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Published Jul. 8, 2010

It's tempting to stay indoors when the mercury soars, but several studies indicate that spending time in nature improves immune function. Stress reduction is one factor. But scientists also chalk it up to phytoncides, the airborne chemicals that plants emit to protect them from rotting and from insects. One study published in January included data on 280 healthy people in Japan, where visiting nature parks for therapeutic effect is popular. Scientists found being among plants produced "lower concentrations of cortisol, lower pulse rate and lower blood pressure." Other studies have shown that visiting parks and forests raises white blood cells; in one, men who took two-hour walks in a forest over two days had a 50 percent spike in natural killer cells. Another found an increase in white blood cells in women exposed to phytoncides in forest air.

Neck size tells more than BMI

A simple neck measurement may be better than the body mass index (BMI) to measure childhood obesity. In a study published online Monday in the journal Pediatrics, researchers at the University of Michigan's Mott Children's Hospital found neck circumference to be a more convenient and reliable way to assess whether children are overweight or obese. "The body mass index doesn't tell you what is responsible for someone's weight,'' said Dr. Olubukola "Bukky" Nafiu, who led the study, noting muscularity can mean a high BMI. Plus, there's a strong correlation, Nafiu says, between high neck circumference and fat around the middle, considered more dangerous than, say, fat around the hips.

Active teen girls benefit later

People who are physically active at any age appear to be at lower risk for cognitive impairment late in life, and for women, exercise during the teenage years may provide the greatest benefit. A study using data from about 9,395 women 65 and older found that only 8.5 percent of those active during adolescence were cognitively impaired later on, compared with 16.7 percent of those who had been inactive. After adjusting for risk factors like diabetes, researchers concluded that being active as a teen was associated with a 35 percent lower risk for later impairment. The study was published in the Journal of the American Geriatrics Society.

Times wires

"People often separate the body and mind, and forget that physical activity is actually controlled by the brain."

Laura E. Middleton, lead author of a study correlating physical activity with lower risk of dementia