When immigrants first come to a new country, they’re generally healthier than the people who already live there. But as time goes on, their health advantage starts to fade, even if they’re making more money and moving up in society. A study from Bocconi University found a strong connection between health and how immigrants’ sleeping habits change.

Right when immigrants arrive, they sleep a lot more than the locals. But as the years pass in their new home, this sleep advantage disappears. This matters because not getting enough sleep is linked to serious health issues like diabetes, heart problems, obesity, and feeling really down.

Sleep deprived

Looking at Germany, the study showed that after about 10 years, immigrants’ extra sleep time drops by up to 60%, and their satisfaction with sleep is completely gone.

The researchers used info from the German Socio-Economic Panel, which has been asking about sleep since 1984. They looked at people aged 18–59 from 2008 to 2015, with a final group of 118,233 person-years from 33,143 folks.

When immigrants arrive, they sleep about 23 minutes longer, are 52% less likely to get less than six hours of sleep, and 39% less likely to get less than eight hours. They’re also 14% more likely to be happy with their sleep. This sleep bonus is bigger for immigrants with less education or lower wages, but it fades away faster for them.

Work-related stress

The drop in sleep advantage seems tied to jobs. Immigrants with less education and lower pay often have tough jobs that start early in the morning. The decrease in sleep is mostly happening to immigrants who start work between 4 and 6:30 am. People starting work after 6:30 am don’t show a big drop in sleep time.

“This pattern is consistent with the hypothesis that immigrants with lower levels of education may sleep less as a result of the higher levels of psychological stress associated with structural disadvantage and is consistent with previous studies on ethnic penalties in the labor market,” the authors conclude.