A new study has found a connection between working long hours and a heightened risk of developing type 2 diabetes. The new study, the largest in its field to date, indicates that those who worked for 55 hours or more each week working in manual labor or other low socioeconomic status jobs have a 30 percent higher risk of developing type 2 diabetes. Results from the study are published in The Lancet Diabetes & Endocrinology.

The study was conducted by Mika Kivimäki, Professor of Epidemiology at University College London, UK, and colleagues, who performed a systematic review and meta-analysis of published studies along with unpublished individual-level data looking at the effect that working long hours has on the formation of type 2 diabetes up to April 30, 2014.

Data analysis from four published studies and 19 studies with unpublished data involving 222 men and 120 women from the U.S., Europe, Japan and Australia, who were followed for an average of 7.6 years, shows a similar risk of developing type 2 diabetes among people who worked over 55 hours each week and those who worked the typical 35 to 40 hours per week. The researchers, however, discovered vast differences when examining the results more closely.

Additional research showed a 30 percent increased risk of developing type 2 diabetes among those who worked lower socioeconomic status jobs in comparison to participants who worked typical 35 to 40 hour weeks despite accounting for health behaviors such as smoking and physical activity along with risk factors such as age, sex and obesity.

Professor Kivimäki said in a statement, “The pooling of all available studies on this topic allowed us to investigate the association between working hours and diabetes risk with greater precision than has been previously possible. 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.”

According to the World Health Organization, type 2 diabetes comprises 90 percent of individuals with diabetes globally.