Every now and then I’ll come across a study that really impresses me because of its use of amazing longitudinal data. There are now studies of the long-term value of high intelligence, the long-term impacts of overwork on physical and mental health, and of course the many studies that have built on the Framingham Heart Study. Still, this new Scottish study of the long-term impact of complex jobs on memory and cognitive ability impresses me.

The researchers put over a thousand elders through a series of memory and cognition tests, and also gathered information about their careers. They also had the subjects IQ scores from when they were 11. Why did they have these figures? Because in 1932 and 1947, almost every 11 year-old child in Scotland was given an intelligence test. (You can read more about the tests here and here. Suffice it to say that the background turns out to be just the sort of mix of science, paternalism, slightly creepy concern about the declining intelligence of the lower orders that lurks in the background of lots of social science and medical research in this era.)

Because something like 95% of Scottish children born in 1921 and 1936 took standardized intelligence tests, they’ve been studied by later generations of researchers, mainly at Edinburgh. These classes, now called LCB 1921 and LBC 1936 (LBC is short for Lothian Birth Cohort), have been the subject of over 200 articles since 2001.

So what did the most recent project find?

According to the American Academy of Neurology, they found that

People whose jobs require more complex work with other people, such as social workers and lawyers, or with data, like architects or graphic designers, may end up having longer-lasting memory and thinking abilities compared to people who do less complex work….

The study found that participants who held jobs with higher levels of complexity with data and people, such as management and teaching, had better scores on memory and thinking tests. The results remained the same after considering IQ at age 11, years of education and the lack of resources in the environment the person lived in (based on information from the area in terms of crime and access to services, for example)….

“These results suggest that more stimulating work environments may help people retain their thinking skills, and that this might be observed years after they have retired,” said study author Alan J. Gow, PhD, of Heriot-Watt University and the Center for Cognitive Aging and Cognitive Epidemiology in Edinburgh, Scotland.

It’s not a huge effect, and there are other factors that are as important to cognitive resource preservation, like staying physically healthy, not smoking, etc.. So why does this matter?

Researchers have debated whether a more stimulating environment may build up a person’s “cognitive reserve,” acting as a buffer allowing the brain to function in spite of damage, or whether people with higher thinking skills are those who are able to go into more challenging occupations.

But the results of this study “actually provide evidence for both theories,” Gow explains:

“Factoring in people’s IQ at age 11 explained about 50 percent of the variance in thinking abilities in later life, but it did not account for all of the difference. That is, while it is true that people who have higher cognitive abilities are more likely to get more complex jobs, there still seems to be a small advantage gained from these complex jobs for later thinking skills.”