Working too long is bad for our health, associated with not just weight gain and more alcohol and tobacco use but also higher rates of injury, illness and death. A study that looked at long work hours across 194 countries found a higher risk of heart disease and stroke, leading to about 745,000 attributable deaths. Long work hours are “the largest of any occupational risk factor calculated to date,” the authors wrote.

There is a class divide in overwork in the United States, however. The demand to spend 60 hours at an office is one that depletes the lives of professional, higher-paid workers. What would appear to be an opposite problem plagues those at the lower end of the wage scale. In 2016, about one-tenth of American workers were working part time but trying to get more hours. Despite current hand-wringing that these workers are refusing to come back to the job, thanks to lucrative unemployment benefits, the problem is typically the opposite: People who work in retail or fast food often struggle to get enough hours to qualify for benefits and pay their bills, just to survive.

They also struggle to cobble them together into a predictable schedule. Sixteen percent of American workers’ schedules fluctuate based on their employers’ needs. The people who suffer from just-in-time scheduling that never quite adds up to a normal 9 to 5 aren’t spending their off hours on leisure. They’re working second and third jobs.