Years Of Shift Work Research Articles

Relationship of shift work with liver enzyme abnormalities and nonalcoholic fatty liver disease: A retrospective cohort study of Thai workers in Bangkok, Thailand

Shift work, particularly night shift work, has several detrimental health outcomes. This retrospective study investigated the associations of shift work with the incidence rates of liver enzyme abnormalities and nonalcoholic fatty liver disease (NAFLD) using the annual health check-up database between 2009 and 2016 and self-administered questionnaires from two large organizations in Thailand. Among 10,205 participants, 3620 eligible participants, classified into three subgroups by their shift work status, were followed up until abnormal liver outcomes were observed. The incidence rate of abnormal outcomes was calculated, and Cox proportional hazard models were used to assess the associations. Current shift work was not associated with abnormal liver outcomes, including elevated alanine aminotransferase and aspartate aminotransferase levels, elevated lipid accumulation product (e-LAP), and elevated hepatic steatosis index (e-HSI). However, when the frequencies and duration of shift work were investigated, the duration of shift work was associated with NAFLD outcomes. Healthcare personnel with 10–20 years of shift work experience had a higher risk of e-LAP (adjusted hazard ratio [HR] = 1.31, 95% confidence interval [CI] = 1.04–1.65), while workers with more than 20 years of shift work had a lower risk of e-LAP (adjusted HR = 0.77, 95% CI–0.62–0.97). Nonhealthcare shift workers with fewer than 10 years of work exposure had a higher risk of e-HSI (adjusted HR = 4.30, 95% CI = 1.28–14.47). In summary, the shift work status was not associated with liver abnormalities, but the duration of shift work was associated with NAFLD.

Arterial hypertension in rotating shift workers: The role of hypertriglyceridemic waist and hypertriglyceridemic waist-to-height ratio phenotypes

To examine the association of arterial hypertension and the hypertriglyceridemic waist phenotype (HWP) and hypertriglyceridemic waist-to-height phenotype (HWHP). This cross-sectional study was conducted with 1422 male rotating shift workers in Brazil. The HWP was defined as having a waist circumference ≥94cm and serum triglycerides ≥150mg/dL, whereas the HWHP was determined by having a waist-to-height ratio ≥0.5 and serum triglycerides ≥150mg/dL. To provide a characterization of the sample, data were presented in both absolute and relative values, and Pearson's chi-square test was employed. To investigate the potential association between arterial hypertension and the presence of HWP or HWHP, multivariate logistic regression was conducted, accounting for sociodemographic, behavioral, and clinical variables. Furthermore, we conducted a stratified multivariate logistic regression analysis, considering the duration of shift work, to assess whether the results remained consistent depending on the length of work experience in shifts. A noteworthy association was observed between arterial hypertension and both HWP and HWHP, with HWHP exhibiting a stronger association with the disease. Furthermore, a positive association between arterial hypertension and these phenotypes was identified in workers with five or more years of shift work. We recommend the utilization of HWHP as a screening tool, as it indicates a stronger association with arterial hypertension compared to HWP. Additionally, the duration of time spent working in shifts emerged as a significant factor influencing the presence of these phenotypes.

Rotating shift work time is directly associated with excess body adiposity.

To analyze the association between changes in body adiposity andlength of service on a schedule of rotating shifts. The study was a cross-sectional investigation conducted during the years 2012, 2015, and 2018, involving individuals engaged in rotating shifts at a company involved in iron ore extraction situated within the Iron Quadrangle region of Minas Gerais and the southeastern region of Pará, Brazil. Sociodemographic and behavioral datawere collected along withanthropometric parameters in order to calculatebody mass index (BMI) and the waist-to-height ratio (WHtR). For data analysis, a multivariate logistic regression was employed to explore potential associations between indicators of body adiposity and the duration of shift work, employing a hierarchical determination model. The findings showed that in the multivariate model, controlling for confounding factors, workers with 5 to 10, 10 to 15, and more than 15 years of shift work had 41 to 96% greater odds of being overweight (BMI > 25.0 kg/m2), 71 to 82% of having altered neck circumference (> 40 cm), 33 to 120% of altered WC (>102 cm), and 57 to 214% of having altered WHtR (> 0.5 cm). The findings suggest thattime spent inwork has a significant effect on anthropometric indicators of body adiposity, especially if the worker has a previously established comorbidity such as dyslipidemia or hypertension and is frequently exposed to night work.

