Duration Of Shift Work Research Articles

Shift work and the relationship with metabolic syndrome in Chinese aged workers.

BackgroundShift work is indicated to be associated with adverse metabolic disorders. However, potential effects of shift work on metabolic syndrome (MetS) and its components have not been well established.MethodsIn total, 26,382 workers from Dongfeng-Tongji Cohort were included in this study. Information on shift work history was gathered through questionnaires and metabolic traits were measured. Logistic regression models were used to calculate the odds ratio (OR) and 95% confidence interval (CI) for long-term shift work related with MetS and each component, respectively. Further stratification analysis was performed to detect the differences on MetS between female and male shift workers.ResultsLong-term shift work was associated with MetS without adjusting for any confounders. Compared with the group of non-shift work, the multivariate-adjusted ORs (95%CI) of MetS associated with 1–10, 11−20, and ≥20y of shift work were 1.05 (0.95−1.16), 1.14 (1.03−1.26), 1.16 (1.01−1.31), respectively. In female workers, we found a dose-response relationship that every 10 years increase in shift work was associated with a 10% (95% CI: 1%−20%) elevated OR of MetS, while no significant dose-response trend was found among male workers. Furthermore, shift work duration was significantly associated with ORs of high blood pressure (1.07, 1.01−1.13), long waist circumference (1.10, 1.01−1.20) and high glucose levels (1.09, 1.04−1.15). No significant association was observed between shift work and low HDL cholesterol) and raised triglyceride levels.ConclusionsLong-term shift work was associated with metabolic syndrome and the association might differ by gender in retired workers. Applicable intervention strategies are needed for prevention of metabolic disorders for shift workers.

Night-shift work and incident diabetes among African-American women.

The aim of this study was to assess shift work in relation to incident type 2 diabetes in African-American women. In the Black Women's Health Study (BWHS), an ongoing prospective cohort study, we followed 28,041 participants for incident diabetes during 2005-2013. They answered questions in 2005 about having worked a night shift. We estimated HR and 95% CIs for incident diabetes using Cox proportional hazards models. The basic multivariable model included age, time period, family history of diabetes, education and neighbourhood socioeconomic status. In further models, we controlled for lifestyle factors and BMI. Over the 8 years of follow-up, there were 1,786 incident diabetes cases. Relative to never having worked the night shift, HRs (95% CI) for diabetes were 1.17 (1.04, 1.31) for 1-2 years of night-shift work, 1.23 (1.06, 1.41) for 3-9 years and 1.42 (1.19, 1.70) for ≥ 10 years (p-trend < 0.0001). The monotonic positive association between night-shift work and type 2 diabetes remained after multivariable adjustment (p-trend = 0.02). The association did not vary by obesity status, but was stronger in women aged <50 years. Long duration of shift work was associated with an increased risk of type 2 diabetes. The association was only partially explained by lifestyle factors and BMI. A better understanding of the mechanisms by which shift work may affect the risk of diabetes is needed in view of the high prevalence of shift work among workers in the USA.

