A group of Japanese researchers went through data on Australian working men and women and found that a variety of cognitive skills diminish greatly the longer a work week is employed. The researchers focused on men and women 40 and over.
The study measured cognitive function with scores on three tests, which included reading words aloud, reciting lists of numbers and linking letters and numbers in a certain pattern under time pressure.
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“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 study concludes. “After that, working hours have a negative impact on cognitive functioning.”