Working Over 25 Hours Per Week After Age 40 Could Lead to a Decline in Cognition, Study Finds

A new study from the University of Melbourne finds that working the standard 40 hours per week could lead to a decline in cognition for people over the age of 40.

The study notes that while work can stimulate older workers' brains, long hours can "cause fatigue and physical and/or psychological stress, which potentially damage cognitive functioning." For those over 40, working over 25 hours per week could impair intelligence, while working up to that produced the opposite effect.

Using data from the Household, Income and Labour Dynamics in Australia survey, which asks residents about various work-related topics, the study conducted memory, pattern, and reading tests in more than 6,000 workers over the age of 40.

Colin McKenzie, a professor of economics at Tokyo's Keio University and an author of the paper, told the BBC, that 40 is a tipping point because it's when "most people perform less well at memory tests, pattern recognition and mental agility exercises."

"Work can be a double-edged sword, in that it can stimulate brain activity, but at the same time, long working hours and certain types of tasks can cause fatigue and stress which potentially damage cognition," he told the BBC.

The decline can be attributed to stress and lack of sleep, per McKenzie. But there are other factors. McKenzie hypothesizes that being a caregiver to someone can add additional stress, and creates a job on top of a job.