Day and night work: changes in cholesterol, uric acid, glucose and potassium in serum and in circadian patterns of urinary catecholamine excretion. A longitudinal cross-over study of railway workers

Cardiovascular risk factors among nurses: A global systematic review and meta-analysis

BACKGROUND

Nurses as the largest group of health workers have a very stressful job which can cause number of diseases specially increase cardiovascular risk factors. This study aims to investigate the overall epidemiology of cardiovascular disease (CVD) risk factors among nurses.

METHOD

We searched all four main databases such as Scopus, PubMed, Embase and Web of Sciences from the beginning of 2000 to March 2022 with appropriate Mesh Terms. We also searched Google scholar. Then we applied inclusion and exclusion criteria and after selection the studies the Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of included studies. Comprehensive Meta-analysis and R software was used for analysis.

RESULTS

Finally, 22 articles with a total number of 117922 nurses were included. Among all risk factors, sedentary lifestyle and lack of regular physical activity with a prevalence of 46.3% (CI 95%, 26.6-67.2) was regarded as the main prevalent risk factor among nurses. The mean systolic blood pressure (SBP) measured in the study population was 121.31 (CI 95%, 114.73-127.90) and the mean diastolic blood pressure (DBP) was 78.08 (CI 95%, 74.90-81.25). Also family history of cardiovascular disease (41.9%; 95% IC: 29.8-55.1%), being overweight (33.3%; 95% IC: 24.7-43.2%), and alcohol consumption (24.6%; 95% IC: 16.4-35.2%) was found among the participants.

CONCLUSION

Study results revealed that sedentary lifestyle was the main prevalent CVD risk factor among nurses followed by family history of cardiovascular disease, being overweight and alcohol consumption. Furthermore, among nurses with shift works almost all risk factors got higher score representing the worse condition in comparison with day workers' nurses. This study enables learning the associated risk factors of CVD among nurses to facilitate interventional programs with a view to reduce the exposure of nursing staff particularly those who work in shifts to cardiovascular risk factors.

1. WHAT WAS ALREADY KNOWN?

In general, many studies have emphasized the impact of the nursing profession on the incidence of some cardiovascular patients. Also, different shifts of nurses can have a double effect.

2. WHAT ARE THE NEW FINDINGS?

In this study, the mean for sedentary lifestyle was reported to be 46.3% which represented the most prevalent risk factor for cardiovascular risk factors among study population.

3. WHAT IS THEIR SIGNIFICANCE?

This study enables learning the associated risk factors of CVD among nurses to facilitate interventional programs with a view to reduce the exposure of nursing staff particularly those who work in shifts to cardiovascular risk factors. This information can comprise essential tools for health human resource management contributing to advance nursing.

Effectiveness of sleep interventions for rotating night shift workers: a systematic review and meta-analysis

Background

Sleep disturbance is a common issue among rotating night shift workers and is closely related to health risks. The present study aimed to determine the effectiveness of pharmacological and non-pharmacological sleep interventions for the management of sleep disturbance among rotating night shift workers.

Methods

For this systematic review and meta-analysis, we searched six electronic databases-EMBASE, CINAHL, Cochrane Library, PubMed, Scopus, and Web of Science-for randomized controlled trials and clinical trials published from January 1990 to June 2022. The quality of eligible studies was independently assessed by three authors using the Joanna Briggs Institute Critical Appraisal Checklist for randomized controlled trials and quasi-experimental studies. The meta-analysis was performed based on the random effects model using the Comprehensive Meta-Analysis software. The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Results

Of the 1019 studies retrieved, 30 met the inclusion criteria for the systematic review; 25 were selected for the meta-analysis. Sleep interventions were categorized as follows: pharmacological approach (n = 7), light therapy (n = 9), cognitive behavioral approach (n = 7), aroma or alternative therapy (n = 4), and shift schedule modification (n = 3). The overall mean effect size of the interventions was moderate (Hedges' g = 0.59; 95% confidence interval = 0.33-0.84, z = 4.50, p < 0.001).

