Effort–reward imbalance and non-communicable diseases as predictors of sleep quality among Iranian employees

Sleep quality is a key health indicator influenced by various psychosocial and physiological factors. This study aimed to investigate the effects of effort–reward imbalance, and non-communicable diseases (NCDs) on sleep quality among employees. We used the baseline data of 1250 participants included in the Qazvin employee health cohort study, conducted 2021–2022 in northwestern Iran. They were recruited via convenience sampling method. The validated Persian version of the Pittsburgh Sleep Quality Index and Effort–Reward Imbalance (ERI) instruments were used in the cohort study. Additionally, data on sociodemographic factors, lifestyle, body mass index (BMI), and NCDs were collected through interviews. We used both simple/multiple regression and targeted maximum likelihood estimation (TMLE) as our primary analytical approaches. The mean score of total sleep quality was 6.30 ± 3.69. ERI prevalence was 60.47%, and 12% of the study population were smokers. The prevalences of thyroid disorders and fatty liver disease were 11.4% and 11.1%, respectively. The results of the TMLE analysis indicate that depression was associated with a 2.33-point decline in sleep quality (95% CI [0.99, 3.66]). ERI worsened sleep scores by 1.34 points (ATE = 1.34, 95% CI [0.92, 1.76]). Fatty liver (ATE = 0.57, 95% CI [0.03, 1.11]) and cancer (ATE = 0.96, 95% CI [0.18, 1.75]) also showed significant adverse effects. Improving sleep quality among employees may require integrating workplace psychosocial stress reduction strategies with clinical management of chronic conditions. Interventions specifically targeting effort–reward imbalance and depression may yield the greatest benefit.