교대근무자의 회복력과 수면 및 방어 특성

목 적 : 교대근무는 상당한 스트레스 상황이며 교대근무에 잘 적응하는 정도와 관련된 요인들을 아는 것은 중요하다. 본 연구에서는 교대근무 간호사들의 회복력과 관련된 수면 및 성격 관련 요인들을 조사해보고자 했다. 방 법 : 일 대학병원에서 3교대 근무를 하고 있는 간호사 95명을 대상으로 자가 설문지 조사를 시행했다. 코너-데이비드슨 회복력 척도, 병원 불안-우울 척도, 아침형-저녁형 질문지와 피츠버그 수면의 질 지수를 포함한 수면 관련 설문, 한국판 방어유형 질문지를 이용했다. 결 과 : 회복력과 유의한 상관을 보인 요소들은 근무자들의 나이, 근무 기간, offday oversleep, HAD-D 및 HAD-A 점수, DSQ의 적응적 방어유형, 자기억제적 방어유형이었다(p < 0.05). 다중회귀분석에서는 나이가 많을 수록(<TEX>${\beta}=0.34$</TEX>, p < 0.05), 우울 증상이 적을 수록(<TEX>${\beta}=-0.25$</TEX>, p < 0.05), 적응적 방어유형을 많이 사용할 수록(<TEX>${\beta}=0.45$</TEX>, p < 0.001), 자기억제적 방어유형을 적게 사용할 수록(<TEX>${\beta}=-0.19$</TEX>, p < 0.05) 회복력이 높은 것으로 나타났다. 방어기제들의 경우 체념이 적을 수록(<TEX>${\beta}=-0.20$</TEX>, p < 0.05), 승화(<TEX>${\beta}=0.19$</TEX>, p < 0.05)와 전능(<TEX>${\beta}=0.19$</TEX>, p < 0.05), 유머(<TEX>${\beta}=0.20$</TEX>, p < 0.05)를 많이 사용할 수록 회복력이 높은 것으로 나타났다. 결 론 : 본 연구에서는 일 대학병원의 3교대 근무 간호사들의 특정 방어유형 및 방어기제가 회복력과 관계된다는 것을 밝힐 수 있었다. 추후 더 많은 교대근무 간호사들을 대상으로 회복력과 관련된 수면 및 성격 관련 인자들을 밝히는 전향적 연구가 가능할 것이다. Objectives: Shift work is a stressful situation. It is important to know the factors associated with the ability to adapt to a shift work schedule. The aim of the present study was to investigate the association between sleep, as well as personality variables, and the resilience of shift work nurses. Method: Self-report questionnaires were administered to 95 nurses who worked in one national university hospital. Connor-Davidson resilience scale, hospital anxiety and depression scale, morningness-eveningness scale, Pittsburgh sleep quality index, other sleep-related questionnaires, and Korean defense style questionnaires were used. Results: Age, shift work duration, off-day oversleep, depression, anxiety, adaptive defense style, and self-suppressive defense style were significantly associated with resilience (p < 0.05). Multiple regression analysis showed that age (<TEX>${\beta}=0.34$</TEX>, p < 0.05), depression (<TEX>${\beta}=-0.25$</TEX>, p < 0.05), adaptive defense style (<TEX>${\beta}=0.45$</TEX>, p < 0.001), and self-suppressive defense style (<TEX>${\beta}=-0.19$</TEX>, p < 0.05) significantly predicted the resilience of shift work nurses. Concerning individual defense mechanisms, resignation (<TEX>${\beta}=-0.20$</TEX>, p < 0.05), sublimation (<TEX>${\beta}=0.19$</TEX>, p < 0.05), omnipotence (<TEX>${\beta}=0.19$</TEX>, p < 0.05), and humor (<TEX>${\beta}=0.20$</TEX>, p < 0.05) significantly predicted the resiliency. Conclusion: The findings indicate that a specific defense style and other mechanisms were associated with the resilience of shift work nurses. A future prospective study with more participants could further clarify the relationship between sleep-related variables, as well as personality factors, and resilience of shift work nurses.

Abstract 2181: Association of sleep duration, daytime napping, and night shift work with breast cancer risk

Abstract Sleep habit is closely related to melatonin which protect against breast cancer (BC). Sleep duration, nap habit, and shift work have been separately investigated to associate with BC risk, but the combination has not been reported. In this study, we collected all the sleep habits data from 712 women with incident invasive BC before their treatments and 742 age-matched female controls between July 2010 and January 2012 in Guangzhou, China. We found that the women with either shorter or longer sleep duration had increased BC risk compared to the women with normal sleep time of 6.1-8.9h/day [OR (95%CI: 1.62 (1.18-2.24) and 1.55 (1.14-2.10), respectively]. Night shift work also increased the risk of BC [1.36 (1.07-1.73)] and nap habits marginally associated a decreased risk [0.83 (0.66-1.04)]. Women with night shift work and longer sleep duration had an increased risk of BC [3.80 (1.99-7.26)] compared to the women with normal sleep time and no night shift work. The interaction on BC risk was significant (P for interaction=0.009). We conclude that abnormal sleep increases BC risk and longer sleep duration may not compensate the effect of night shift work on risk of BC. Table 1.Age-adjusted and multivariate-adjusted odds rations for the associations between sleep habits and breast cancer riskVariablesCases Controls OR#(95%CI)OR* (95%CI)OR^ (95%CI)(n=712) (%)(n=742)(%) Shift worknever443 (67.0)527 (73.8)1.00 (reference)1.00 (reference)1.00 (reference)ever218 (33.0)187 (26.2)1.39 (1.10-1.75)1.36 (1.07-1.73)1.34 (1.04-1.71)Napping statusnever293 (44.5)254 (37.7)1.00 (reference)1.00 (reference)1.00 (reference)ever365 (55.5)420 (62.3)0.75 (0.61-0.94)0.83 (0.66-1.04)0.83 (0.66-1.06)24-hour sleep duration≤6.0116 (17.7)85 (12.8)1.62 (1.18-2.21)1.62 (1.18-2.24)1.52 (1.10-2.11)6.1-8.9409 (62.6)485 (72.7)1.00 (reference)1.00 (reference)1.00 (reference)≥9.0129 (19.7)97 (14.5)1.58 (1.18-2.12)1.55 (1.14-2.10)1.59 (1.17-2.17)P-continuous0.6460.8830.451P-trend0.9090.9960.661OR#: Adjusted for age.OR*: Adjusted for age, education, BMI, marital status, age at menarche, menopausal status, parity, activity, breastfeeding and family history of breast cancer.OR^: Adjusted for age, education, BMI, marital status, age at menarche, menopausal status, parity, activity, breastfeeding, family history of breast cancer, and other sleep factors. Citation Format: Zefang Ren. Association of sleep duration, daytime napping, and night shift work with breast cancer risk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2181. doi:10.1158/1538-7445.AM2014-2181