Conclusion

Sleep interventions were effective in promoting sleep or reducing sleep disturbance among rotating night shift workers. These findings provide evidence of the effectiveness of various pharmacological and non-pharmacological sleep interventions for managing sleep health in the work environment of rotating night shift workers.

The relationships of shift work, hair cortisol concentration and dyslipidaemia: a cohort study in China

BACKGROUND

Currently, cardiovascular disease is the leading cause of death, and dyslipidaemia is an independent and modifiable major risk factor. Previous studies on shift work with dyslipidaemia and hair cortisol concentration (HCC) have yielded conflicting results. The aim of this study was to clarify the association between shift work, dyslipidaemia, and HCC. We further explored the mediating effect of HCC.

METHODS

In this cohort study, baseline data were collected from participants in May 2013. The cohort included 2170 participants- 1348 shift workers and 822 non-shift workers- who were followed up for 6 years with four questionnaire surveys from July 2014, October 2015, and May to December 2019. Hair samples were collected from 340 participants during the baseline period for HCC testing with an automated radioimmunoassay. Dyslipidaemia was defined using the National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria.

RESULTS

Shift workers had a higher risk of dyslipidaemia than workers on the fixed day shift (two-shift RR = 1.408, 95% CI: 1.102-1.798; three-shift RR = 1.478, 95% CI: 1.134-1.926; four-shift RR = 1.589, 95% CI: 1.253-2.015). Additionally, shift workers had higher HCC levels than fixed day shift workers, with geometric mean concentration (GMC) ± geometric standard difference (GSD) = 2.625 ± 2.012 ng/g, two-shift GMC ± GSD = 3.487 ± 1.930 ng/g, three-shift GMC ± GSD = 2.994 ± 1.813 ng/g, and four-shift GMC ± GSD = 3.143 ± 1.720 ng/g. High HCC was associated with a high incidence of dyslipidaemia. After controlling for confounding factors, this study showed that HCC played a role in mediating dyslipidaemia in shift workers and accounted for 16.24% of the effect.

CONCLUSIONS

Shift work was linked to increased risk of dyslipidaemia compared with fixed day shift work. Higher HCC was associated with a higher prevalence of dyslipidaemia. HCC had a significant mediating effect on dyslipidaemia in shift workers.

Carotid intimal medial thickness in rotating night shift is related to IL1β/IL6 axis

BACKGROUND AND AIMS

Sleep disturbances may promote glucose abnormalities and inflammatory burden among shift workers. Therefore, precocious subclinical atherosclerotic process might develop in healthy shift workers even without known metabolic and cardiovascular risk factors.

METHODS AND RESULTS

We measured anthropometric parameters, glucose, lipids, inflammation and common carotid Intimal Medial Thickness (cIMT) in rotating-night shift workers (r-NSW, n = 88, age = 40.3 ± 7.8 y) in comparison with former-night shift workers (f-NSW, n = 35, age = 44.2 ± 6.4 y) and with day-only workers (DW, n = 64, age = 44.1 ± 8.9 y). R-NSW and f-NSW showed significantly higher cIMT and high sensitivity C-Reactive Protein (hs-CRP) respect to DW (p = 0.043 and p = 0.025, respectively). IL-1β levels were higher in r-NSW than in DW and f-NSW (p = 0.043) and significantly correlated with IL6 (r = 0.365, p < 0.001). In addition, r-NSW and f-NSW had higher HbA1c levels in comparison with DW (p = 0.047). Carotid-IMT was significantly related to night shift work (p = 0.023), with age (p < 0.001), with HOMA IR (p = 0.009), with insulin (p = 0.006) with HbA1c (p = 0.002), with LDL cholesterol (p < 0.001), with diastolic BP (p < 0.001), with WBC (p = 0.002) and with IL6 (p = 0.004). After performing a multivariate analysis night shift work remained statistically related to cIMT (B = 2.633, 95%CI = 0.489-4.776, p = 0.016).