The Effect of Commencing Rotating Shift Work on Diet and Body Composition Changes in Graduate Paramedics: A Longitudinal Mixed Methods Study

Objectives: Diet quality often changes as shift workers adjust to atypical work schedules, however, limited research exists examining the early effects of starting rotating shift work on diet and body composition. This study explored dietary behavior changes occurring in graduate paramedics during the first year of exposure to rotating shift work, and investigated dietary intake, diet quality and anthropometric changes over two years. Methods: Participants from a graduate paramedic cohort in Melbourne, Australia were approached after two years of shift work for study inclusion. Using a mixed method study approach, the qualitative component comprised individual in-depth interviews to explore perceived dietary behavior changes experienced over the first year of shift work. Interview transcripts were thematically analyzed and guided by the COM-B model (capability, opportunity, motivation, and behavior) and theoretical domains framework (TDF). Diet quality and dietary intake were quantitatively assessed by the Australian Eating SurveyTM at baseline, one year, and two years, along with body weight, waist circumference, and body mass index (BMI) to monitor changes. Results: Eighteen participants were included in the study. From the interviews, participants reported: 1. food choices are driven by wanting to fit in with coworker food habits, 2. food choices and mealtimes are unpredictable and 3. paramedics try to make healthy food choices but give in to less healthy options. While daily energy intake and diet quality scores did not differ in the first two years of shift work, daily energy from takeaway foods significantly increased (mean difference (MD): 2.96% EI; 95% CI: 0.44 − 5.48; p = 0.017) and increases in weight (MD: 2.96 kg; 95% CI: 0.89-5.04; p = 0.003), BMI (MD: 1.07 kg/m2; 95% CI: 0.26 – 1.87; p = 0.006) and waist circumference (MD: 5.07 cm; 95% CI: 1.25-8.89; p = 0.006) were also evident at two years. Conclusions: This study contributes new information on dietary changes and the current early trajectory of unintentional weight gain and takeaway reliance occurring within a graduate paramedic cohort over two years of shift work. To reduce the unintended metabolic consequences commonly observed with rotating shift schedules, workplaces could improve access to healthier food options and enable behavioral support/education to address nutrition-related health risks.

Lifestyle Factors in the Association of Shift Work and Depression and Anxiety

Shift work may lead to adverse health outcomes. Whether shift work is associated with depression and anxiety, and to what extent lifestyle mediates the associations, remains unknown. To explore the associations of shift work, its type, frequency, and working years with anxiety and depression and to examine the potential mediating role of lifestyles. This cohort study included 175 543 employed or self-employed workers who participated in the UK Biobank baseline survey (2006-2010). Data analysis was conducted from November 2022 to January 2023. Employment and shift work status information was obtained from baseline. Lifestyles included smoking, physical activity, alcohol consumption, dietary characteristics, sleep duration, sedentary time, and body mass index (BMI). Depression and anxiety were identified based on electronic health records. Cox proportional hazard regression models were used to calculate the association of shift work with anxiety and depression, and cause mediation analyses we used to test the mediating role of lifestyle factors in this association. Of the 175 543 included participants (mean [SD] age, 52.6 [7.1] years; 88 290 men [50.3%]; 167 495 White participants [95.4%]), 27 637 participants (16.2%) reported shift work. During a median (IQR) follow-up of 9.06 (8.35-9.75) years, 3956 workers (2.3%) developed depression and 2838 (1.7%) developed anxiety. In the fully adjusted model, individuals who reported engaging in shift work, or shift workers, had a higher risk of depression (HR, 1.22; 95% CI, 1.12-1.33; P < .001) and anxiety (HR, 1.16; 95% CI, 1.04-1.28; P < .001), and the risk was positively associated with shift frequency. Among shift workers, there was no significant difference between night shifts and nonnight shifts. In the dose-association analyses, years of shift work were negatively associated with the risk of depression and anxiety. Smoking, sedentary time, BMI, and sleep duration were identified as the main potentially modifiable mediators. These mediators together explained 31.3% of the association between shift work and depression and 21.2% of the association between shift work and anxiety. In this cohort study, shift work was significantly associated with a higher risk of depression and anxiety, and lifestyle factors partially mediated the associations. These findings not only support that shift work should be considered an occupational hazard, but also provide evidence for the urgent need for the development of public health interventions that promote healthy lifestyles aimed at improving the mental health of shift workers.

