An intellectually demanding job may be the key to living a longer life for someone who has developed young-onset dementia, according to a recent study from Penn State University.

The deterioration of the frontal and temporal parts of the brain leads to a common form of dementia affecting people younger than 65 years old. It results in changes in personality and behavior and problems with language, but does not affect memory.

"[Our] study suggests that having a higher occupational level protects the brain from some of the effects of this disease, allowing people to live longer after developing the disease," researcher Lauren Massimo said in a statement.

Previous studies have suggested that experiences such as education, occupation and mental engagement help a person develop cognitive strategies and neural connections throughout his or her life.

"People with frontotemporal dementia typically live six to ten years after the symptoms emerge, but little has been known about what factors contribute to this range," Massimo said.

For the study, researchers reviewed the medical charts of 83 people who had an autopsy after death to confirm the diagnosis of either frontotemporal dementia or Alzheimer's disease. They also had information about patients' primary occupations.

Researchers determined onset of symptoms by the earliest report from family members of persistently abnormal behavior. Survival was defined as from the time symptoms began until death.

They found that the 34 people autopsied with frontotemporal dementia had an average survival time of about seven years. The people with more challenging jobs were more likely to have longer survival times than those with less challenging jobs.

Based on their findings, occupational level was not associated with longer survival for the people with Alzheimer's disease dementia. The amount of education a person had did not affect the survival time in either disease.

The study was recently published in the journal Neurology.