Shift patterns, physical exercise, and Type 2 diabetes mellitus (T2DM): a prospective cohort study in China

Lay Summary This study investigated the role of different shift patterns and physical exercise on type 2 diabetes mellitus (T2DM) risk factors of shift workers. We hypothesized that shift patterns would be correlated with the incidence of type 2 diabetes and that physical exercise would reduce the risk of type 2 diabetes. We studied 2,827 workers using a cohort study design following for 4 years. The study sample consisted of 1,249 fixed-day-shift workers, 650 three-shift workers, 297 two-shift workers, and 631 four-shift workers. We found that compared with fixed day shift workers, alternating shift workers were at an increased risk for developing T2DM. And moderate and severe physical exercise reduced the risk of T2DM in shift workers. We concluded that physical exercise is associated with decreased type 2 diabetes risk in shift workers, particularly when physical exercise is moderate and severe. The findings of the current study may assist enterprise management departments in developing diabetes interventions among shift workers. To examine the relationships between different shift patterns and Type 2 diabetes mellitus (T2DM) risk, and determine whether physical exercise reduced the incidence of T2DM in shift workers in the oil industry. Baseline data were collected from participants in May 2013 who were then followed for 4 years in a prospective cohort study. The cohort initially consisted of 3,002 workers and ultimately included 2,827 people. Baseline and follow-up questionnaires were sent to participants every 2 years (in May 2015 and May 2017) to update medical and lifestyle information during the follow-up period. The risk of T2DM among two shift workers [relative risk (RR) = 3.442, 95% CI: 1.904-6.799)], three shift workers (RR = 2.534, 95% CI: 1.484-4.571), and four shift workers (RR = 4.230, 95% CI: 2.680-7.518) was higher than that among day workers. An increasing trend was observed with respect to T2DM risk, with the lowest risk in three shift workers, moderate risk in two shift workers, and highest risk in four shift workers. In the interactive analysis between shift work and physical exercise, taking part in mild physical exercise increased the risk of T2DM for workers. Four shift workers who took part in mild physical exercise had an increased risk of T2DM. The relative excess risk due to interaction (RERI) was 33.769 (0.398-67.140). The attributable proportion due to interaction [API (%)] was 0.704 (0.529-0.880). The synergy index (SI) was 3.563 (1.900-6.683). Shift work is significantly correlated with increased incidence of T2DM. Risk of T2DM is lowest risk in three shift workers, moderate in two shift workers, and highest in four shift workers. Shift workers who participated in moderate and severe physical exercise had reduced risk of developing T2DM. Shift work increased the incidence of type 2 diabetes, and moderate and severe physical exercise reduced the risk of developing type 2 diabetes in shift workers.