Researchers found an apparent link between heavy drinking or heavy smoking by people in their 40s and the development of Alzheimer's disease decades later, Health Day News reported April 16.

One study of people 60 and older diagnosed with possible or probable Alzheimer's found earlier onset for the disease for heavy drinkers -- 4.8 years earlier for those who had consumed more than two drinks a day -- and for heavy smokers -- 2.3 years earlier for those who had smoked a pack of cigarettes or more a day.

"The current thinking is that the pathology of Alzheimer's disease builds up over many years before clinical symptoms are manifest," said Dr. Ranjan Duara, director of the Mount Sinai Medical Center Wien Center for Alzheimer's Disease in Miami Beach. "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."

Duara noted that both smoking and drinking can damage the brain. However, while it is agreed that any amount of smoking is bad, Duara said there remains "a bit of controversy" about heavy drinking and Alzheimer's, especially what amount of alcohol, if any, is safe.

"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.

Rachel Whitmer, a research scientist with the Kaiser Permanente division of research in Oakland believes "... people need to be thinking about their risk factors for Alzheimer's disease even in their 40s. What is good for your heart is also good for your brain."

The research was presented at the American Academy of Neurology's annual meeting in Chicago.