Long Arms, Legs Linked To Lower Alzheimer’s Risk

Arm and leg length may predict an individuals risk of Alzheimer’s disease and other dementias according to a study published on May 6 in the journal Neurology. The study found that longer arms and greater height at the knee reduced Alzheimer’s disease risk by a small, but significant amount.

American researchers analyzed 2,798 individuals with a mean age of 72 years. During the study 480 (17.2%) of the participants developed dementia over an average follow up period of 5.4 years. The researchers found that for women, a 1 inch increase in arm span led to a 7% decrease in dementia and a 10% decrease in Alzheimer’s disease risk. A 1 inch increase in knee height led to a 16% and 22% decrease in the risk of developing dementia and Alzheimer’s disease respectively.

In men the results were less conclusive with no correlation observed between knee height and Alzheimer’s disease. A longer arm span was associated with a modest reduction in the risk of dementia and Alzheimer’s disease with a 1 inch increase in arm span decreasing dementia risk by 6% and Alzheimer’s disease risk by 8%.

The study found no association between the risk of vascular dementia and knee height while longer arm spans were associated with a statistically insignificant decrease in risk. Vascular dementia is the second most common form of dementia behind Alzheimer’s disease and is caused by impaired blood flow to the brain.

The size of a persons limbs depends on both genetic and lifestyle factors. It is thought that the link between limb size and Alzheimer’s disease is due to the part of the brain that influences limb growth being the same region of the brain that is most severely affected by Alzheimer’s disease.

Poor nutrition and health in a child’s early life may stunt the growth of limbs and it is thought that poor health in early life may increase the probability of developing various health problems, including neurological disorders such as Alzheimer’s disease, in later in life.

The results back up the findings of a Korean study that found a link between longer limbs and improved cognitive performance in elderly people. Other studies have suggested a link between height and Alzheimer’s disease however the correlation appears to be a small one.