September 22, 2008
Physical frailty is common in older men and women, many of whom feel weak and have trouble holding things or walking. A new study suggests that in some cases, frailty in old age may be related to Alzheimer's disease.
The findings come from data from the Rush Memory and Aging Project, a long-term study of the chronic conditions of aging. They appeared in Neurology, the medical journal of the American Academy of Neurology.
The study participants included men and women living in Chicago who were given physical assessments yearly. Tests of physical robustness included how strongly they could grip things, how long it took them to walk eight feet, their body composition in terms of fat and muscle, and how tired they felt.
Researchers did autopsy examinations on the brains of 165 of the study participants who had died. Their brains were checked for the plaques and tangles that are hallmarks of Alzheimer's disease progression, or pathology.
Of the participants in the study, 36 percent of the group had serious memory loss or other signs of dementia. "Interestingly, Alzheimer's disease pathology was associated with physical frailty in older persons both with and without dementia," said study author Dr. Aron S. Buchman of Rush University Medical Center in Chicago.
Studies show that about 7 percent of people over age 65 are considered frail. That number jumps to as high as 45 percent after age 85. Physical frailty has been linked to various brain defects in older people, including infarcts, or small mini-strokes in the brain, as well as Lewy bodies, which may be linked to memory problems. This study suggests that Alzheimer's disease, too, is associated with frailty in the elderly.
"The level of frailty was approximately two times higher in a person with a high level of Alzheimer's disease pathology compared with a person with a low level of Alzheimer's pathology," Dr. Buchman said. The results remained the same regardless of whether a person had a history of other diseases, like heart disease or diabetes, and regardless of their level of physical activity.
A previous study of the same group of participants while they were alive suggested that older people who are physically frail but whose memories were sharp appear to be at higher risk of developing Alzheimer's disease as compared to those who were less frail. "Together both of these studies suggest that frailty can be an early indicator of Alzheimer's disease pathology and may appear before memory loss."
Previous research has also suggested that the slow and steady weight loss of aging may speed up prior to the onset of Alzheimer's disease. [See "Shedding Pounds May Be an Early Indicator of Alzheimer's Disease"]
"These findings raise the possibility that Alzheimer's disease may contribute to frailty or that frailty and Alzheimer's disease share a common cause," Dr. Buchman said. "We theorize that the accumulation of these plaques and tangles in the brain could affect the areas of the brain responsible for motor skills and simple movements years before the development of dementia."
Aron S. Buchman, M.D.; Julie A. Schneider, M.D.; Sue Leurgans, Ph.D.; David A. Bennett, M.D.: "Physical Fraily in Older Persons Is Associated With Alzheimer's Disease Pathology." Neurology, Volume 71, August 11, 2008, pages 499-504.