Sweating now pays off later

People who were active as kids better at avoiding dementia in old age

LOS ANGELES — Were you on the tennis team in high school? Did you swim, or run track? Perhaps you spent hours each afternoon in dance class, or maybe the weight room.

If so, here's some good news: All that exercise during adolescence may have protected you against dementia in old age.

Researchers already knew that older people who were physically active were less likely to become cognitively impaired than their couch-potato counterparts. Some studies have shown that workouts during middle age also have a protective effect.

Researchers from Ontario and San Francisco wondered just how far back the effect stretched. They asked 9,395 women 65 or older about their exercise habits during their teens, at age 30, at age 50 and the present day. (Activities such as gardening also counted.)

Women who were physically active at each point in life got higher scores on a cognition test than women who were inactive. When all ages were combined together into a single model that also included factors such as education, smoking habits and body-mass index, the only time when exercise really seemed to matter was during the teenage years.

Unfortunately, those who were focused on sedentary pursuits (video games, debate team) in high school can't go back in time and join JV soccer. But the researchers found that becoming active at older ages was still better than nothing. The women who began exercising by age 30 and kept it up for at least 20 years were still able to cut their risk of cognitive decline in half compared with the women who never caught the exercise bug. The study's results were published in June in the Journal of the American Geriatrics Society.

What accounts for the special power of teen exercise? The researchers aren't sure, but they offered some theories. Adolescents who are physically active have better cognitive performance, and good cognitive performance during youth has been linked to better brain function in old age. Perhaps the exercise helps teens build a "cognitive reserve" for later life, the researchers wrote.

Another possibility is that exercise during the teen years helps stave off chronic medical conditions such as obesity, Type 2 diabetes and hypertension that also carry a greater risk of cognitive decline.

"Physical activity should be encouraged from early life and across the life course to minimize the risk of cognitive impairment in old age," the study concluded.

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