There is no standard definition of shift work universally, and no validated report of complete biological adjustment to shift work in workers. Similarly, the evidence for shift work tolerance is ...limited due to a small number of studies and a narrow range of outcome measures. This paper discusses evidence to date regarding individual differences in shift work tolerance and highlights areas for future research and recommendations for workplace practice. The few factors that are consistently associated with perceived or actual shift work tolerance are young age, low scores of morningness or being a late chronotype, low scores of languidity and neuroticism, high scores on extraversion, internal locus of control and flexibility and male sex. An important first step is to differentiate between factors that are potentially modifiable, such as those that are determined by lifestyle choices, and those factors specific to the working time arrangement. Identifying determinants of shift work tolerance and the ability to adjust to shift work, whether they are innate and/or acquired mechanisms, is important so workers who are less likely to tolerate shift work well can be self-identified and supported with appropriate harm/risk minimization strategies. This paper also identifies important areas for future research with the goal of increasing the evidence base on which we can develop evidence-based harm mitigation strategies for shift workers.
Night work has emerged as a risk factor for many chronic diseases, including obesity, diabetes, and cardiovascular disease. While night work is linked to a number of cardiometabolic indices, few ...studies have explored how different parameters, such as cumulative night work and intensity of night work, may influence cardiometabolic risk. Fewer studies have also explored the relationship while considering chronotype, a potential modifier between shift-induced circadian disruption and cardiometabolic outcomes. The main objective is to determine the association between night work parameters and cardiometabolic risk factors. The secondary objective is to assess how the association between night work parameters and cardiometabolic risk factors differs by chronotype. A cross-sectional study was conducted with 325 full- and part-time female hospital employees (168 rotating night workers, 157 day workers). Night work status, cumulative night work duration, and night work intensity were determined through self-report, and cardiometabolic risk factors were assessed through clinical exams. Chronotype was determined using the Munich Chronotype Questionniare (MCTQ). Multiple linear regression was used to examine the association between night work parameters and cardiometabolic risk factors. Current night work, cumulative night work, and night work intensity are associated with a number of cardiometabolic indices, including higher waist circumference, body mass index, fasting glucose, blood pressure, and cardiometabolic risk score. When stratified by chronotype, night work parameters are associated with a number of cardiometabolic risk factors in the evening-oriented chronotype subgroup. There is no difference in cardiometabolic risk factors in morning-oriented chronotypes when comparing night work parameters, with the exception of LDL cholesterol. These results suggest that night work parameters are associated with cardiometabolic risk, and night workers with an evening-oriented chronotype may be more susceptible to the adverse cardiometabolic impacts of night work. Future studies should consider chronotype when examining the relationship between night work and cardiometabolic risk.
ObjectivesThe main objective was to determine whether sleep duration on work shifts mediates the relationship between a current alternating day and night shift work schedule and metabolic syndrome ...among female hospital employees. The secondary objective was to assess whether cumulative lifetime shift work exposure was associated with metabolic syndrome.MethodsIn this cross-sectional study of 294 female hospital employees, sleep duration was measured with the ActiGraph GT3X+. Shift work status was determined through self-report. Investigation of the total, direct and indirect effects between shift work, sleep duration on work shifts and metabolic syndrome was conducted using regression path analysis. Logistic regression was used to determine the association between cumulative shift work exposure and metabolic syndrome.ResultsShift work is strongly associated with metabolic syndrome (ORTotal=2.72, 95% CI 1.38 to 5.36), and the relationship is attenuated when work shift sleep duration is added to the model (ORDirect=1.18, 95% CI 0.49 to 2.89). Sleep duration is an important intermediate between shift work and metabolic syndrome (ORIndirect=2.25, 95% CI 1.27 to 4.26). Cumulative shift work exposure is not associated with metabolic syndrome in this population.ConclusionsSleep duration mediates the association between a current alternating day–night shift work pattern and metabolic syndrome.
Abstract Objective The objective of this study was to provide a systematic review of peer-reviewed literature on the factors associated with HPV vaccine acceptability among adults in African ...countries. Methods A systematic search was conducted across five electronic databases: EMBASE, PsychINFO, CINAHL, Global Health and Ovid MEDLINE, to identify studies related to HPV vaccination acceptability in African countries (August 2013). The Health Belief Model was used to guide data abstraction and synthesis. Results Fourteen unique studies representing ten sub-Saharan African countries were identified, with more than half published within the last two years. Acceptability of the HPV vaccine for daughters was high (range 59–100%); however, vaccine-related awareness and knowledge were low. Perceived barriers including accessibility and cost concerns were important for acceptance, as were cues to action from healthcare providers and governments. Conclusions This review suggests that acceptability of the HPV vaccine in countries in this region will be high. Broad knowledge gaps were highlighted regarding HPV and cervical cancer and these should be addressed. Education on the vaccine's effectiveness and reducing perceived barriers to vaccination would also be useful. Public endorsement by governments and healthcare providers will likely also increase acceptance.
