Night Work and Mortality: Prospective Study Among Finnish Employees Over the Time Span 1984 to 2008

Abstract

There is considerable evidence showing that night work is associated with increased morbidity, but only a few studies have focused on its relation to mortality. This study investigates the relationship between the type of working-time arrangement (weekly night work/daytime work) and total and cause-specific mortality among men and women. The data consist of a representative working conditions survey of Finnish employees conducted in 1984 (2286 men/2216 women), which has been combined with register-based follow-up data from Statistics Finland covering the years 1985-2008. In the 1984 survey, the employees were asked if they worked during the night (23:00-06:00 h) and if so, how often. In this study, the authors compare employees who worked at night (121 men/89 women) to daytime employees who did not do night work (1325 men/1560 women). The relative risk of death was examined by Cox proportional hazards analyses adjusted for background (age, level of education, family situation, and county), health (longstanding illness, pain symptoms, smoking status, and psychological symptoms), and work-related factors (weekly working hours, physical and psychological demands, demands of learning at work, and perceived job insecurity). Female employees working at night had a 2.25-fold higher risk of mortality than female dayworkers (95% confidence interval [CI] 1.20-4.20) after adjustment for background and health- and work-related factors. In addition to total mortality, night work was also associated with tumor mortality. Female night workers had a 2.82-fold higher risk of tumor mortality than female dayworkers (95% CI 1.20-6.65) in the adjusted model. Among men, no such significant association was observed. The present study indicated that female night workers had a higher risk of both total and tumor mortality compared to female daytime employees. Additional research on the potential factors and mechanisms behind the association between night work and mortality is required.

Shift work and the risk of cardiovascular disease. A systematic review and meta-analysis including dose–response relationship

“…We only included studies published since 2006, as these tend to be of higher quality and also because our aim was to update the previous meta-analysis. Indeed, the studies that presented estimates for CHD and CVD mortality were published in recent years (2010-2016) and thus most of these (16,18,38) were not included by Vyas et al (7), which may explain some of the different results. Ten studies have reported on shift work and the risk of CVD since the previous meta-analysis (16, 18, 19, 27-29, 34, 38, 39, 41); these are included in our study.…”

“…Other studies considered doing long working hours or weekend work as shift work (34,35). Two studies did not provide a definition of shift work (36,37), while others limited inclusion to fixed night shift workers (38)(39)(40), or considered shift work as any type of work schedule other than fixed day-only work (41).…”

Night-shift work increases morbidity of breast cancer and all-cause mortality: a meta-analysis of 16 prospective cohort studies

“…Studies on the association between elevated NSW and cancer-related mortality have produced contradicting results. Similarly, several prospective cohort studies have reported NSW in relation to all-cause mortality, but the findings were inconsistent [11,15,16]. In addition, the relationship of NSW to cardiovascular events was also unclear [15,[17][18][19][20].…”

“…Recent prospective cohort studies had reported the correlation between NSW and tumor mortality [7,[11][12][13][14]. Studies on the association between elevated NSW and cancer-related mortality have produced contradicting results.…”

Sleep Loss and Circadian Rhythm Disruption in the Intensive Care Unit

“…33 This internal desynchronization in part explains why long-term night-shift workers have increased incidence of cardiovascular disease, metabolic syndrome, elevated inflammatory markers, and, in women, elevated cancer risk. [34][35][36][37] Thus, it follows that circadian disruptions and related molecular changes have an important bearing on the patient's ICU experience and outcomes.…”