Staying active, both mentally and physically, may reduce the risk of Alzheimer's disease, researchers report.

In a new study, the odds of developing Alzheimer's were nearly quadrupled in people who were less active during their leisure time between the ages of 20 and 60 compared with their peers. This seemed to be true regardless of the type of activity, although spending time in intellectual pursuits appeared to be the most beneficial.

It is still uncertain whether an inactive lifestyle itself increases the risk of Alzheimer's disease or simply reflects the earliest stages of the disease, but according to the study's lead author, it is a good idea to keep the brain in shape throughout life.

A passive life is not best for the brain. The brain is an organ just like every other organ in the body. Just as physical activity is good for the heart, muscles and lungs, learning is important for keeping the brain healthy.

People often compare the brain to a computer, but there is an important difference. While a computer's hardware does not change, the size and structure of neurons and the connections between them actually change as a person learns.

But exercising the brain means more than hitting the books. In addition,

• traveling
• learning a musical instrument or foreign language
• participating in social and community activities
  

can all help keep the brain active.

Several studies have investigated the connection between work, education and the risk of Alzheimer's disease, and it appears that people who are better educated and more accomplished on the job are less likely to develop the disease. But there has been little research into the effect of leisure activities on the risk of Alzheimer's disease.

The researchers asked about three different types of leisure activities. Physical activities included sports, working out in a gym, biking, gardening, ice skating, walking and jogging.

Examples of intellectual activities included reading, doing puzzles, playing a musical instrument, painting, woodworking, playing cards or board games, and performing home repairs.

Some of the passive activities included watching television, listening to music, attending social clubs, talking on the phone, visiting with friends and attending religious services.

Even after the investigators took into account factors that could have influenced the risk of Alzheimer's, including age, sex, education and socioeconomic status, people who participated in fewer activities than the average were 3.85 times more likely to develop the memory-robbing illness.

The differences between healthy participants and those with Alzheimer's disease were greatest in terms of intellectual activities.

People with Alzheimer's disease were less active in passive, physical and intellectual activities. Since intellectual activities appear to keep the brain healthy, adults should have more opportunities to participate in learning activities, he said. This is especially true for older people, who often are limited in what sort of activities they can participate in.

Unfortunately, many elderly -- and younger people as well -- spend much of their leisure time watching television.

The only activity that Alzheimer's patients performed more frequently than the healthy controls was watching television.

Proceedings of the National Academy of Sciences March 13, 2001;98:3440