shown to be linked to an increased risk of Alzheimer's disease. And staying active, whether it's walking, jogging or ballroom dancing, may lower dementia risk. Healthy but sedentary older people who begin exercise programs show improvements in thinking skills.
Smoking: Recent studies report that smoking increases the risk of Alzheimer's. Quitting smoking, in other reports, has been shown to lower the risk of developing dementia.
Low education levels and lack of mental stimulation: There's good evidence that few years of formal education may increase the risk of Alzheimer's disease. Mental stimulation – whether it's doing crossword puzzles, learning a new language or playing a musical instrument – may help lower Alzheimer's risk, It's possible that mental stimulation may enhance connections between brain cells and build up so-called brain reserve. As a result, if some brain cells are destroyed by Alzheimer's, enough remain to delay the onset of symptoms.
The authors found that these seven risk factors may contribute to as many as half of Alzheimer's disease cases worldwide. Lack of exercise remained the most important risk factor in the United States.
The findings are suggestive of lifestyle and health factors that may contribute to Alzheimer’s disease. Anything that may prevent or delay the onset of Alzheimer's in old age could have a dramatic impact on the lives of millions of people and their families.
Source: Deborah E. Barnes, Kristine Yaffe: "The Projected Effect of Risk factor Reduction on Alzheimer's Disease Prevalence." The Lancet Neurology, July 19, 2011.