People shouldn't be working any more than 39 hours a week if they want to protect their wellbeing, a new study has found.

Researchers from Australian National University used data from 8,000 working adults as part of the Household, Income and Labour Dynamics in Australia Survey.

They found the work limit for a healthy life should be set at 39 hours a week, rather than the 48-hour week limit set internationally about 80 years ago.

Working beyond 39 hours, the researchers said, also puts employees at risk of developing mental health problems.

Study co-author Professor Lyndall Strazdins, from the Research School of Population Health at the university, said almost a quarter of Australians worked longer than the recommended 39 hours.

Call for national debate on work hours

The study also found when men and women were considered separately, the healthy work limit was 34 hours per week for women once other commitments were considered.

What is a 'standard' work week? In Australia, the National Employment Standards specify that employers must not ask full time employees to work more than 38 hours a week "unless the additional hours are reasonable"

In Australia, the National Employment Standards specify that employers must not ask full time employees to work more than 38 hours a week "unless the additional hours are reasonable" There is not one strict definition of what constitutes "reasonable" additional hours. What is "reasonable" for one workplace can be different to what's considered acceptable in another

There is not one strict definition of what constitutes "reasonable" additional hours. What is "reasonable" for one workplace can be different to what's considered acceptable in another According to the NES, factors to be taken into account include risks to the health and safety of the employee, family responsibilities, the needs of the workplace, whether penalty rates are available and usual patterns of work in the industry in question

According to the NES, factors to be taken into account include risks to the health and safety of the employee, family responsibilities, the needs of the workplace, whether penalty rates are available and usual patterns of work in the industry in question Internationally, UN conventions (not ratified by Australia) dating back to 1919 mandate a maximum 48-hour working week

The healthy work limit for men was significantly higher — up to 47 hours a week.

The researchers said this was because generally, men spent much less time on care or domestic work than women.

"Women are doing other work — much more extra work outside the labour market," she said.

Professor Strazdins said Australians needed to dispel the widespread belief that people had to work long hours in order to do a good job.

"My message is to their managers and our policy makers to start a national debate on how long is too long," she said.

She said employers must look for ways to support people to work shorter hours.

"And [they shouldn't] expect that they have to work longer hours to hold down that job," she said.

The study was published in the journal Social Science and Medicine.