Shift work is tough. Whether you’re a night-shift nurse, flight attendant, early morning service rep, or even a bartender, studies show that working odd hours can wreak havoc on your health over time. And now, a new study suggests that working shifts over a 10-year period could be doing weird things to your brain, too.
A large-scale study of more than 3,200 people published in the British Medical Journal suggests that folks who have spent a significant portion of their lives on shift duty experience a noticeable decline in their cognitive abilities. For the paper, French researchers assessed employed and retired shift workers for 10 years, administering speed and memory tests three separate times. Participants were age 32, 42, 52, or 62 at the time of the first measurement, which took place in 1996. They were tested again in 2001, and one last time in 2006.
The result? Shift work was associated with impaired cognition, which was much stronger in people who worked non-9-to-5 gigs all 10 years. The cognitive loss, the researchers write, was “equivalent to 6.5 years of age-related decline.” 6.5 years!
The research team was hesitant to single out a cause, cautioning that a more in-depth look is necessary–but they did float a few theories. One was that the cognitive impairment may have something to do with the disruption of the body’s circadian rhythms, which other studies have shown can lead to physiological stress. But another (and potentially more interesting) hypothesis had to do with a lack of sunlight. They write:
The current study lacked statistical power to satisfactorily assess the possible mediating role of the metabolic syndrome in the observed effects on performance. It has also been suggested that shift workers may be more prone to vitamin D deficiency because of their reduced exposure to daylight, and vitamin D deficiency has also been linked to impaired cognitive functioning.
The good news, though, is that it may be possible to rejuvenate whatever cognitive abilities you might have lost over that decade. The bad news? Regaining all that brainpower takes at least five years of working a normal schedule again.