The impact of shift work and sleep deficiency on health

Shift work refers to work that takes place at different hours, including at night. It is estimated that 15% to 20% of the working population works in shift work, particularly in the healthcare, energy, communication systems, public safety, and hospitality industries. Research indicates that shift work, particularly night work, can lead to health problems such as fatigue, exposure to harmful work environments, increased risk of workplace accidents, and sleep disorders. Night work is also associated with increased risk of hypertension, nervous system dysfunction, cardiovascular dysfunction. Those working at night are also more prone to hormonal disorders, digestive disorders, lowered immunity, and cancer. Sleep-wake cycle disorders, such as excessive sleepiness during waking hours and insomnia at night, are symptoms of shift work intolerance syndrome, which can occur after several months or years of shift work. It is estimated that over 20% of shift workers suffer from sleep-wake cycle disorders, and various factors such as chronotype, age, gender, family and social obligations, medications, medical and psychiatric conditions, and shift work experience can impact tolerance of shift work. The treatment of sleep and wake disorders related to shift work includes planning for main sleep and supplementary naps, appropriate exposure to light, treatment with melatonin, taking sleeping and psychostimulant medications.

Sleep, chronotype, and quality of life of shift duty workers in tertiary care center of Saurashtra

Abstract Background: Insomnia in shift work has been associated with impairment in health and social life and poor quality of life among shift workers. Aims and Objective: The study aimed to assess insomnia, chronotype, and quality of life in nursing shift duty workers and to find an association among insomnia, chronotype, and quality of life in nursing shift duty workers of a tertiary care center in Saurashtra. Materials and Methods: A cross-sectional study was carried out among 300 nursing shift duty workers. Consented participants with at least one-night duty per week were included in our study. A semistructured proforma containing basic demographic details and scales such as ‘Insomnia Severity Index’ (ISI), ‘Composite Scale of Morningness,’ and ‘world health organization quality of life’ were distributed among all participants. Associations were examined by using t test and Chi-square test. Results: The prevalence of insomnia was 42.66% in this study. A total of 27.33% of participants were having mild insomnia, whereas 15.33% were having moderate-to-severe insomnia. Insomnia severity was statistically significantly associated with needle stick injury (p = 0.003) and years of shift work (0.031). Insomnia severity had been significantly associated with the chronotype of participants, negative but statistically significant correlation was found between the ISI score and mean score of all four domains of world health organization quality of life. Conclusion: Insomnia in shift work has been associated with evening chronotype and poorer quality of life of shift workers. Therefore, the management of insomnia is important for a better quality of life for shift workers. Participants with insomnia are more prone to needle stick injury during work.