CONCLUSIONS

Our result described a possible link bridging night shift work, inflammation and carotid Intimal Medial Thickness. Future studies are warranted to understand if carotid atherosclerosis process should be mainly driven by the IL1β/IL6 citokine axis connected to sleep disturbances.

Shift work, and particularly permanent night shifts, promote dyslipidaemia: A systematic review and meta-analysis

BACKGROUND AND AIMS

Shift work is common worldwide and linked to deleterious cardiovascular effects that might be underlined by dyslipidemia. The aim of this systematic review and meta-analysis is to determine the impact of shiftwork on dyslipidemia.

METHODS

Searching in PubMed, Cochrane Library, Science Direct and Embase databases without language restriction on 15 February 2020, included studies that describe blood lipids levels or a risk measure in shift workers compared with fixed-day workers (controls). Differences by study-level characteristics were estimated using stratified meta-analysis by type of shift work, and meta-regression to examine relations between dyslipidemia and demographic, lifestyle and work characteristics. Estimates were pooled using random-effect meta-analysis.

RESULTS

We included a total of 66 articles, representing 197,063 workers. Shift work globally increased the levels of triglycerides (overall SMD = 0.09; 95CI 0.05 to 0.13; p < 0.001), and globally decreased the levels of c-HDL (-0.08; 95CI -0.12 to -0.03; p = 0.001). Permanent night shift workers were an at-risk type of shift for dyslipidemia with significantly higher blood levels of total cholesterol (0.22; 95CI 0.01 to 0.42; p = 0.043) and triglycerides (0.18; 0.03 to 0.33; p = 0.017), and significantly lower blood levels of c-HDL (-0.16; 95CI -0.32 to 0.00; p = 0.05). Permanent night shift workers were more at-risk for total cholesterol than rotating 3 × 8 shift workers (Coefficient 0.22; 95CI 0.01 to 0.42; p = 0.038) and rotating 2 × 12 shift workers (0.24; 0.02 to 0.46; p = 0.037), and more at-risk for triglycerides than rotating day shift workers (0.21; 95CI 0.03 to 0.38; p = 0.023). Results were non-significant for c-LDL, nor depending on type of shifts.

CONCLUSIONS

Shift work, and particularly permanent night shift, is associated with dyslipidaemia via elevated total cholesterol and triglycerides, and reduced HDL-cholesterol. Our current study provides a practical and valuable strengthening of the evidence-base required for preventive health initiatives and workplace reform.

High-Intensity Training Reduces CVD Risk Factors among Rotating Shift Workers: An Eight-Week Intervention in Industry

Rotating shift work is associated with risk factors for cardiovascular disease (CVD). We have studied the effect of 17 min high-intensity training three times a week over eight weeks on CVD risk factors among shift workers. Sixty-five shift workers from two plants were recruited. They were all deemed healthy at the initial health screening and in 100% work. From plant A, 42 workers, and plant B, 23 workers participated. After the intervention, 56 workers were retested. The intervention group consisted of 19 participants from plant A who had participated in at least 10 sessions. Twenty workers from plant B and 17 workers from plant A that not had taken part in the training were included in the control group. All workers reported physical activity (PA) by questionnaires before and after the training intervention. We measured blood pressure, heart rate, lipids, glycated hemoglobin (HbA1c), and C-reactive protein (CRP) and arterial stiffness. Maximal oxygen uptake (V.O_2max) was assessed by bicycle ergometry. The intervention group favorably differed significantly from the control group in improvement of systolic and diastolic blood pressure and glycated hemoglobin (HbA1c). Short training sessions with 4 min of high-intensity PA, three times a week, for eight weeks among rotating shift workers reduced some CVD risk factors. PA interventions in occupational settings may thus decrease coronary heart disease and stroke incidences in this vulnerable group of workers.