Night shift work and modifiable lifestyle factors.

Night shift work has been linked to some chronic diseases. Modification of lifestyle by night work may partially contribute to the development of these diseases, nevertheless, so far epidemiological evidence is limited. The aim of the study was to explore association between night shift work and lifestyle factors using data from a cross-sectional study among blue-collar workers employed in industrial plants in Łódź, Poland. The anonymous questionnaire was self-administered among 605 employees (236 women and 369 men, aged 35 or more) - 434 individuals currently working night shifts. Distribution of the selected lifestyle related factors such as smoking, alcohol drinking, physical activity, body mass index (BMI), number of main meals and the hour of the last meal was compared between current, former, and never night shift workers. Adjusted ORs or predicted means were calculated, as a measure of the associations between night shift work and lifestyle factors, with age, marital status and education included in the models as covariates. Recreational inactivity (defined here as less than one hour per week of recreational physical activity) was associated with current night shift work when compared to never night shift workers (OR = 2.43, 95% CI: 1.13-5.22) among men. Alcohol abstinence and later time of the last meal was associated with night shift work among women. Statistically significant positive relationship between night shift work duration and BMI was observed among men (p = 0.029). This study confirms previous studies reporting lower exercising among night shift workers and tendency to increase body weight. This finding provides important public health implication for the prevention of chronic diseases among night shift workers. Initiatives promoting physical activity addressed in particular to the night shift workers are recommended.

0062 Rotating night shift work in nurses and midwives and lifestyle

ObjectivesTo investigate the association between rotating night shift work and selected modifiable lifestyle factors among nurses and midwives.MethodThe cross-sectional study included 725 nurses and midwives aged 40–60 (354 rotating night...

Association between shift work and obesity among female nurses: Korean Nurses’ Survey

BackgroundShift work has been hypothesized as a risk factor for obesity. In this study, we investigated the association between current shift work and body mass index (BMI) among female nurses in Korea. The relationship between duration of shift work and BMI of the participants was also evaluated.MethodsThis cross-sectional survey evaluated participants in the Korean Nurses’ Survey, conducted from October to December 2011, using web-based self-administered questionnaires. A total of 9,989 nurses were included among 10,000 who registered on the survey web site (5,287 shift workers and 4,702 non-shift workers). Current shift workers were divided into tertiles of shift work duration (0.08–3.00 years, n = 1,732; 3.08–6.75 years, n = 1,731; and 6.83–38.00 years, n = 1,686). The BMI thresholds of overweight and obesity were ≥23 kg/m2 and ≥25 kg/m2, respectively. Data were analyzed using SPSS software.ResultsMean participant age was 33.2 ± 8.6 years and the mean BMI was 20.9 ± 2.5 kg/m2. There were statistically significant differences in current smoking status, regular drinking habit, dietary habits, regular exercise, sleep problems and self-perceived health status according to duration of shift work. The overall prevalence of overweight/obesity (18.6%) and obesity (7.4%) increased significantly as shift work duration increased from the lowest to highest tertile (P for trend <0.001). Multivariate logistic regression analysis revealed no association between current shift work and BMI. However, after adjusting for potential confounders, the participants with the longest duration of shift work were 1.63 (95% CI, 1.22–2.17) times more likely to be overweight or obese than those with the shortest duration. There was a significant positive association between obesity and shift work duration in the unadjusted analysis; however, it was attenuated and no longer significant in the multivariate model.ConclusionsThe duration of shift work was positively associated with prevalence of overweight/obesity in nurses in Korea. Although these findings need to be confirmed in prospective studies, they suggest that special attention should be paid to female nurses with a long duration of shift work.

