A new study adds diabetes to the list of health ailments linked with working irregular hours outside of a usual 9-to-5 schedule.
The findings show that people who’ve ever had shift-work jobs have a 9% increased risk of developing diabetes compared with those who consistently worked daytime hours. The study, published online today in Occupational and Environmental Medicine, also showed that the increased risk was highest, 42%, in people who worked rotating shifts involving daytime, evening, and nighttime hours.
Men who worked irregular hours had a 37% increased risk of developing diabetes compared with 9% for women. The researchers called the sex difference “an interesting phenomenon.” They said the finding “suggests that male shift workers should pay more attention to the prevention of [diabetes], and provides a clue for future study of how the biological mechanisms of shift work and [diabetes] are affected by gender.”
The study is a meta-analysis based on 12 studies involving 226 652 participants, including 14 595 who had diabetes. Despite previous research that linked shift work with increased risks of breast cancer and of heart attack, study results attempting to show an association with diabetes have been inconsistent.
But several physiological clues are known, the study authors noted. “Some studies have shown that insufficient sleep and poor sleep quality may develop and exacerbate insulin resistance,” they wrote. “Evidence from epidemiological investigation has confirmed that shift work is associated with weight gain, increase in appetite, and adiposity, which are major risk factors for [type 2 diabetes].” Irregular work hours may influence diabetes risk by leading to harmful changes in blood pressure and cholesterol levels, they added.
Diabetes is a major public health challenge in industrialized and developing countries, the study authors noted. “By the year 2025, the number of cases of type 2 diabetes mellitus will have increased by 65% to reach an estimated 380 million individuals worldwide,” they wrote.