People who work for more than 55 hours per week doing manual work, or other low-wage jobs, have a 30 percent greater risk of developing type 2 diabetes, according to a new study published in the Lancet Diabetes & Endocrinology.
According to the Centers for Disease Control and Prevention (CDC) 25.8 million people in the United States have diabetes. In 2010, about 1.9 million new cases of diabetes were diagnosed in people ages 20 and older. If current trends continue, one in three American adults will have diabetes by 2050.
Among adults, diabetes is the leading cause of blindness, kidney failure, and amputations of feet and legs not related to accidents or injuries.
Mika Kivimäki, Ph.D., a professor of epidemiology at University College London in the U.K., analyzed four published studies and 19 studies with unpublished data. The studies included 222,120 men and women from the United States, Europe, Japan, and Australia. These people were followed for an average of seven and a half years.
Long Work Hours Raise Diabetes Risk 30 Percent
The study showed that people who work at low-wage jobs, and who work 55 hours or more per week, have about a 30 percent greater risk of developing diabetes, compared to people who work between 35 and 40 hours a week. This was true even after taking into account smoking status and physical activity, and other risk factors such as age, sex, and body weight.
The association remained strong even after excluding the effects of shift work, which has been shown to increase the risk of obesity and type 2 diabetes. In addition, the link between working long hours and diabetes didn’t differ by gender, age, body weight, or region.
Kivimäki said in a press statement, "Although working long hours is unlikely to increase diabetes risk in everyone, health professionals should be aware that it is associated with a significantly increased risk in people doing low socioeconomic status jobs."
Disruptive work schedules that don’t allow people to sleep, exercise, or unwind are one possible explanation for the findings, but more research is needed, researchers said.
Work Bumps Sleep, Exercise Off the Schedule
Orfeu M. Buxton, Ph.D., an associate professor at Pennsylvania State University and the Harvard School of Public Health, told Healthline that the findings are troubling.
"Other types of work that are higher status or aren’t manual labor don’t show this relationship. People working long hours at not the best paying jobs have jobs that are stressful, which causes changes to other behaviors that might help people be most healthy or prevent diabetes,” said Buxton.
Buxton said that to prevent type 2 diabetes, eating a healthy diet, getting enough sleep to feel refreshed, and doing vigorous exercise are crucial, but these behaviors are hard to practice for those who have low paying jobs with long hours.
“What’s needed for exercise for best health is more than just tiring, hard work. After you have worked long hours, you don’t necessarily want to go exercise vigorously," he said.
Workers with long hours may also find it difficult to get sleep. "When we restrict or disrupt sleep, we see greater diabetes risk. We’re not talking extra sleep; we’re talking enough sleep," said Buxton.
Most adults need seven to nine hours of sleep to feel refreshed, but Buxton said people in the United States on average are getting seven hours or less. “A lot of us are carrying a burden of sleep debt all the time, and the stressful, low paying jobs cause people to lose sleep for many years. That may be the mechanism by which long work hours increases diabetes.”
Do people who have physically demanding jobs, such as construction workers and nurses, get enough exercise on the job? Buxton said, "These jobs keep people from getting exercise, and these jobs are not vigorous enough to help with metabolism."
Low-Wage Workers Commute More, Exercise Less
Buxton said people with higher paying desk jobs may spend a lot of time at their desks, but they don't have the same level of physical exhaustion that would prevent them from exercising. "They may be able to protect themselves, or buffer against insults from work,” he said.
People who work 55 hours a week likely have more than one job, and these low-wage workers may also spend many hours commuting on public transportation. This leaves them with less time to pursue healthy behaviors, versus a salaried employee who may have a shorter car ride to work, explained Buxton.
He said, “Diabetes is already a costly and possibly debilitating disease. And somebody who is already not making very much money, plus working hard and working long hours, shouldn't also have to pay the cost of their heath for doing that job.”
Cassandra Okechukwu, ScD, MSN, an assistant professor of social and behavioral sciences at the Harvard School of Public Health, told Healthline that her own research has shown workers in lower socioeconomic positions are under tremendous financial strain to meet their family’s needs.
“Telling them to work less hours is too simplistic and impractical. Diabetes prevention for this group must embrace a broader set of multilevel approaches, from individual interventions addressing sleep quality, to broader policy efforts addressing stagnant wages,” concluded Okechukwu.