Cardiovascular Health Effects of Shift Work with Long Working Hours and Night Shifts: Study Protocol for a Three-Year Prospective Follow-Up Study on Industrial Workers

Abstract

There is a plausible association between shift work and cardiovascular disease (CVD), which may be due to disruption of the circadian rhythm causing hormonal changes and metabolic disturbances, resulting in high blood pressure, atherosclerosis, diabetes, and being overweight. However, few studies have investigated the association between several consecutive long work shifts, including night shifts, and risk factors for developing CVD. Moreover, knowledge is lacking on factors that may modify or enhance this suggested relationship. The study period is planned from the third quarter of 2018 to the fourth quarter of 2021, and will involve 125 industrial employees at two Norwegian enterprises producing insulation. The work schedule is either rotating shiftwork (morning, evening, night) or regular day work. At baseline, we will measure blood parameters, including markers of inflammation, lipids, and glycosylated hemoglobin. We will also collect measures of blood pressure, resting heart rate, arterial stiffness, carotid intima-media thickness, and aerobic fitness. At the end of baseline data collection, a subgroup will undergo a supervised high-intensity interval training intervention for eight weeks, initiated by the Occupational Health Service. At one-year follow-up, we repeat baseline measures with added measures of heart rate variability and additional five weeks monitoring of sleep and physical activity, and assessment of respirable dust. At the two year follow-up, we will measure CVD risk factors before and after a planned three-month shutdown in one of the studied plants. We will also assess respirable dust, monitor sleep, and compile a one-year retrospective detailed overview of working hours. A final data collection, similar to the one at baseline, will be carried out after three years. We will use a comprehensive set of methods to identify the effects of shift work with long working hours and night shifts on cardiovascular health. This will provide new knowledge on the association between early manifestations of CVD and occupational exposure to shift work. Further, we can study whether work organization such as extensive overtime, sleep loss, and dust exposure have detrimental effects, and if a three-month cease in shift work or increased physical activity will modify early manifestations of CVD.

Long working hours and risk of cardiovascular outcomes and diabetes type II: five-year follow-up of the Gutenberg Health Study (GHS)

“…Further studies are needed to confirm the results on working hours and arterial stiffness. Upcoming (Lunde et al 2020 ) and future results from occupational cohorts will help to evaluate the significance of arterial stiffness for occupational risk factors and preventive occupational health in general and long working hours in particular. Continued observation should also provide more information regarding the potential differences in long working hours between men and women.…”

Sleep Duration, Number of Awakenings and Arterial Stiffness in Industrial Shift Workers: A Five-Week Follow-Up Study

“…The current study was part of a 3-year prospective follow-up study in relation to cardiovascular health effects of shift work, night shifts and long working hours among industrial workers (see published protocol [ 22 ]). Initially, 94 participants were recruited from two industrial plants in Norway.…”

“…Initially, 94 participants were recruited from two industrial plants in Norway. According to the protocol article preceding the current study [ 22 ], participants with severe cardiovascular and lung disease were excluded from the study. Two additional exclusion criteria were cancer and blood pressure exceeding 180/110 mmHg.…”

“…In a 3-year prospective study of shift workers in two industrial plants in Norway, we analyzed blood parameters, brachial blood pressure, resting heart rate and central blood pressure, augmentation pressure and index, and pulse wave velocity. We performed ultrasound measurement of the carotid arteries, and measured VO 2max [ 22 ]. We found an association between shift work and risk factors for cardiovascular disease such as increased carotid intima media thickness and elevated C-reactive protein (CRP) [ 23 ].…”

Important Difference between Occupational Hazard Exposure among Shift Workers and Other Workers; Comparing Workplace before and after 1980

“…In European countries, shift work is undertaken by 17 percent of the active population [ 10 ]. Several findings throughout the literature review supported that shift work is associated with multiple indicators of poor health and well-being such as a higher rate of cognitive disturbances [ 11 ], cancer [ 12 ], obesity [ 13 ], diabetes [ 14 ], and cardiovascular diseases [ 15 ]. According to the literature, this association between shift work and poorer health could be explained through the disruption of the circadian rhythms, perhaps as a result of physiological and psychological maladaptation to chronically shifted patterns [ 16 ].…”