Researchers in Sweden studied the relationship between body mass index and brain atrophy (loss of brain tissue) in 290 women. The women were born between 1908 and 1922 and had four follow-up examinations between 1968 and 1992. During the final exam, they had a computed tomography (CT) scan to measure for any loss of brain tissue. Body mass index (BMI) is a measure of body fat that shows weight adjusted for height. Overweight is a BMI of 25 to 30 kg/m2. Obesity is a BMI of 30 kg/m2 and above.
An overweight or obese BMI was linked to a loss of tissue specifically in the temporal lobe. Nearly 50 percent (144) of the women had temporal atrophy. At the time of CT scan, their body mass index was an average of 27 kg/m2, which was 1.1 to 1.5 kg/m2 higher than the women without brain atrophy. Overall the women's BMI increased over the 24-year period, but the increase was greater for those who lost tissue in the temporal lobe. The risk of atrophy increased 13 to 16 percent per 1.0 kg/m2 increase in BMI.
"This study indicates that a high BMI is a risk factor for dementia in women. Other studies have reported similar findings," said Deborah Gustafson, PhD, of Sahlgrenska University Hospital in Göteborg, Sweden and also the Medical College of Wisconsin in Milwaukee. "Obesity is another factor that should be actively intervened upon to reduce diseases of advanced aging."
The researchers didn't pinpoint a reason why obesity leads to brain atrophy. They said there are several possible mechanisms.
"Obesity is related to ischemia, hypertension, and cerebrovascular and cardiovascular diseases. These conditions contribute to an unhealthy vascular system, and therefore, to a higher dementia risk," said Gustafson. "Obesity may also increase the secretion of cortisol, which could lead to atrophy."
The temporal lobe appears to be highly susceptible to the effects of ischemia and other vascular diseases in the brain, and is evidence of cerebral degeneration and neuronal death, Gustafson said.
A related Patient Page in the November 23 Neurology provides background on dementia and obesity. The Patient Page will be available for downloading from www.neurology.org on November 23, or can be obtained in advance from AAN media relations staff.
The study was supported by grants from the Swedish Research Council, the Swedish Council for Working Life and Social Research, the Alzheimer's Association Stephanie B. Overstreet Scholars, the Alzheimer's Association Zenith Award, Stiftelsen Soderstrom-Konigska Sjukhemmet, Stiftelsen for Gamla Tjanarinnor, Handlanden Hjalmar Svenssons Forskningsfond, Stiftelsen Professor Bror Gadelius' Minnesfond, the Swedish Society of Medicine, the Göteborg Medical Society, Alzheimerfonden, Alma och Anna Yhlen's Foundation, the Göteborg Medical Services and Social Services Administrations, Fredrik and Rosa von Malmborgs Foundation for Brain Research, the Utah Agricultural Experiment Station, and the American Scandinavian Foundation.
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