Mayo Clinic study finds weight loss precedes dementia diagnosis in women

Rochester, Minn. -- Mayo Clinic researchers have found that women who develop dementia experience a decline in weight as many as 10 years prior to the onset of memory loss, compared to peers who do not develop dementia.

Findings will be presented July 16 at the Alzheimer's Association International Conference on Alzheimer's Disease and Related Disorders in Madrid, Spain.

"We discovered that the weight of those women who developed dementia was drifting downward many years before the onset of symptoms," says David Knopman, M.D., Mayo Clinic neurologist and lead study researcher. "This illustrates changes that occur before the memory loss and mental decline in dementia. We believe that the brain disease began to interfere somehow with maintenance of body weight, long before it affected memory and thinking."

Dr. Knopman and colleagues conducted this retrospective study, analyzing the medical records of people seen by a medical provider in Olmsted County, home of Mayo Clinic, who were diagnosed with the onset of dementia between 1990 and 1994. They identified 560 patients and, for comparison, also identified a group of those similar in age and gender who did not develop dementia. For each patient, weight was identified for the year of dementia diagnosis and then for the 20 to 30 years preceding. The weights of those patients who didn't develop dementia were tracked over the same period.

"In those women who did not go on to develop dementia, 30 years before the year of their peers' onset of dementia, their average weight was 140 pounds," says Dr. Knopman. "At the year of their peers' dementia onset, they weighed 142 pounds. The women who later developed dementia started off at the same weight as those who didn't develop dementia, but then their weight drifted downward to 136 pounds 10 years before symptom onset and 128 pounds at symptom onset."

The cause of the weight loss in those women who later developed dementia is unclear, according to Dr. Knopman, but the investigators have some theories.

"The weight loss findings raise scientific questions about the cause or causes of the weight loss," says Dr. Knopman. "This points to changes in the brain that develop years before the actual memory loss. We think that there are several possible explanations. The women might have less initiative and lose interest in eating, they might develop a duller sense of taste and smell, or they might experience an earlier sense of satiety (feeling full). Also, because we didn't observe the anticipatory weight loss in men, the weight loss could have something specific to do with postmenopausal hormonal changes."

Dr. Knopman explains that he does not consider the weight loss finding to be useful for diagnosis of dementia, and he does not envision that physicians who discover weight loss in their female patients later in life would immediately send the patient for memory testing. He hopes, however, that dementia researchers can pinpoint the brain mechanisms influencing the weight loss in women who develop dementia in order to better understand how it develops.

Dementia is a neurological disorder affecting a person's ability to think, speak, reason, remember and move. The most common forms of dementia are Alzheimer's disease, vascular dementia and Lewy body dementia.

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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