Rotating night shift work, sleep and thyroid cancer risk in the Nurses’ Health Study 2

Background and aim Thyroid cancer is the most common endocrine malignancy with rising incidence worldwide. We prospectively evaluated whether rotating night shift work and sleep disturbances are associated with incident thyroid cancer risk in the Nurses’ Health Study 2 (NHS2). Methods We assessed rotating night shift work (&amp;#x2265;3 nights/month) history (cumulative number of years) at baseline and throughout follow-up (1989-2015) and sleep duration and sleep difficulty in 2001. Cox proportional hazard models, adjusted for potential confounders were used to calculate thyroid cancer hazard ratios (HR) and 95% confidence intervals (CI) for shift work history (0.1-4.9yrs, 5-9.9yrs, 10+yrs), sleep duration (&amp;#x2264;5, 6, 7, 8, &amp;#x2265;9hours) and difficulty falling or staying asleep (little or none of the time, sometimes, most or all of the time). We further stratified the analyses of night shift work by sleep characteristics. Results We identified 588 incident cases among 114,534 women. We observed no association between night shift work history and thyroid cáncer risk (1-4.9 years: HR 1.19, 95% CI 0.98, 1.44; 5-9.9 years: HR 1.13 95% CI 0.86, 1.48; &amp;#x2265;10 years: HR 1.10, 95% CI 0.78, 1.54; Ptrend=0.55). Sleep difficulty was suggestively associated with higher incidence of thyroid cancer when reported sometimes (HR 1.26, 95% CI 0.95, 1.67) and most or all the time (HR 1.35, 95% CI 1.00, 1.81; Ptrend=0.03), compared to little or none of the time. Participants with &amp;#x3e;10 years of night shift work and &amp;#x2264;6 hours of sleep had a 2-fold increase in thyroid cancer risk (HR 2.23; 95%CI, 1.08-4.06). Shift workers with &amp;#x3c;5 years of shift work and frequent sleep difficulty had an increased risk of thyroid cancer (HR 1.95; 95% CI 1.03, 3.67). Conclusion We found evidence that rotating night workers with frequent sleep difficulty or short sleep had an increased risk of thyroid cáncer. Keywords night work, thyroid cancer

Multimodal investigation of the association between shift work and the brain in a population-based sample of older adults

Neuropsychological studies reported that shift workers show reduced cognitive performance and circadian dysfunctions which may impact structural and functional brain networks. Here we tested the hypothesis whether night shift work is associated with resting-state functional connectivity (RSFC), cortical thickness and gray matter volume in participants of the 1000BRAINS study for whom information on night shift work and imaging data were available. 13 PRESENT and 89 FORMER night shift workers as well as 430 control participants who had never worked in shift (NEVER) met these criteria and were included in our study. No associations between night shift work, three graph-theoretical measures of RSFC of 7 functional brain networks and brain morphology were found after multiple comparison correction. Preceding multiple comparison correction, our results hinted at an association between more years of shift work and higher segregation of the visual network in PRESENT shift workers and between shift work experience and lower gray matter volume of the left thalamus. Extensive neuropsychological investigations supplementing objective imaging methodology did not reveal an association between night shift work and cognition after multiple comparison correction. Our pilot study suggests that night shift work does not elicit general alterations in brain networks and affects the brain only to a limited extent. These results now need to be corroborated in studies with larger numbers of participants.

The association between shift work and lower extremity osteoarthritis among retired workers

