People age 40 and older should only work up to 25 hours per week, according to a study published earlier this year.
Any more than that, and their cognitive abilities are not being used at the maximum level.
The study published in February 2016 by the Melbourne Institute of Applied Economic and Social Research also says females should work fewer hours than males.
There were 6,500 people involved in the study, according to the report.
"Using the test scores of memory span and cerebral dysfunction for the respondents, it is found that working hours up to 25–30 hours per week have a positive impact on cognition for males depending on the measure and up to 22–27 hours for females," the report says. "After that, working hours have a negative impact on cognitive functioning.
"This indicates that the differences in working hours is an important factor for maintaining cognitive functioning in middle and older adults. In other words, in the middle and older age, working part-time could effective in maintaining cognitive ability. It is worth noting that our findings did not show any statistically significant gender differences in the effects of working hours on cognitive functioning," according to the report.
"Our study highlights that too much work can have adverse effects on cognitive functioning."