Alzheimer disease, a degenerative and terminal disease for which there is currently no known cure, afflicts 24 million people worldwide.

In its early stages, short-term memory loss is the most common symptom, often initially thought to be caused by aging or stress by the sufferer. Later symptoms include confusion, anger, mood swings, language breakdown and long-term memory loss The research, which studied male and female, showed that women with longer legs had a much lower risk of dementia, with every extra inch of leg reducing their risk by 16 per cent. Women with the shortest arms were 50 per cent more likely to develop the disease than those with the longest arms, according to the study published in the journal Neurology.

US researchers, who ran the study at Johns Hopkins University in Baltimore, suggested that in male only arm length was linked to risk of Alzheimer, with every extra inch lowering their risk by 6 per cent.

They believe that short limbs may be a linked to nutritional deficits early in life that ultimately play a role in brain development. "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," said Tina Huang of Tufts University in Boston, who led the study.

"We found that shorter knee heights and arm spans were associated with an increased risk of dementia," Huang and colleagues wrote.