Objective: To investigate the association between shift work and the risk of lower extremity osteoarthritis. Methods: The study population came from the Dongfeng-Tongji cohort established in 2008. In September 2008, the Dongfeng Motor Company in Hubei Province was to recruit all retired workers who voluntarily participated in the survey as the research objects. During the follow-up conducted from April to October 2013, a total of 14 438 retired workers, i.e. all of the participants who underwent physical examination were investigated about demographic characteristics, lifestyles, occupation history, and lower extremity joint-related medical history, and additionally completed lower extremity joint examinations. After excluding individuals with missing data regarding lower extremity osteoarthritis, with the history of lower extremity joint trauma, or with history of rheumatoid arthritis (N=532), data from 13 906 participants was analyzed in the study. Multivariate logistic regression models were used to estimate the association between shift work and lower extremity osteoarthritis. After stratified by the duration of shift work, multivariate logistic regression models were used to analyze the relationship between the duration after leaving from shift work and lower extremity osteoarthritis. Results: Finally, a total of 13 906 retired employees included 7 560 (54.4%) females with a mean age of 64.74 (standard deviation 8.23) years old. 5 537 (39.8%) workers had ever engaged in shift work, including 2 004 (14.4%) workers with 1-9 years of shift work and 3 533 (25.4%) workers with ≥ 10 years of shift work. The prevalence of lower extremity osteoarthritis was 7.0%, while the prevalence of knee osteoarthritis and hip osteoarthritis were 6.7% and 0.7%, respectively. Compared with daytime workers, shift workers showed a 22% increase in the risk of lower extremity osteoarthritis (OR=1.22, 95%CI:1.06-1.40). Each 5-year increase in the duration of shift work was associated with a 4% increase in the risk of lower extremity osteoarthritis (OR=1.04, 95%CI:1.01-1.08). With the extension of the duration after leaving from shift work, the risk of lower extremity osteoarthritis decreased. Similar relationships were found between shift work and the risk of knee osteoarthritis, as well as hip osteoarthritis. Conclusion: Shift work was associated with the increased risk of lower extremity osteoarthritis.

Shift work, and burnout and distress among 7798 blue-collar workers

ObjectiveThis study aimed to investigate the association between shift work, and burnout and distress, and differences by degree of satisfaction with shift schedule and its impact on private life.MethodsPopulation 4275 non-shift factory workers and 3523 rotating 5-shift workers. Workers participated between 2009 and 2016 one to three times in the companies’ periodical occupational health checks. Burnout was measured using the distance, exhaustion and competence subscales of the Dutch Maslach Burnout Inventory and distress by the subscale of the Four-Dimensional Symptom Questionnaire (scale: 0–100). Multiple-adjusted linear mixed models were used to assess between- and within-subject associations between shift work and outcomes, and differences by age, years of shift work, and satisfaction with and impact of shift schedule.ResultsShift work was significantly associated with lower scores on burnout distance (B − 1.0, 95% − 1.8 to 0.3), and among those aged < 48 years with burnout exhaustion (range B − 1.3 to − 1.6). However, the effect sizes were small. Compared to non-shift workers, shift workers dissatisfied with their schedule and those experiencing a high impact on private life had significantly higher burnout (range B 1.7–6.3) and distress levels (range B 4.9–6.1). In contrast, satisfied shift workers and those experiencing a low impact of shift schedule had lower burnout (range B − 0.2 to − 2.2) and no difference in distress levels (P ≥ 0.05). No clear pattern by years of shift work was observed.ConclusionsShift work was associated with burnout and distress in those who were dissatisfied with or who had perceived high impact on the private life of their shift schedule.

A meta-analysis of cohort studies including dose-response relationship between shift work and the risk of diabetes mellitus.

Previous reviews have suggested that shift work is associated with an increased risk of diabetes mellitus (DM); however, the results should be interpreted with caution due to differences in study designs and non-comprehensive literature searches. In addition, the quantitative dose-response relationship between years of shift work and DM risk is still unknown. We aimed to conduct an updated meta-analysis with cohort studies and to evaluate the relationship between the duration of shift work and the risk of DM in a dose-dependent manner. The PubMed and Web of Science databases were searched through 15 August 2019, and multivariate-adjusted relative risks (RRs) were pooled using random-effects models. Restricted cubic spline analysis with three knots was used to explore the relationship of years of shift work and risk of DM. Twelve cohort studies with 28 independent reports involving 244,266 participants and 15,906 DM cases were included. The summarized adjusted RR for the relationship between shift work and DM risk was 1.14 (95% CI 1.10 to 1.19; I2 = 38.9%, P = 0.028). The summary RR of a 5-year increase in shift work was 1.07 (95% CI 1.04 to 1.09), without heterogeneity (I2= 0.0%, P = 0.829) for the female population. Shift work is associated with an increased risk of DM, and a strong and highly significant linear dose-response relationship between the duration of shift work and the risk of DM in women was observed. Further studies are needed to confirm the results, establish causality and elucidate the underlying mechanisms.

