Elevated cardiometabolic risk markers associated with shift work and evening chronotype

Background : Shift work-induced circadian disruption has been strongly linked to various cardiometabolic diseases including obesity, diabetes & cardiovascular disease. Limited studies have explored the impact of different variables such as night work durations, intensities and chronotype on cardiometabolic risk. Methods : This study aimed to determine the impact of circadian disruption on cardiometabolic risk markers in shift workers. This case-control study was conducted with 104 male workers (shift workers; n=52, mean age ±SD; 43.3±10.2 and non-shift workers; n=52, mean age ±SD; 41.2±9.8). Shift work status, durations and intensity of night shifts were determined via an interviewer administered questionnaire. Cardiometabolic risk was evaluated through anthropometric (height, weight, waist circumference and body composition), biochemical (fasting glucose and lipid profile), clinical (blood pressure) and dietary assessment (24-hr recalls from normal days and from work days). The chronotype was determined via the Munich Chronotype Questionnaire (MCTQ). Results: Shift-workers had significantly higher mean body fat percentage (31.7, 22.7% p=0.031), systolic blood pressure (138.6, 128.5 mmHg p=0.009), pulse rate (78.7, 72.3 bpm p=0.015), triglycerides (1.60, 1.30mmol/l p=0.021) and LDL-C (3.90, 3.40 mmol/l p=0.012) than non-shift workers. Evening chronotype shift workers had significantly higher visceral fat levels (12.8, 8.90 p=0.001), systolic blood pressure (137.0, 127.6 mmHg p=0.006), pulse rate (82.7, 73.3 bpm p=0.005) and LDL-C (4.00,3.40 mmol/l p=0.039) than shift workers with a morning chronotype. Conclusion: The number of working hours and the duration of current shift work were associated with cardiometabolic risk markers and the evening chronotype was significantly associated with cardiometabolic risk markers. Further research is warranted to elucidate the underlying mechanisms and inform targeted interventions for individuals engaged in shift work, considering chronotypes.