Older people who hold temporary or part-time jobs after retirement enjoy better physical and mental health than those who stop working entirely, according to a U.S. study released on Tuesday.

Those who continue to work in their original field also have better mental health than those who change fields, according to a study published in the October issue of the Journal of Occupational Health Psychology published by the American Psychological Association.

The researchers interviewed 12,189 participants, aged 51 to 61, every two years over a six-year period beginning in 1992 about their health, finances, employment and retirement.

The findings are particularly significant, given how many older workers are continuing to work due to the economic downturn, said co-author Mo Wang, a professor of psychology at the University of Maryland.

"Because of the economy, a lot of people don't have enough money to retire," he said.

The retirees who continue to work in temporary or part-time jobs, called bridge employment, suffer 17 percent fewer major diseases than those who stopped working completely, according to the study.

Ranked on a mental health scale, those who continued to work had a 31 percent higher score than those who stopped working, Wang said.

People whose post-retirement jobs are related to their previous careers reported better mental health than those who retired completely. However, people who worked in jobs outside their field after retirement did not show the same mental health benefits, Wang said.

"If you are doing something that is similar to what you were doing in your career, it's easier for you to adjust," he said.

"If you're working on something you are totally not familiar with, or if you're working on something just for the money return, then you have to readjust to the job and for older adults, it's usually pretty challenging," he said.