Exploring the associations between shift work disorder, depression, anxiety and sick leave taken amongst nurses.

This study aimed to evaluate the association between shift work disorder and mental health in hospital-based nurses. Staff completed an online survey comprising demographic questions, the Shift Work Disorder Questionnaire, Patient Health-9 and the General Anxiety Disorder-7 scale. Sick leave data were collected from archival records from the Human Resources Department. Two hundred and two nurses (95% female; age M=35.28years±SD=12) participated (42% of eligible staff). Those at high risk of shift work disorder had higher depression (M=7.54±SD=4.28 vs. M=3.78±SD=3.24; p<0.001) and anxiety (M=5.66±SD=3.82 vs. M=2.83±SD=3.33, p<0.001) compared to those at low risk. Linear regression models showed that being at high risk of shift work disorder was the most significant predictor of depression, explaining 18.8% of the variance in depression (R2 =0.188, adjusted R2 =0.184, F(1, 200)=46.20, p<0.001). Shift work disorder combined with the number of night shifts and alcoholic drinks on non-work days accounted for 49.7% of the variance in anxiety scores (R2 =0.497, adjusted R2 =0.453, F(3, 35)=11.51, p<0.001). Mean sick leave in those with high risk of shift work disorder was 136.17hr (SD=113.11) versus 103.98hr (SD=94.46) in others (p=0.057). Depression and years of shift work accounted for 18.9% of the variance in sick leave taken (R2 =0.189, adjusted R2 =0.180, F(2, 175)=20.36, p<0.001). Shift work disorder is strongly associated with depression and anxiety, providing a potential target to improve mental health in shift workers. Depression, in turn, is a significant contributing factor to sick leave.

Shift Work Patterns, Chronotype, and Epithelial Ovarian Cancer Risk.

Shift work causing circadian disruption is classified as a "probable carcinogen" and may contribute to the pathogenesis of hormone-sensitive cancers. This study investigated shift work exposure in relation to epithelial ovarian cancer (EOC) risk. In a population-based case-control study with 496 EOC cases and 906 controls, lifetime occupational histories were collected and used to calculate cumulative years of shift work exposure, average number of night shifts per month, and average number of consecutive night shifts per month. ORs and 95% confidence intervals (CI) for associations with EOC risk were estimated using logistic regression. Associations were also examined according to chronotype and menopausal status. More than half of the cases (53.4%) and controls (51.7%) worked evening and/or night shifts. There was no clear pattern of increasing EOC risk with increasing years of shift work; the adjusted OR of EOC comparing the highest shift work category versus never working shift work was 1.20 (95% CI, 0.89-1.63). This association was more pronounced among those self-identified as having a "morning" chronotype (OR, 1.64; 95% CI, 1.01-2.65). Associations did not greatly differ by menopausal status. These results do not strongly demonstrate a relationship between shift work and EOC risk. This study collected detailed shift work information and examined shift work patterns according to shift times and schedules. The findings highlight that chronotype should be considered in studies of shift work as an exposure.

Association between shift work and hyperhomocysteinemia in male workers.

