A lifetime of doing complex work -- particularly work involving complex interaction with people -- may protect against dementia and Alzheimer's disease, according to a pair of studies involving twins.

In one study, researchers examined more than 10,000 twins, 225 of whom had dementia. After accounting for other factors such as age and education, the researchers found a lifetime occupation involving complex work with people was linked to a reduced risk of dementia and Alzheimer's disease. Elements of complex work with people include instructing and supervising others.

The researchers next studied 55 pairs of twins in which one twin had dementia and the other did not. Again, the twins whose occupations involved more complex work were less likely to develop dementia or Alzheimer's disease than their siblings.

One contributing factor may be that people with complex occupations enjoy protective factors such as higher salaries, less exposure to toxins and better access to health care, says researcher Dr. Ross Andel of the University of South Florida in Tampa.

But he adds it is likely vigorous intellectual activity is also protective. "We believe intellectual stimulation has something to do with our findings: It's the complexity of the job that protects against dementia."

With files from The Medical Post