Older adults who are overweight do not seem to be at any extra risk of memory decline, a new study suggests.
In fact, researchers found, it was underweight men and women who were more likely to see their memory suffer over time. They speculate that this is because poor nutrition and weight loss may be early manifestations of Alzheimer's disease in some older people.
The findings, reported in the journal Neurology, stand in contrast to research that has linked obesity in middle-age to a greater risk of dementia later in life.
Obesity, cognitive decline not linked
It's thought that obesity in mid-life may raise dementia risk indirectly, by leading to health problems that impair blood flow to the brain, like high blood pressure and diabetes. Experts also theorise that excess fat cells have some direct effect on brain function.
However, in old age, being overweight or obese may not be a liability when it comes to mental function, according to the authors of the new study.
"We do not know yet why being overweight or obese does not increase the risk for cognitive decline in old age," lead study author Dr. Maureen T. Sturman, of Rush University Medical Center in Chicago, said in a statement.
"However being underweight may be a correlate of the initial stages of Alzheimer's disease," she added.
The findings are based on 3 885 adults age 65 and older who took standard tests of memory and other mental functions at the start of the study, then twice more over the next six years.
Underweight people at greater risk
Sturman's team found no relationship between obesity and the risk of memory changes or other signs of mental decline over time. In contrast, study participants who were underweight at the outset were at heightened risk of decline.
"While past studies have found obesity in middle age increases a person's risk for dementia or Alzheimer's disease, our findings show obesity in old age has no effect on a person's memory," Sturman said.
Studies should continue to look at the effect of weight on older adults' mental functioning so that firmer lifestyle advice can be given, Sturman and her colleagues conclude. Older people may do better to focus on healthy eating, physical activity and mental "exercise" - like reading and doing crossword puzzles - than on shedding excess weight, they suggest. - (Reuters Health)
SOURCE: Neurology, online September 19, 2007.
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