Researchers at the University of California in San Francisco conducted a review to summarize the evidence regarding seven risk factors for Alzheimer’s disease: diabetes, physical inactivity, hypertension (high blood pressure), smoking, depression, midlife obesity, cognitive inactivity, low educational levels, and physical activity.
They determined that approximately half of worldwide cases of Alzheimer's disease could be caused by lifestyle risk factors that can be changed.
Currently, almost 34 million people worldwide have Alzheimer's disease (AD), and its prevalence is expected to triple over the next 40 years. Their analysis suggests that seven known behavior-related risk factors, together contribute to the development of 50 percent of the cases of dementia worldwide (17.2 million globally and 2.9 million in the US) are potentially attributed to these factors.
According to Deborah Barnes, lead researcher and professor, the findings "suggest that relatively simple lifestyle changes such as increasing physical activity and quitting smoking could have a dramatic impact."
The study was recently presented at an international Alzheimer's conference in Paris, France. It is among the first attempts to link risk factors with the degenerative brain disease, which causes memory loss, disability and eventually death.
Only a very small number 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.
While completely eliminating harmful lifestyle habits entirely is highly unlikely, a more realistic goal of reducing them by twenty-five per cent would decrease 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.
Globally, by 2050, the number of people afflicted by Alzheimer's is expected to more than triple as populations across the planet live longer.
Alzheimer's affects 13 percent of people over 65, and up to 50 percent of those over 85.
Source: The Lancet