At least half of all cases of Alzheimer’s disease can be linked to seven major risk factors, and controlling them could sharply reduce the risk of developing the devastating disease, according to researchers from UC San Francisco and the San Francsco VA Medical Center. Leading the list worldwide is lack of education -- specifically not finishing high school -- while living the life of a couch potato is the biggest risk factor in the United States, according to the study presented Tuesday at a Paris meeting of the International Conference on Alzheimer’s Disease and published online in the journal Lancet Neurology. Modifying the risk factors in the population could put a sizable dent in Alzheimer’s incidence, according to the study’s lead author, psychiatrist Deborah Barnes of the VA.
Alzheimer’s disease, which is characterized by a loss of brain function, an inability to care for one’s self and, eventually, death, is a growing problem as the population ages. Worldwide, about 35 million people are thought to suffer from the disease, including nearly 6 million cases in the United States. As the population grows older still, the worldwide total is predicted to triple by the year 2050.
Barnes and her colleagues studied a wide variety of reviews and meta-analyses and then used a sophisticated mathematical program to calculate the risk associated with various factors. They concluded that, worldwide, lack of education contributed 19% of the risk, 14% came from smoking, 13% from lack of physical activity, 10% from depression, 5% from high blood pressure at midlife, 2% from diabetes and 2% from obesity.
In the United States, where lack of education is less common, they found that lack of exercise was the primary risk factor, accounting for 21% of risk. Depression accounted for 15%, smoking for 11%, hypertension for 8%, obesity for 7%, low education for 7% and diabetes for 3%. Barnes noted that, in this country, about a third of the population is largely sedentary, which could account for many cases of Alzheimer’s.
Barnes cautioned that the findings assume that the individual risk factors actually cause Alzheimer’s, which has never been proved. “We are assuming that when you change the risk factor, you change the risk,” she said in a statement. “What we need to do now is figure out whether that assumption is correct.”