Shift Work and Cognition in the Nurses' Health Study

Rotating night-shift work, which can disrupt circadian rhythm, may adversely affect long-term health. Experimental studies indicate that circadian rhythm disruption might specifically accelerate brain aging; thus, we prospectively examined shift-work history at midlife as associated with cognitive function among older women in the Nurses' Health Study. Women reported their history of rotating night-shift work in 1988 and participated in telephone-based cognitive interviews between 1995 and 2001; interviews included 6 cognitive tests that were subsequently repeated 3 times, at 2-year intervals. We focused on shift work through midlife (here, ages 58-68 years) because cognitive decline is thought to begin during this period. Using multivariable-adjusted linear regression, we evaluated mean differences in both "average cognitive status" at older age (averaging cognitive scores from all 4 interviews) and rates of cognitive decline over time across categories of shift-work duration at midlife (none, 1-9, 10-19, or ≥20 years). There was little association between shift work and average cognition in later life or between shift work and cognitive decline. Overall, this study does not clearly support the hypothesis that shift-work history in midlife has long-term effects on cognition in older adults.

42 Rotating night shift work and health status among nurses and midwives

ObjectiveNight shift work has been linked to several chronic diseases such as gastrointestinal disorders, cardiovascular disease and diabetes, although the epidemiological data for rotating night shift nurses are inconclusive. The...

The effects of shift work on sleeping quality, hypertension and diabetes in retired workers.

BackgroundShift work has been associated with adverse health effects by disturbing circadian rhythms. However,its potential long-term health effects and the persistent effects after leaving shifts have not been well established.Methods and ResultsWe studied 26,463 workers from Tongji-Dongfeng Cohort in China. All the participants are retired employees of Dongfeng Motor Company. Information on demographics, occupational history and medical history were gathered through questionnaires. After adjusting potential confounders in the logistic regression models, shift work was associated with poor sleeping quality, diabetes and hypertension independently. We observed significant effects of shift work on poor sleeping quality, diabetes and hypertension; the ORs (95%CI) are 1.18 (1.09–1.27), 1.10 (1.03–1.17) and 1.05 (1.01–1.09) respectively. In the further analysis, we found elevated ORs (95%CI) for participants with poor sleeping quality, the ORs (95%CI) are 1.34 (1.08–1.60), 1.13 (1.05–1.21), 1.05 (1.03–1.07) and 1.05 (1.01–1.09) for 1–4, 5–9, 10–19, ≥20 years of shift work respectively. However, with the extension of leaving shift work duration, the effects of shift work on sleep quality gradually reduced.ConclusionsShift work may be an independent risk factor for sleeping quality, diabetes and hypertension even in retired workers. Applicable intervention strategies are needed for prevention of sleep loss, diabetes, and hypertension for shift workers.

PRACA W NOCY A PROLAKTYNA JAKO CZYNNIK RYZYKA RAKA PIERSI

Prolactin - a hormone secreted in a circadian rhythm acts as a regulator of growth and development of the mammary glands. It has been observed that working at night increases breast cancer risk in women. Night shift work, probably carcinogenic to humans (Group 2A IARC), can disrupt a circadian rhythm, and thus potentially alter the rhythm of prolactin secretion. The aim of our work was to review epidemiological evidence on the association between prolactin and the risk of breast cancer and the influence of work at night on prolactin secretion. Search was done in the Medline database by keywords (shift work, work at night, risk of breast cancer and prolactin). 'The increased proliferation of breast cells activated by prolactin can promote the development of cancer. The results of the largest epidemiological prospective studies suggest the association between prolactin levels and the risk of breast cancer in women. So far, only seven studies have investigated the association between work at night and prolactin secretion. In three studies lower concentrations of prolactin have been observed in night shift workers. No relationship between the night shift work duration and prolactin level in women have been reported. Night shift work can modify the profile of prolactin secretion in night workers, probably decreasing the secretion of this hormone at night. It is therefore unlikely that prolactin plays an important role in the development of breast cancer in women working at night. This conclusion is based on the results of a few epidemiological studies.