Comparison of nighttime and daytime operation on outcomes of kidney transplant with deceased donors: a retrospective analysis

Background:

Kidney transplant is always emergent operations and frequently need to be performed at nighttime to reduce cold ischemia time (CIT). Previous studies have revealed that fatigue and sleep deprivation can result in adverse consequences of medical procedures. This study aimed to evaluate whether nighttime operation has adverse impact on kidney transplant.

Methods:

A retrospective analysis of recipients accepted kidney transplant from deceased donors in one center from 2014 to 2016 was performed. Daytime transplant was defined as operation started after 8 am or ended before 8 pm and nighttime operation was defined as operation ended after 8 pm or started before 8 am. The incidences of complications such as delayed graft function, acute rejection, surgical complications and nosocomial infections were compared between 2 groups. Student's t-test was used to analyze continuous variables such as serum creatinine (Scr) at 1-year of post-transplant. The Chi-square test was used to analyze categorical variables. Differences in recipients and graft survival were analyzed using Kaplan–Meier methodology and log-rank tests.

Results:

Among the 443 recipients, 233 (52.6%) were classified into the daytime group and the others 210 (47.4%) were in the nighttime group. The 1-year survival rate of recipients was similar for the recipients in the daytime and nighttime groups (95.3% vs. 95.2%, P = 0.981). Although the 1-year graft survival rate in the nighttime group was slightly superior to that in the daytime group, the difference was not significant (92.4% vs. 88.4%, P = 0.164). Furthermore, Scr and incidence of complications were also not significantly different between the 2 groups.

Conclusions:

Our results suggested that operation time of kidney transplant with short CIT has no significant impact on the outcome of kidney transplant. Nighttime operation of kidney transplant with short CIT could be postponed to the following day to alleviate the burden on medical staffs and avoid the potential risk.

Shift Work Including Night Work and Long Working Hours in Industrial Plants Increases the Risk of Atherosclerosis

There is an abundance of literature reporting an association between shift work and cardiovascular disease (CVD). Few studies have examined early manifestation of CVD using advanced modern methodology. We established a group of 65 shift workers and 29 day workers (controls) in two industrial plants. For the shift workers, the shift schedule includes rotating shifts with day, evening and nightshifts, some day and nightshifts lasting for 12 h. The current paper describes cross-sectional data in a study running for three years. We collected background data by questionnaire and measured blood pressure, heart rate, lipids, glycosylated hemoglobin (HbA1c) and C-reactive protein (CRP). We examined arterial stiffness (central blood pressure, augmentation pressure and index, and pulse wave velocity) by the use of SphygmoCor^® (AtCor Medical Pty Ltd, Sydney, Australia) and the carotid arteries by ultrasound. We assessed VO_2max by bicycle ergometry. We applied linear and logistic regression to evaluate associations between total number of years in shift work and cardiovascular outcome measures. The day workers were older and had more pronounced arterial stiffness compared to the shift workers. Number of years as a shift worker was associated with increased carotid intima media thickness (max IMT) (B = 0.015, p = 0.009) and an elevated CRP (B = 0.06, p = 0.03). Within the normal range for this age group, VO_2max was 41 (9) ml/kg/min. Rotating shift work including day and night shifts lasting up to 12 h and evening shifts are associated with CVD-risk factors. This could imply an increased risk for coronary heart disease and stroke among these workers. Therefore, preventive measures should be considered for these groups of workers in order to prevent such diseases.

