NEW YORK (Reuters Health) - Older people with stronger muscles are at reduced risk of developing Alzheimer's disease compared to their weaker peers, a new study shows.
Dr. Patricia A. Boyle of Rush Alzheimer's Disease Center in Chicago and her colleagues found that the greater a person's muscle strength, the lower their likelihood of being diagnosed with Alzheimer's over a four-year period. The same was true for the loss of mental function that often precedes full-blown Alzheimer's.
Studies have linked grip strength to Alzheimer's, while a person's weight and level of physical activity also influence risk of the disease. To date, however, no one has studied whether muscle strength in and of itself might play a role in dementia risk, Boyle and her team note in November's Annals of Neurology.
"These findings support the link between physical health and cognition in aging and the importance of maintaining good physical function and strength," Boyle told Reuters Health via E-mail.
The researchers measured the strength of nine muscle groups in the arms and legs of 970 dementia-free men and women 54 to 100 years old (their average age was around 80). They also tested the strength of study participants' breathing muscles.
During follow-up, which lasted about four years, 138 people developed Alzheimer's. These individuals were older and had worse mental function than the rest of the study participants. They also were weaker.
But even after the researchers adjusted for age and education level-which can influence Alzheimer's risk-they found that muscle strength had a strong influence on the risk of the disease. People who ranked in the top 10 percent for muscle strength were 61 percent less likely to develop Alzheimer's than the weakest 10 percent. Stronger people also showed a slower decline in their mental abilities over time.
The relationship between muscle strength and mild mental difficulties, which occurred in an additional 275 people, was similar, with the strongest 10 percent being at 48 percent lower risk than the weakest 10 percent.