A retrospective cohort study of shift work and risk of cancer-specific mortality in German male chemical workers

Human evidence of carcinogenicity concerning shift work is inconsistent. In a previous study, we observed no elevated risk of total mortality in shift workers followed up until the end of 2006. The present study aimed to investigate cancer-specific mortality, relative to shift work. The cohort consisted of male production workers (14,038 shift work and 17,105 day work), employed at BASF Ludwigshafen for at least 1 year between 1995 and 2005. Vital status was followed from 2000 to 2009. Cause-specific mortality was obtained from death certificates. Exposure to shift work was measured both as a dichotomous and continuous variable. While lifetime job history was not available, job duration in the company was derived from personal data, which was then categorized at the quartiles. Cox proportional hazard model was used to adjust for potential confounders, in which job duration was treated as a time-dependent covariate. Between 2000 and 2009, there were 513 and 549 deaths among rotating shift and day work employees, respectively. Risks of total and cancer-specific mortalities were marginally lower among shift workers when taking age at entry and job level into consideration and were statistically significantly lower when cigarette smoking, alcohol intake, job duration, and chronic disease prevalence at entry to follow-up were included as explanatory factors. With respect to mortality risks in relation to exposure duration, no increased risks were found in any of the exposure groups after full adjustment and there was no apparent trend suggesting an exposure-response relation with duration of shift work. The present analysis extends and confirms our previous finding of no excess risk of mortality associated with work in the shift system employed at BASF Ludwigshafen. More specifically, there is also no indication of an increased risk of mortality due to cancer.

Rotating night shift work and polymorphism of genes important for the regulation of circadian rhythm

People living in industrialized societies have developed specific working schedules during the day and at night, including permanent night shifts and rotating night shifts. The aim of this study was to examine the association between circadian polymorphisms and rotating night shift work. This cross-sectional study comprised 709 nurses and midwives (348 current rotating and 361 current day workers). Genetic polymorphism of selected clock genes BMAL1 (rs2279287), CLOCK (rs1801260), PER1 (rs2735611), PER2 (rs2304672), PER3 (rs10462020), CRY1 (rs8192440), CRY2 (rs10838527, rs10838527) was determined using real-time polymerase chain reaction (PCR) assays. There were no differences in BMAL1, CLOCK, CRY2, PER1, PER2, and PER3 genotypes among nurses and midwives working rotating night and day shifts. The frequency of women with rare CRY1 TT genotype was higher in the group of rotating night shift than day workers (17.0% versus 13.9%, P=0.06). Moreover, CRY1 TT genotype was associated with the total rotating shift-work duration, compared to women rarely working night shifts. These results suggest that CRY1 (rs8192440) polymorphism may influence the adaptation to the rotating night shift work among nurses and midwives.

Work at night and breast cancer – report on evidence-based options for preventive actions

In 2007, the International Agency for Research on Cancer classified shift work involving circadian disruption as probably carcinogenic to humans (group 2A), primarily based on experimental and epidemiologic evidence for breast cancer. In order to examine options for evidence-based preventive actions, 16 researchers in basic, epidemiological and applied sciences convened at a workshop in Copenhagen 26-27 October 2011. This paper summarizes the evidence from epidemiological and experimental studies and presents possible recommendations for prevention of the effects of night work on breast cancer. Among those studies that quantified duration of shift work, there were statistically significant elevations in risk only after about 20 years working night shift. It is unclear from these studies whether or not there is a modest but real elevated risk for shorter durations. Hence, restriction of the total number of years working night shift could be one future preventive recommendation for shift workers. The diurnal secretion of melatonin by the pineal gland with peak in secretory activity during the night is a good biochemical marker of the circadian rhythm. Disruption of the diurnal melatonin secretion pattern can be diminished by restricting the number of consecutive night shifts. Reddish light and reduced light intensity during work at night could potentially help diminish the inhibitory activity of light with strong intensity on the melatonin secretion, but further mechanistic insight is needed before definite recommendations can be made. Earlier or more intensive mammography screening among female night shift worker is not recommended because the harm-benefit ratio in this age group may not be beneficial. Preventive effects of melatonin supplementation on breast cancer risk have not been clearly documented, but may be a promising avenue if a lack of side effects can be shown even after long-term ingestion. Women with previous or current breast cancer should be advised not to work night shifts because of strong experimental evidence demonstrating accelerated tumor growth by suppression of melatonin secretion. Work during the night is widespread worldwide. To provide additional evidence-based recommendations on prevention of diseases related to night shift work, large studies on the impact of various shift schedules and type of light on circadian rhythms need to be conducted in real work environments.

