A study has linked exercise in teen years to better mental ability later in life.

This is the VOA Special English Health Report.

How active you are early in life may affect how able-minded you are late in life. That was the finding of a new study of cognitive impairment, or a loss in mental abilities.

The study involved more than 9,000 women in the United States over the age of 65. They answered questions about their level of physical activity as teenagers and at age 30, 50 and late in life.

Laura Middleton of the Sunnybrook Health Sciences Center in Canada led the study.

LAURA MIDDLETON: "People who were physically active on a regular basis had lower risk of cognitive impairments in late life. But it seemed that teenage physical activity was particularly important in terms of the prevention of cognitive impairments."

Speaking by Skype, Laura Middleton noted two long-lasting effects that physical activity can have on teenagers. Exercise could help strengthen the blood vessels that carry blood and oxygen to the brain. Also, physical activity is known to improve the brain's ability to repair itself.

The study is in the Journal of the American Geriatrics Society.

Women who said they were physically active even once a week showed less cognitive impairment as measured by a test. There was not a strong link between the amount of physical activity and the extent of impairment. But the link was strongest among those who were active as teenagers.

Laura Middleton says other studies of exercise and cognitive skills have found a stronger link in women than in men. Still, she says, there is no reason to suggest that the finding about teenage physical activity should not apply to men as well.

Now speaking of teenagers, they were the subject of another new study. It looked at the effects of a later start to the school day.

For the study, an independent high school in Rhode Island delayed morning classes from 8 o'clock to 8:30. The change affected about 200 students in grades nine through twelve.

In online surveys, students reported feeling less sleepy during the day. They rated themselves as less depressed and more active in school. They also reported sleeping longer on school nights and making fewer tiredness-related visits to the school health center.

Judith Owens of the Hasbro Children's Hospital led the study. It appears in the Archives of Pediatrics & Adolescent Medicine.

The study says class attendance improved. It also says teachers and sports coaches had resisted the change. And administrators had planned to return to the 8 o'clock start time after the study. But students and teachers voted to keep the half-hour delay for another term.

And that's the VOA Special English Health Report. I'm Shirley Griffith.

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（来源：VOA 编辑：陈丹妮）