http://www.cnn.com/2016/03/24/health/exercise-slows-mental-decline-in-older-people/index.html

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(CNN)Mentally, we all slow down a little bit as we age. It gets harder to recall names, or we forget where we put our keys, or the car for that matter. Physically, an older brain doesn't work as fast as it used to. But scientists think there might be one thing that could help slow down this natural aging process.

A study published online this week in Neurology found that older people who exercised regularly experienced a slower rate of mental decline.

In this study, 876 people at an average age of 71 who were a part of the Northern Manhattan Study, a group of people studied for stroke and for the potential to have a stroke, were asked how long and how often they exercised in the two weeks before their in-person interview. 

Among the participants, 90% reported light exercise, such as walking and gardening, or no exercise at all. Those people were placed in the low activity group. The remaining 10% reported moderate to high-intensity exercise, such as running and aerobics, and were placed in the high activity group.

About seven years later, each person was given an MRI and a battery of tests that examined memory and thinking skills. Five years after that, participants took the memory and thinking tests again. 

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