About 80 percent of premature dementia patients have either had to quit their jobs or been fired by their employer, a health ministry survey showed Saturday.

The finding raises doubts about whether companies are helping employees under the age of 65 with dementia to continue working, for instance by shortening their work hours or transferring them to different sections.

The average age of people who develop premature dementia is 51.3. Symptoms vary among individuals, but patients who receive proper treatment at an early stage may be able to slow the advance of the disease.