Short Arms, Legs: A Risk for Dementia?

May 6, 2008 -- The length of your arms and legs could help determine your risk for developing Alzheimer's disease and other forms of dementia.

Researchers reporting in the May 6 issue of Neurology say that people with shorter arms and legs have a higher risk for such disease than those with longer limbs, and the findings appear to be most profound among women.

"Our findings are consistent with other studies that have been done in Korean populations, where shorter limb length was associated with greater risk of dementia," researcher Tina L. Huang, PhD, says in a news release. Huang, who was with Johns Hopkins University in Baltimore when the study began, is now with the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston.

Huang's team investigated the relationship between limb length and dementia in an American population by examining data from 2,798 mostly white participants with an average age of 72 who were involved in the Cardiovascular Health Study (CHS). Researchers from that study measured the patient's knee height and arm span.

Knee height equaled the distance from the bottom of the foot to the front surface of the thigh while the knee and ankle were flexed at a 90-degree angle. Arm span was defined as the distance between fingertips when standing with arms outstretched parallel to the floor.

Researched followed the patients for about five years. By the end of the study, 480 patients developed dementia. Those with shorter limb lengths were more likely to develop the neurological condition than those with longer arm spans and knee heights.

Specifically, Huang's analysis showed that:

• Women with the shortest distance from fingertip to fingertip were 1.5 times more likely to develop Alzheimer's disease and dementia.
• A woman's risk of dementia dropped 16% with every additional inch in knee height.
• A man's risk of dementia was associated with a 6% drop with every increased inch in arm span.
• Knee height did not affect a man's dementia risk.

Huang and colleagues theorize that poor nutrition early in life explains the connection between shorter limb length and increased dementia risk. Inadequate nutrition can affect the limb growth.

Several studies have shown that a person's early life environment plays an important role in how likely they are to develop chronic diseases later in life, including neurological conditions such as Alzheimer's disease.

"Body measures such as knee height and arm span are often used as biological indicators of early life deficits, such as a lack of nutrients," adds Huang. "Because the development of the brain region most severely affected by Alzheimer's disease coincides with the greatest change in limb length, we thought it was possible that men and women with shorter limbs could be at greater risk for developing dementia and Alzheimer's disease."