Chronic health disparities among refugee and immigrant children in Canada

There are knowledge gaps in our understanding of the development of chronic disease risks in children, especially with regard to the risk differentials experienced by immigrants and refugees. The Healthy Immigrant Children study employed a mixed-methods cross-sectional study design to characterize the health and nutritional status of 300 immigrant and refugee children aged 3-13 years who had been in Canada for less than 5 years. Quantitative data regarding socioeconomic status, food security, physical activity, diet, and bone and body composition and anthropometric measurements were collected. Qualitative data regarding their experiences with accessing health care and their family lifestyle habits were gathered through in-depth interviews with the parents of newcomer children. Many newcomers spoke about their struggles to attain their desired standard of living. Regarding health outcomes, significantly more refugees (23%) had stunted growth when compared with immigrants (5%). Older children, those with better-educated parents, and those who consumed a poorer-quality diet were at a higher risk of being overweight or obese. Sixty percent of refugees and 42% of immigrants had high blood cholesterol. Significant health concerns for refugee children include stunting and high blood cholesterol levels, and emerging trends indicate that older immigrant children from privileged backgrounds in low-income countries may be more at risk of overweight and obesity. A variety of pathways related to their families' conceptualization of life in Canada and the social structures that limit progress to meeting their goals likely influence the development of health inequity among refugee and immigrant children. Public health initiatives should address these health inequities among newcomer families.

Prevention of fatigue and insomnia in shift workers-a review of non-pharmacological measures

Background

Excessive fatigue and insomnia are common among shift workers and can lead to negative effects such as reduced work performance, processing errors, accidents at work, absenteeism, reduced quality of life, and symptoms of depression. Moreover, work in rotating shifts can be a risk factor for different somatic and psychiatric diseases and may contribute to poor health, especially in elder adults and women. This review aims to show non-pharmacological preventive measures against fatigue and insomnia in shift workers.

Method

Computerized literature searches in MedLine and in the Cochrane Library were performed with the following key words: shift work disorder, fatigue, insomnia, shift work, measures, treatment, therapy, strategies and coping. The search was limited to non-pharmacological studies that were conducted on human subjects and published as English-language articles in peer-reviewed journals since 1970. Additional studies were identified through the reference sections of relevant articles. Eighteen articles on fatigue in shift workers, including six original research articles with a total sample size of 3504 probands consisting of industrial workers, office employees, aircraft maintenance engineers, and non-shift workers working in simulated shifts, were analyzed, as well as seven articles on insomnia, including an original research article with a sample size of 26 media workers. Also, 4 reviews on shift work disorder were analyzed.

Main

The occurrence of fatigue and insomnia in shift workers associated with a working period is described as shift work disorder. Estimations on the prevalence of shift work disorder in shift workers vary between 5 % and about 20 %; about one in three shift workers is affected by insomnia and up to 90 % of shift workers report regular fatigue and sleepiness at the workplace. We concluded that there is a necessity for treatments to improve the sleep quality of the shift working population. The most common non-pharmacological recommendations to improve sleep quality and to reduce insomnia and fatigue were scheduling, bright light exposure, napping, psychoeducation for sleep hygiene, and cognitive-behavioral measures.

Conclusion

Some important preventive coping strategies for fatigue associated with shift work such as napping and exposure to bright light have already been investigated and are generally approved. A few studies also provide good evidence for the efficacy of cognitive-behavioral techniques in the treatment of chronic primary and comorbid insomnia. These coping strategies summarized in this paper should be considered in the workplace health promotion programs of each work environment to improve working conditions for shift workers and to save money.

Bedtime Variability and Metabolic Health in Midlife Women: The SWAN Sleep Study

STUDY OBJECTIVES

Circadian misalignment, as seen in shift workers, can disrupt metabolic processes. Associations between sleep timing in nonshift workers and metabolic health are unknown. We examined sleep timing and indices of metabolic health in a community sample of midlife women.

METHODS

Caucasian (n = 161), African American (n = 121) and Chinese (n = 56) non-shift-working women aged 48-58 y who were not taking insulin-related medications, participated in the Study of Women's Health Across the Nation (SWAN) Sleep Study and were subsequently examined approximately 5.39 (standard deviation = 0.71) y later. Daily diary-reported bedtimes were used to calculate four measures of sleep timing: mean bedtime, bedtime variability, bedtime delay and bedtime advance. Body mass index (BMI) and insulin resistance (homeostatic model assessment-insulin resistance, HOMA-IR) were measured at two time points. Linear regressions evaluated whether sleep timing was associated with BMI and HOMA-IR cross-sectionally and prospectively.