BackgroundShift work is associated with a higher risk of cardiovascular diseases. Here, we sought to assess the relationship between shift work and plasma homocysteine levels. Determining the correlations between shift work and homocysteine levels may provide a better understanding of the mechanisms underlying cardiovascular diseases.MethodsThis study was performed using data from routine health examinations of steel workers in 2017. In total, 431 male workers (70 daytime workers and 361 shift workers) employed on a rolling departure schedule were recruited. Plasma homocysteine levels > 15 μmol/L were considered elevated. The χ2, analysis of variance, and multiple logistic regression analyses were used to examine the association between shift work and plasma homocysteine levels.ResultsIn comparison to daytime workers, the odds ratio (OR) of hyperhomocysteinemia in individuals with < 10 years of shift work was 1.14 (95% confidence interval [CI]: 0.64–2.03), compared to 2.01 (95% CI: 1.14–3.54) for workers with ≥ 10 years of experience. After adjusting for confounding variables, the adjusted OR for shift workers with < 10 years of experience was 0.95 (95% CI: 0.50–1.80), compared to 2.00 (95% CI: 1.07–3.74) for workers with ≥ 10 years of experience.ConclusionsThe risk of hyperhomocysteinemia was significantly higher in shift workers compared to those working normal daytime hours, particularly among long-term shift workers.

Shift work and risk of incident dementia: a study of two population-based cohorts

This study aimed to investigate the association between shift work and incident dementia in two population-based cohorts from the Swedish Twin Registry (STR). The STR-1973 sample included 13,283 participants born 1926–1943 who received a mailed questionnaire in 1973 that asked about status (ever/never) and duration (years) of shift work employment. The Screening Across the Lifespan Twin (SALT) sample included 41,199 participants born 1900–1958 who participated in a telephone interview in 1998–2002 that asked about night work status and duration. Dementia diagnoses came from Swedish patient registers. Cox proportional-hazards regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI). Potential confounders such as age, sex, education, diabetes, cardiovascular disease and stroke were included in adjusted models. In genotyped subsamples (n = 2977 in STR-1973; n = 10,366 in SALT), APOE ε4 status was considered in models. A total of 983 (7.4%) and 1979 (4.8%) dementia cases were identified after a median of 41.2 and 14.1 years follow-up in the STR-1973 and SALT sample, respectively. Ever shift work (HR 1.36, 95% CI 1.15–1.60) and night work (HR 1.12, 95% CI 1.01–1.23) were associated with higher dementia incidence. Modest dose-response associations were observed, where longer duration shift work and night work predicted increased dementia risk. Among APOE ε4 carriers, individuals exposed to ≥ 20 years of shift work and night work had increased dementia risk compared to day workers. Findings indicate that shift work, including night shift work, compared to non-shift jobs is associated with increased dementia incidence. Confirmation of findings is needed.

Shift work and risk of cardiovascular disease morbidity and mortality: A dose–response meta-analysis of cohort studies

Background Previous studies have suggested that shift work is associated with a higher risk of cardiovascular disease. However, the quantitative dose-response relationship between duration of shift work and cardiovascular disease risk is still unknown. We aimed to evaluate the dose-response association between duration of shift work and risk of cardiovascular disease morbidity and mortality. Design A systematic review and meta-analysis. Methods PubMed and Embase were searched from inception to 1 December 2017. Prospective cohort studies that reported the associations between duration of shift work and cardiovascular disease risk with at least three categories were included. Data were pooled by using fixed or random effect models. The continuous dose-response associations were assessed by using fixed effect restricted cubic splines with four knots. Results Five prospective cohort studies with 10 reports were included. No evidence of a curvilinear association was observed between duration of shift work and risk of cardiovascular disease, similar findings were observed in cardiovascular disease morbidity and mortality. The summary relative risk (RR) of an increase of 5 years of shift work was 1.05 (1.04-1.07) with moderate heterogeneity ( P = 0.142, I2 = 33.2%) for cardiovascular disease, 1.06 (1.04-1.08) with low heterogeneity ( P = 0.279, I2 = 21.7%) for cardiovascular disease morbidity, and 1.04 (1.02-1.06) with moderate heterogeneity ( P = 0.135, I2 = 38.5%) for cardiovascular disease mortality, respectively. Conclusions Shift work could probably increase the risk of cardiovascular disease and cardiovascular disease mortality in a dose-response way. These findings could have implications for guideline recommendations regarding the risk related to shift schedules.

