Economic researchers in Japan (where there is a culture of long hours and karoshi – death by overwork) analysed the employment habits and cognitive test results of 3,000 men and 3,500 women above the age of 40 in Australia, including retired and unemployed people.
They found that a part-time job is the best balance between keeping the brain stimulated and becoming completely exhausted through stress.
People who worked about 25 hours a week tended to get the best scores. Those who didn’t work at all scored about 20% lower on the series of tests (reading, numbers and patterns).
Working 40 hours a week was linked to a slightly smaller cognitive deficit but working 55 hours or more was worse than being retired or unemployed.
Working over 50-55 hours is known to cause heart problems in men in particular and an increase in error rates and accidents. The Whitehall study of 10,000 civil servants also found that people who worked working 55 hours a week did worse on cognitive tests than those who kept to 40 hours. Despite this body of knowledge the UK government still opted out of the European Working Time Directive.
Many countries have extended or scrapped the state retirement age and many people face the prospect of working into their 70s. Finnish experts have already warned that people may not be physically or mentally capable of sustaining the effort required to continue in their jobs.
Some companies , like BMW, have invested in modifying the workplace to cater for older employees but they are probably an exception.
Marianna Virtanen, a Finnish Occupational Health expert (they are hot on OH in Finland) who led the Whitehall studies in the mid-80s said that the new research seemed to show tat “Middle-aged and older people should limit their working hours to keep their cognitive capacity fit“.
She did wonder whether a long working week caused a drop in cognitive ability or whether a drop in cognitive ability led to people working longer hours to compensate. She conceded however that “In certain jobs where there is a lot of intense focus and concentration is needed, working long hours may be more exhausting to cognition“.