Middle-aged adults with a high body mass index (BMI) received lower scores on cognitive tests than middle-aged adults with low BMI, according to a study published in the October 10, 2006, issue of Neurology, the scientific journal of the American Academy of Neurology.
The study investigated the relationships between BMI and cognitive function in 2,223 healthy men and women in France through the use of four cognitive tests. The participants, who were between the ages of 32 and 62, were initially tested in 1996 and again five years later.
The study found a higher BMI was associated with lower cognitive test scores. Results from a test involving word memory recall show people with a BMI of 20 remembered an average of nine out of 16 words, while people with a BMI of 30 remembered an average of seven out of 16 words.
"A higher BMI in 1996 was also associated with a higher cognitive decline at follow-up in 2001," said study author Maxime Cournot, MD, with Toulouse University Hospital and the National Institute of Health and Medical Research in Toulouse, France. "The study's findings may be due to a host of factors including the thickening and hardening of cerebral vessels because of obesity or possibly the development of insulin resistance."
While the study found no association between changes in BMI between 1996 and 2001 and cognitive performance, the study did find a slight improvement in cognitive test scores during the five-year time frame.
"This slight improvement may be due to the relatively young age of the participants, who likely had a low incidence of cognitive decline over five years," said Cournot. "The improvement could also be due to an increased familiarization with the tests at follow-up."
Cournot says the prevalence of both dementia and obesity is increasing in epidemic proportions, and the link between BMI and cognitive function could serve as a tool in dementia prevention by managing obesity in middle-age adults.