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

Objectives The aim of this review was to assess the risk of cardiovascular disease (CVD) events associated with shift work and determine if there is a dose-response relationship in this association. Method Electronic databases (PubMed, Scopus, and Web of Science) were searched for cohort or case-control control study designs in any population, reporting exposure to shift work as the main contributing factor to estimate CVD risk. For each study, adjusted relative risk (RR) ratios and 95% confidence intervals (CI) were extracted, and used to calculate the pooled RR using random-effect models. Meta-regression analysis was conducted to explore potential heterogeneity sources. Potential non-linear dose-response relationships were examined using fractional polynomial models. Results We included 21 studies with a total of 173 010 unique participants. The majority of the studies were ranked low-to-moderate risk of bias. The risk of any CVD event was 17% higher among shift workers than day workers. The risk of coronary heart disease (CHD) morbidity was 26% higher (1.26, 95% CI 1.10-1.43, I 2= 48.0%). Sub-group analysis showed an almost 20% higher risk of CVD and CHD mortality among shift workers than those who did not work shifts (1.22, 95% CI 1.09-1.37, I 2= 0% and 1.18, 95% CI 1.06-1.32 I 2=0%; respectively). After the first five years of shift work, there was a 7.1% increase in risk of CVD events for every additional five years of exposure (95% CI 1.05-1.10). Heterogeneity of the pooled effect size (ES) estimates was high (I 2=67%), and meta-regression analysis showed that sample size explained 7.7% of this. Conclusions The association between shift work and CVD risk is non-linear and seems to appear only after the first five years of exposure. As shift work remains crucial for meeting production and service demands across many industries, policies and initiatives are needed to reduce shift workers' CVD risk.

0688 IMPACT OF CIRCADIAN MISALIGNMENT AND BMI ON GLUCOSE DYSREGULATION IN NIGHT-SHIFT WORKERS

Epidemiological studies suggests that night shift workers are at increased risk for obesity and diabetes, and simulated shift work studies in day workers have implicated circadian misalignment as a culprit for reduced glucose tolerance. However, this has not been tested in actual night shift workers. To better understand the role of circadian misalignment on glucose dysregulation, we examined glucose tolerance in a sample of fixed night shift workers. Thirty fixed night shift workers participated in this study. All subjects were given an eight-hour opportunity to sleep upon arrival at the lab, and remained under dim-light conditions for 24 hours. An oral glucose tolerance test was administered two hours after awakening. The change in glucose from fasting to one hour after glucose intake, and from fasting to two hours after glucose intake were measured. Melatonin was also assayed via hourly salivary samples, and circadian phase was indexed using the dim light melatonin onset (DLMO). Analyses included years of night shift work as a covariate. Partial correlations controlling for years of shift work indicated that DLMO was not significantly associated with change in glucose tolerance at one-hour, r(27) = .07, p>.05, or at two-hour, r(27) = -.24, p>.05. However, DLMO was significantly associated with glucose tolerance when accounting for weight. Specifically, overweight shift workers (BMI ≥ 26) with earlier DLMOs showed lower glucose tolerance at the two-hour time point, r (15) = -.46, p<.05, compared to subjects with healthy weight, r (9) = .06, p>.05. Results suggest that circadian misalignment alone may not be a significant predictor for glucose dysregulation, but instead may interact with other risk factors for diabetes, such as weight. Thus, increased risk for diabetes in night shift workers should not be generalized, but rather considered only when circadian disturbance is paired with pre-existing risk factors. Our project was funded by TEVA pharmaceuticals.

Non-occupational physical activity levels of shift workers compared with non-shift workers

ObjectivesLack of physical activity (PA) has been hypothesised as an underlying mechanism in the adverse health effects of shift work. Therefore, our aim was to compare non-occupational PA levels between...