Women Lose Weight at Least a Decade Before Diagnosis of Dementia

August 27, 2007 — New research suggests that weight loss precedes a diagnosis of dementia by at least 10 years in women, but not in men.
In a large, retrospective, population-based study, investigators at the Mayo Clinic in Rochester, Minnesota, found no differences in weight between patients and control subjects for 21 to 30 years before onset of dementia. However, women who were destined to develop dementia began losing weight up to 20 years before the disease was diagnosed — a finding that was not observed in men.
"The differences in weight observed between men and women with dementia are likely mediated by personality — social factors rather than purely biological abnormalities. Changes in motivation, personality, initiative, and level of apathy are part of the disease and are also principal contributors to a loss of interest in food. Women who develop dementia are much more likely than men to be involved in making meals, and, therefore, it is likely a loss of interest in food preparation and eating during the prodromal phase of the disease has an impact on their weight," principal investigator David Knopman, MD, told Medscape.
The study is published in the August 21 issue of Neurology.
No Weight Difference in Men
Although several studies have reported that weight loss precedes the onset of dementia, others suggest that obesity in midlife or even in later life may be a risk factor for dementia.
To address this discrepancy, investigators used the Rochester Epidemiology Project — a unique medical records-linkage system that documents the care delivered to the local population of Rochester and Olmsted County, Minnesota, since 1935 in a single database — to look at the issue of weight in the years preceding incident dementia.
Investigators ascertained all incident cases of dementia occurring in Rochester, Minnesota, between January 1, 1990, and December 31, 1994. Cases were individually matched by age and sex to a control from the same population.
Body weights and height were abstracted from the medical records at 6 time points beginning with the year of onset of dementia (index year) and moving backward to 5 to 6, 9 to 10, 11 to 20, 21 to 30, and more than 30 years before a diagnosis of dementia.
A total of 488 cases of incident primary dementia were identified: 355 (72.7%) women and 133 (27.3%) men. However, 7 cases could not be matched to an adequate control, so the final analysis included 481 patients.
The investigators found that although patients and control subjects weighed the same at both 21 to 30 years and more than 30 years before a diagnosis of dementia, those with dementia weighed less than the control subjects at the 9- to 10-year time point and, on average, weighed 12 pounds less than the controls at the year of diagnosis.
When researchers analyzed men and women separately, they found no significant weight difference between male patients and the controls at any time point.
Not Diagnostically Useful
In comparison, there was a difference in weight between women with dementia and female control subjects for up to 20 years before the onset of dementia. In the 10 years preceding the index year, female control subjects lost an average of 2 pounds, whereas women with dementia lost an average of 8 pounds.
To study possible differences in the association between body weight and dementia by age at onset of dementia, the investigators stratified women with primary dementia by age. They found that both younger and older women showed the same pattern of weight loss at index years. However, in women with late onset of dementia, they found that weight loss began up to 20 years before diagnosis.
However, said Dr. Knopman, the study's findings are not useful for diagnosis.
"The weight loss was so subtle and so small and nonspecific that it should not in any way be construed as being at all useful diagnostically," he said.
On the other hand, he said, weight loss in a person with dementia could indicate an increased need for assistance.
"In my experience, when demented patients, who have been living by themselves and have lost weight, either move in with a family member or to an assisted living facility, or are provided with a 24-hour caregiver, they almost invariably regain the weight," he said.
Unlike some other studies, such as one from Kaiser Permanente in California, the current study showed no association between midlife obesity and later-life dementia. The reasons for these divergent findings are unclear, said Dr. Knopman.
The National Institute on Aging supported this study. Two of the authors have disclosed financial relationships with GE Healthcare, GlaxoSmithKline, Myriad Pharmaceuticals, Elan Pharmaceuticals, and Servier. The remaining authors have disclosed no relevant financial relationships.
Neurology. 2007;69:739-746.