Health notes from around the globe.

* In a recent survey conducted by RAND, a Santa Monica, Calif.-based non-profit, investigators polled more than 9,500 Americans and concluded that obesity was linked with more health problems than either alcohol abuse, smoking or poverty. In fact, there are more Americans who are overweight (36 percent of respondents, with 23 percent claiming obesity) than are impoverished (14 percent), heavy drinkers (6 percent) or daily smokers (19 percent).

* Two separate studies have concluded that exercise decreases the chance of mental decline associated with aging.

The first study, reported in the journal Medicine & Science in Sports & Exercise, concluded that older adults who engage in physical activity for more than an hour each day are less likely to suffer a mental decline as they grow older. The study's researchers also noted that there appeared to be a strong association between inactivity and mental decline in individuals who also carried the Alzheimer's gene, or ApoE-4.

The study, which was conducted by lead author Dr. Albertine J. Schuit and colleagues at The National Institute of Public Health and the Environment in Bilthoven (Netherlands), evaluated 347 men whose average age was 75. The study's researchers concluded that the least active men had twice the risk of mental decline than those who performed more than one hour of exercise daily. In addition, men who exercised daily, but for under an hour, were at higher risk for mental impairment, the study found.

And lest we forget the ladies, a recent study led by neurologist Kristine Yaffe, M.D., of the University of California, San Francisco, concluded that women who walk regularly are less likely to experience memory loss and other mental decline associated with aging. The study, which tested the cognitive abilities of nearly 6,000 women aged 65 and older, concluded that women who walked the least were most likely to develop cognitive decline: 24 percent of the least active women had significant decline compared with 17 percent of the most active women. The least active women walked an average of about half a mile a week while the most active group of women walked an average of nearly 18 miles a week.

What was most interesting about the study, however, was that Dr. Yaffe and her colleagues found that for every extra mile walked per week, there was a 13 percent less chance of a decrease in cognitive abilities.

Why does exercise decrease the chances of mental decline in older adults? According to past studies on the benefits of physical fitness, exercise increases blood flow to the brain, which in turn helps maintain healthy oxygen levels. Scientists also believe that regular exercise stimulates nerve cell regeneration and reduces levels of the stress hormone cortisol as well. All of this in turn helps improve mental functioning.