Rotating Night Shift Work and Risk of Type 2 Diabetes: Two Prospective Cohort Studies in Women

Rotating night shift work disrupts circadian rhythms and has been associated with obesity, metabolic syndrome, and glucose dysregulation. However, its association with type 2 diabetes remains unclear. Therefore, we aimed to evaluate this association in two cohorts of US women. We followed 69,269 women aged 42-67 in Nurses' Health Study I (NHS I, 1988-2008), and 107,915 women aged 25-42 in NHS II (1989-2007) without diabetes, cardiovascular disease, and cancer at baseline. Participants were asked how long they had worked rotating night shifts (defined as at least three nights/month in addition to days and evenings in that month) at baseline. This information was updated every 2-4 years in NHS II. Self-reported type 2 diabetes was confirmed by a validated supplementary questionnaire. We documented 6,165 (NHS I) and 3,961 (NHS II) incident type 2 diabetes cases during the 18-20 years of follow-up. In the Cox proportional models adjusted for diabetes risk factors, duration of shift work was monotonically associated with an increased risk of type 2 diabetes in both cohorts. Compared with women who reported no shift work, the pooled hazard ratios (95% confidence intervals) for participants with 1-2, 3-9, 10-19, and ≥20 years of shift work were 1.05 (1.00-1.11), 1.20 (1.14-1.26), 1.40 (1.30-1.51), and 1.58 (1.43-1.74, p-value for trend <0.001), respectively. Further adjustment for updated body mass index attenuated the association, and the pooled hazard ratios were 1.03 (0.98-1.08), 1.06 (1.01-1.11), 1.10 (1.02-1.18), and 1.24 (1.13-1.37, p-value for trend <0.001). Our results suggest that an extended period of rotating night shift work is associated with a modestly increased risk of type 2 diabetes in women, which appears to be partly mediated through body weight. Proper screening and intervention strategies in rotating night shift workers are needed for prevention of diabetes.

교대근무간호사의 건강증진생활양식수준과 영향요인

Purpose: This descriptive study was to examine the effect factors on health promotion lifestyle of shift work nurses. Methods: The 418 working nurses who completed questionnaires with consent were analysed. Results: The average level of health promotion lifestyle of shift work nurses was 2.21 and it was significantly lower than 2.36 of fixed work nurses. In shift work nurses, the highest health promotion lifestyle was personal relationship of 2.79 and the lowest was physical activity of 1.58. The young, shorter shift work duration, unmarried and general nurses were evaluated as not-healthy diet. The old, longer shift work duration and married showed less physical activity. Less self-efficacy and more job stress, depression, fatigue showed lower health promotion lifestyle. Conclusion: Self-efficacy on health behavior of shift work nurses was the most effective factor on all areas of health promotion. Therefore, we need to develop a health promotion program including self-efficacy encouragement. We suggest that this program be more effective when more precisely characterized according to age, marital status, shift work duration, job position, and psychological problems such as depression and fatigue.

The influence of shift work and light at night exposure on melatonin levels and breast cancer risk

ObjectivesWork at night has been identified as a risk factor for several cancer sites, and melatonin, a hormone that follows a circadian rhythm, has been proposed as an intermediate in...

