Let’s be honest: nobody is really a fan of the five-day work week. But if you want a reason to work less, science has your back. If you’re over the age of 40, at least.

According to a report published in the Melbourne Institute Worker Paper, those over the age of 40 are at their most productive when they work three days a week or less.

The researchers came to this conclusion after following 3,000 male and 3,500 female volunteers, Newser explained. During the study, researchers asked the participants to complete cognitive tests and analyzed their work habits, memory, executive reasoning, and abstract reasoning.

The cognitive tests included asking the volunteers to read text backwards, read words aloud, and match numbers and letters under time pressure. As HuffPost explained, the participants' cognitive performance improved as the researchers increased their working hours up to 25 hours. However, after 25 hours the researchers found that performance began to decline in both the male and female volunteers.

Perhaps most surprisingly, HuffPost noted, volunteers who were tasked with working 55 hours a week showed cognitive results that were worse than those who were retired or unemployed.

"Many countries are going to raise their retirement ages by delaying the age at which people are eligible to start receiving pension benefits. This means that more people continue to work in the later stages of their life," study co-author and Keio University professor Colin McKenzie told The Times. "The degree of intellectual stimulation may depend on working hours. Work can be a double-edged sword, in that it can stimulate brain activity, but at the same time long working hours can cause fatigue and stress, which potentially damage cognitive functions.”

McKenzie noted their research points out that “differences in working hours are important for maintaining cognitive functioning in middle-aged and elderly adults” and that working part-time can "be effective in maintaining cognitive ability.”