Night shift work has been suspected to increase breast cancer risk but epidemiological studies have been inconsistent due to heterogeneous assessment of exposure to night work. To overcome this ...limitation, we pooled data of five population-based case-control studies from Australia, Canada, France, Germany, and Spain into a single harmonized dataset using a common definition of night work including 6093 breast cancer cases and 6933 population controls. The odds ratio for breast cancer in women who ever worked at night for at least 3 h between midnight and 5 a.m. as compared to never night workers was 1.12 (95% CI 1.00-1.25). Among pre-menopausal women, this odds ratio was 1.26 1.06-1.51, increasing to 1.36 1.07-1.74 for night shifts ≥ 10 h, 1.80 1.20-2.71 for work ≥ 3 nights/week, and 2.55 1.03-6.30 for both duration of night work ≥ 10 years and exposure intensity ≥ 3 nights/week. Breast cancer risk in pre-menopausal women was higher in current or recent night workers (OR = 1.41 1.06-1.88) than in those who had stopped night work more than 2 years ago. Breast cancer in post-menopausal women was not associated with night work whatever the exposure metric. The increase in risk was restricted to ER+ tumors, particularly those who were both ER+ and HER2+ . These results support the hypothesis that night shift work increases the risk of breast cancer in pre-menopausal women, particularly those with high intensity and long duration of exposure. Risk difference between pre- and post-menopausal women deserves further scrutiny.
Summary
Sleep disturbance is common among shift workers, and may be an important factor in the effect of shift work on chronic disease development. In this cross‐sectional study, we described sleep ...patterns of 294 female hospital workers (142 alternating day–night shift workers, 152 day workers) and determined associations between shift work and sleep duration. Rest–activity cycles were recorded with the ActiGraph GT3X+ for 1 week. Analyses were stratified by chronotype of shift workers. Using all study days to calculate average sleep duration, shift workers slept approximately 13 min less than day workers during main sleep periods, while 24‐h sleep duration did not differ between day workers and shift workers. Results from age‐adjusted models demonstrated that all shift workers, regardless of chronotype, slept 20–30 min less than day workers on day shifts during main and total sleep. Early and intermediate chronotypes working night shifts slept between 114 and 125 min less than day workers, both with regard to the main sleep episode and 24‐h sleep duration, while the difference was less pronounced among late chronotypes. When sleep duration on free days was compared between shift workers and day workers, only shift workers with late chronotypes slept less, by approximately 50 min, than day workers during main sleep. Results from this study demonstrate how an alternating day–night shift work schedule impacts sleep negatively among female hospital workers, and the importance of considering chronotype in sleep research among shift workers.
Purpose
Polycyclic aromatic hydrocarbons (PAHs) are a group of environmental pollutants associated with multiple cancers, including female breast cancer. Several xenobiotic metabolism genes (XMGs), ...including the CYP450 family, play an important role in activating and detoxifying PAHs, and variations in the activity of the enzymes they encode can impact this process. This study aims to examine the association between XMGs and breast cancer, and to assess whether these variants modify the effects of PAH exposure on breast cancer risk.
Methods
In a case–control study in Vancouver, British Columbia, and Kingston, Ontario, 1037 breast cancer cases and 1046 controls had DNA extracted from blood or saliva and genotyped for 138 single nucleotide polymorphisms (SNPs) and tagSNPs in 27 candidate XMGs. Occupational PAH exposure was assessed using a measurement-based job-exposure matrix.
Results
An association between genetic variants and breast cancer was observed among six XMGs, including increased risk among the minor allele carriers of
AKR1C3
variant rs12387 (OR 2.71, 95% CI 1.42–5.19) and
AKR1C4
variant rs381267 (OR 2.50, 95% CI 1.23–5.07). Heterogeneous effects of occupational PAH exposure were observed among carriers of
AKR1C
3/4
variants, as well as the
PTGS2
variant rs5275.
Conclusion
Our findings support an association between SNPs of XMGs and female breast cancer, including novel genetic variants that modify the toxicity of PAH exposure. These results highlight the interplay between genetic and environmental factors, which can be helpful in understanding the modifiable risks of breast cancer and its complex etiology.
Night shift work is associated with increased breast cancer risk, but the molecular mechanisms are not well-understood. The objective of this study was to explore the relationship between night shift ...work parameters (current status, duration/years, and intensity) and methylation in circadian genes as a potential mechanism underlying the carcinogenic effects of night shift work. A cross-sectional study was conducted among 74 female healthcare employees (n = 38 day workers, n = 36 night shift workers). The Illumina Infinium MethylationEPIC beadchip was applied to DNA extracted from blood samples to measure methylation using a candidate gene approach at 1150 CpG loci across 22 circadian genes. Linear regression models were used to examine the association between night shift work parameters and continuous methylation measurements (β-values) for each CpG site. The false-discovery rate (q = 0.2) was used to account for multiple comparisons. Compared to day workers, current night shift workers demonstrated hypermethylation in the 5ʹUTR region of CSNK1E (q = 0.15). Individuals that worked night shifts for ≥10 years exhibited hypomethylation in the gene body of NR1D1 (q = 0.08) compared to those that worked <10 years. Hypermethylation in the gene body of ARNTL was also apparent in those who worked ≥3 consecutive night shifts a week (q = 0.18). These findings suggest that night shift work is associated with differential methylation in core circadian genes, including CSNK1E, NR1D1 and ARNTL. Future, larger-scale studies with long-term follow-up and detailed night shift work assessment are needed to confirm and expand on these findings.
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