People over 40 should work three days a week if they want to avoid decreased brain function, according to a new Australian study.
The research, carried out by the Melbourne Institute of Applied Economic and Social Research, examined 6,500 adults working a range of hours a week. They were given a series of cognitive function tests — reciting lists of numbers backwards, reading words aloud and matching letters and numbers under time pressure.
Cognitive performance improved with every hour of work the subjects did, until 25 hours a week, at which point it slowly started to decline. Those who worked 55 hours or more were found to perform worse than unemployed and retired people.
Professor Colin McKenzie, one of the study’s co-authors, said: ‘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.
‘The degree of intellectual stimulation may depend on working hours,’ he said. ‘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.’
Geraint Johnes, professor of economics at Lancaster University Management School, told the BBC: ‘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.’
The research, published in the Melbourne Institute Working Paper series, sits uneasily with other recent studies. For example, a report by the Institute of Economic Affairs found that retirement increased clinical depression risk by 40 per cent, which is itself a risk factor for other serious conditions.
There are all kinds of reasons why people may choose to work shorter or longer hours. (The study, for instance, cites the number of dependents, whether parents are still alive, whether benefits are being received and whether there is a mortgage to be paid.) The difference in scores between those who work long and short hours likely depends on a number of different factors. The study fails to adequately explore these and causality between cognitive performance and hours worked does not seem to be convincingly established.
The study signs off with the remark that ‘too much work’ can have negative effects on cognitive ability, but offers little on what ‘too much’ is. Little hope, then, for aspiring GPs or single breadwinners. RM
Research score: 2/5