Shiftwork Duration and the Awakening Cortisol Response Among Police Officers

Police officers are required to work irregular hours, which induces stress, fatigue, and sleep disruption, and they have higher rates of chronic disease and mortality. Cortisol is a well-known “stress hormone” produced via activation of the hypothalamic-pituitary-adrenal axis. An abnormal secretion pattern has been associated with immune system dysregulation and may serve as an early indicator of disease risk. This study examined the effects of long- and short-term shiftwork on the cortisol awakening response among officers (n = 68) in the Buffalo Cardio-Metabolic Occupational Police Stress (BCOPS) pilot study (2001–2003). The time each officer spent on day (start time: 04:00–11:59 h), afternoon (12:00–19:59 h), or night (20:00–03:59 h) shifts was summarized from 1994 to examination date to characterize long-term (mean: 14 ± 9 yrs) and short-term (3, 5, 7, or 14 days prior to participation) shiftwork exposures. The cortisol awakening response was characterized by summarizing the area under the curve (AUC) for samples collected on first awakening, and at 15-, 30-, and 45-min intervals after waking. Data were collected on a scheduled training or off day. The cortisol AUC with respect to ground (AUCG) summarized total cortisol output after waking, and the cortisol AUC with respect to increase (AUCI) characterized the waking cortisol response. Officers also completed the Center for Epidemiologic Studies Depression scale. Waking cortisol AUC values were lower among officers working short-term night or afternoon shifts than day shifts, with maximal differences occurring after 5 days of shiftwork. The duration of long-term shiftwork was not associated with the cortisol awakening response, although values were attenuated among officers with more career shift changes. (Author correspondence: burch@mailbox.sc.edu)

Association of onset of obesity with sleep duration and shift work among Japanese adults

Objective The objective of this longitudinal epidemiological study was to investigate the association of risk factors for cardiovascular illness with sleep duration and shift work. Methods This study used data obtained at medical checkups conducted in 1999 and 2006 for the employees of a local government organization in Japan (covering 21,693 male employees and 2109 female employees). The medical checkup data included (1) body measurements, (2) blood test parameters, and (3) replies to a self-administered questionnaire (inquiring about sleep duration, with or without shift work, etc.). On the basis of these data, we conducted multiple logistic regression analyses to study the association between the risk of new-onset obesity, hypertension, hyperglycemia, hypertriglyceridemia, and hypo-high density lipoprotein (HDL) cholesterolemia and shift work as well as sleep duration. Results Among the male subjects who were engaged in shift work, the relative risk of new-onset obesity for those with a sleep duration of less than 5 h was 1.30 (95% CI, 1.14–1.49) higher than for those with sleep duration of 5–7 h. Furthermore, analysis using both engagement in shift work and sleep duration as dependent variables showed that the relative risks of new-onset obesity for those with a sleep duration of less than 5 h were 1.20 (95% CI, 1.09–1.32) for men and 1.7 (95% CI, 1.11–2.87) for women. Conclusions Short sleep duration is associated with onset of obesity.

ESTIMATION OF THE BENCHMARK DURATION OF SHIFTWORK ASSOCIATED WITH WEIGHT GAIN IN MALE JAPANESE WORKERS

The authors estimated the benchmark durations (BMDs) and their 95% lower confidence limit (BMDL) for the reference duration of shiftwork for weight gain. A 14-yr prospective cohort study was conducted in male workers at a Japanese steel company (n = 7254) who had received annual health check-ups between 1991 and 2005. The endpoints in the study were either a 5%, 7.5%, or 10% increase in body mass index (BMI) during the period of observation, compared to the BMI at entry. The association between the duration of shiftwork and weight gain was investigated using multivariate pooled logistic regression analyses with stepwise selection of covariates, including age, BMI measured during the study, drinking and smoking habits, and habitual exercise. The BMDL/BMD for shiftwork in subjects aged in their 40s or ≥50 yrs was estimated using benchmark responses (BMRs) of 5% or 10% and parameters for the duration of shiftwork and other covariates. For workers aged in their 40s, the BMDL/BMD for shiftwork with a BMR of 5% was 18.6/23.0 yrs (≥7.5%) and 16.9/19.4 yrs (≥10%). For workers aged ≥50 yrs, the BMDL/BMD with a BMR of 5% was 22.9/28.2 yrs (≥7.5%) and 20.6/23.6 yrs (≥10%). The reference duration of shiftwork that associated with weight gain was shown to be at least 17 yrs in middle-aged workers. Special attention should be paid to prevent weight gain at an earlier stage and not when this increase in weight has become apparent. (Author correspondence: suwa@faculty.chiba-u.jp)