A new study has found that cognitive performance of people over 40 increased as the week progressed up to 25 hours a week, and workers’ performed their best at this peak.
The research, which was published in Australia’s Hilda Report, with data taken from the Household, Income and Labour Dynamics in Australia report, revealed that cognitive function began to decline after 25 hours and that middle-aged person who worked 55 hours revealed results that were worse than those that are unemployed or retired.
One of the authors of the study, Professor Colin McKenzie from Keio University, explained that long working hours cause fatigue and stress, which have a significant effect on cognitive function.
“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 and certain types of tasks can cause fatigue and stress which potentially damage cognitive functions,” he said in an interview with The Independent.
“We point out that differences in working hours are important for maintaining cognitive functioning in middle-aged and elderly adults. This means that, in middle and older age, working part-time could be effective in maintaining cognitive ability.”
The study featured 6 500 participants over 40, 3 000 of whom were men. They were told to recite lists of numbers backward, read words out loud and to match numbers with letters, all of this under pressure.
Participants who did not work over 25 hours were found to have the best scores overall.
“It’s very difficult to identify the causal effects of the type of work on cognitive functions. People may be selected into certain occupations according to the cognitive abilities,” McKenzie said.
“Working full-time – over 40 hours a week – is still better than no work in terms of maintaining cognitive function, but it is not maximising the potential effects of work.”
Speaking to BBC, Professor of Economics at Lancaster University Management School Geraint Johnes agrees with the research to some extent, but feels that the study is not sufficient.
“The research only looks only at over-40s, and so cannot make the claim that over-40s are different from any other workers. What the authors find is that cognitive functioning improves up to the point at which workers work 25 hours a week and declines thereafter,” he explained.
“Actually, at first the decline is very marginal, and there is not much of an effect as working hours rise to 35 hours per week. Beyond 40 hours per week, the decline is much more rapid.”
Additional sources: The Independent, BBC