But there were associations between physical job demands and the brain. People who reported that their job drained them physically turned out also to be people with relatively smaller hippocampal volume and lower scores on their memory tests, even after the researchers controlled for their socioeconomic status, income and whether they exercised during their off hours. Few of these workers were laborers. Most had office jobs. But their brains looked different if they felt that their jobs were physically hard than if they did not.
Outside of work, though, moving was a plus. Those people who reported regular physical activity on their own time generally had greater hippocampal volume and better memories than inactive people. But physical activity at work did not amplify those benefits; it dampened them.
The implications of these results are murky but worrying, says Aga Burzynska, an assistant professor at Colorado State University who led the new study. It is possible that exercise affects the brain one way and “occupational physical activity has a different” and perhaps less-desirable effect, she says.
But many questions remain unanswered. People self-reported their job’s physical demands, she points out; the researchers did not measure energy expenditure, so one person’s draining exertions may have involved filing, while someone else was hefting loaded crates. The researchers also did not delve into workers’ sense of agency, so they do not know if feeling coerced into moving affected outcomes, or how occupational activity could have affected brains at all. Fatigue, stress hormones, differing levels of various brain chemicals or other factors might play a role, Dr. Burzynska says.
Most important, the study does not show that physically demanding work causes brains to change, she says, only that “they are related in some way.”
The findings do suggest, though, that we need to better understand and consider the complex interplay of work, stress, physical activity — on the job and elsewhere — and the health of our brains, Dr. Burzynska says. The relationship between physical demands, our jobs and our brains may be especially relevant now, during the pandemic, when work and home so often overlap.