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WEDNESDAY, April 16 (HealthDay News) -- Heavy drinking, heavy smoking and high cholesterol levels in midlife are associated with the onset of Alzheimer's disease in later years, news research shows.
The apparent link between behavior in the 40s and the development of dementia decades later come from two reports presented Wednesday at the American Academy of Neurology annual meeting, in Chicago.
A study of 938 people 60 and older diagnosed with possible or probable Alzheimer's found an earlier onset for the disease for heavy drinkers (more than two drinks a day) and heavy smokers (a pack of cigarettes or more a day), said Dr. Ranjan Duara, director of the Mount Sinai Medical Center Wien Center for Alzheimer's Disease in Miami Beach, Fla.
"The current thinking is that the pathology of Alzheimer's disease builds up over many years before clinical symptoms are manifest," Duara said. "People who start with a good cognitive reserve, who remain active mentally, are able to compensate for the pathology of the brain for a much longer period of time."
The 20 percent of the people in the study defined as heavy smokers developed Alzheimer's 2.3 years sooner than those who were not heavy smokers. Heavy drinkers developed Alzheimer's 4.8 years earlier.
Both smoking and drinking can have a direct physical effect on the brain, damaging cells and synapses, which are the connections between cells, Duara said. While any amount of smoking is bad -- increasing the risk of heart attack, stroke and other medical problems -- there is "a bit of controversy" about heavy drinking and Alzheimer's, he said, specifically, about exactly what "heavy" means.
Studies have shown that moderate drinking can have a beneficial health effect, reducing the risk of coronary disease, Duare said. One influential study, done in the Netherlands, defined moderate drinking as three or four drinks a day. "They consider more than four drinks a day to be severe," he said of the Amsterdam researchers.
Despite those findings, "I suggest that more than two drinks a day is probably not a good idea," Duara said. "No one has shown that one or two a day is not as good as three or four a day in protecting" general health.
It's hard to tell why high blood cholesterol in the 40s should predict Alzheimer's disease in the 70s, but a study of 9,752 California men and women detected the link, said Rachel Whitmer, a research scientist with the Kaiser Permanente division of research in Oakland.
The study found people with total cholesterol levels between 249 and 500 milligrams were one-and-a-half times more likely to develop Alzheimer's disease than those with cholesterol levels less than 198 milligrams. People with total cholesterol levels of 221 to 248 milligrams were more than one-and-a-quarter times more likely to develop the disease.
"We definitely cannot say that this is cause and effect," Whitmer said. "But we know that total cholesterol levels in midlife are predictive of Alzheimer's disease later in life. We can only say that it is a risk factor."
It's not possible to conclude from the study that LDL cholesterol, the "bad" kind that clogs arteries, is responsible for the relationship, she said. In the 1960s and 1970s, when data on the participants were gathered, no distinction had been made between LDL cholesterol and HDL cholesterol, the "good" kind that helps keep arteries open.
"Future studies need to look at that question," Whitmer said.
Meanwhile, "people need to be thinking about their risk factors for Alzheimer's disease even in their 40s," she said. "What is good for your heart is also good for your brain."
More information
You can learn what is known about risk factors for Alzheimer's disease from the Alzheimer's Association.
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