RESULTS

In cross-sectional models, greater variability in bedtime and greater bedtime delay were associated with higher HOMA-IR (β = 0.128; P = 0.007, and β = 0.110; P = 0.013, respectively) and greater bedtime advance was associated with higher BMI (β = 0.095; P = 0.047). Prospectively, greater bedtime delay predicted increased HOMA-IR at Time 2 (β = 0.152; P = 0.003). Results were partially explained by shifted sleep timing on weekends.

CONCLUSION

Frequent shifts in sleep timing may be related to metabolic health among non-shift working midlife women.

COMMENTARY

A commentary on this article appears in this issue on page 269.

Evaluation of the effect of shift work on serum cholesterol and triglyceride levels

Background:

Working outside daylight hours (7 am to 7 pm) is called shift work. Shift work is a common practice in many industries and factories such as steel industries, petroleum industries, power plants, and in some services such as medicine and nursing and police forces, in which professionals provide services during day and night.

Objectives:

Considering the contradictory reports of different studies, we decided to evaluate the effect of shift work on cholesterol and triglyceride (TG) levels through a historical cohort on steel industry workers.

Patients and Methods:

This retrospective cohort study was performed on all the staff of Isfahan’s Mobarakeh Steel Company between years 2002 and 2011. There were 5773 participants in this study. Data were collected from the medical records of the staff using the census method. For analysis of data, generalized estimating equation (GEE) regression was used.

Results:

The results showed a significant difference in cholesterol levels between shift workers and day workers on the first observation (P < 0.001), yet no such difference was observed for TG (P = 0.853). Moreover, the results showed that the variables of age, work experience and BMI were not similar between shift workers and day workers. Therefore, to remove the effect of such variables, we used GEE regression. Despite the borderline difference of cholesterol between regular shift workers and day workers, this correlation was not statistically significant (P = 0.051). The results for TG also showed no correlation with shift work.

Conclusions:

According to the findings of this study, there is no relationship between shift work and changes in serum TG and cholesterol. The lack of relationship can be due to shift plans for shift workers, nutrition, or the “Healthy Heart project” at Isfahan Mobarakeh Steel Company.

The association between shift work and hyperuricemia in steelmaking male workers

Objectives

The aim of this study was to examine the association between shift work and hyperuricemia among steel company workers.

Methods

We examined 1,029 male workers at a Korean steel company between June 6 and June 28, 2013. We conducted anthropometric measurements, questionnaire surveys, and blood tests. Hyperuricemia was defined as a serum uric acid concentration of ≥7.0 mg/dL. Logistic regression analyses were performed. In the full model, analysis was adjusted for covariates including age, body mass index, lifestyle factors, and comorbidities. The odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for all models.

Results

The participants included 276 daytime workers and 753 shift workers. Among daytime workers, 72 (26.1%) individuals had hyperuricemia, as did 282 (37.5%) individuals among shift workers (p <0.001). There was a statistically significant association between shift work and hyperuricemia. In the unadjusted model, the OR of shift work was 1.70 (95% CI 1.25-2.31) for hyperuricemia. In the full model, the OR of shift work was also statistically significant after adjustment for covariates (OR 1.41, 95% CI 1.02-1.96).

Conclusions

Among male steel workers, a significant association between shift work and hyperuricemia was observed.

Meta-analysis on night shift work and risk of metabolic syndrome

This study aims to quantitatively summarize the association between night shift work and the risk of metabolic syndrome (MetS), with special reference to the dose-response relationship with years of night shift work. We systematically searched all observational studies published in English on PubMed and Embase from 1971 to 2013. We extracted effect measures (relative risk, RR; or odd ratio, OR) with 95% confidence interval (CI) from individual studies to generate pooled results using meta-analysis approach. Pooled RR was calculated using random- or fixed-effect model. Downs and Black scale was applied to assess the methodological quality of included studies. A total of 13 studies were included. The pooled RR for the association between 'ever exposed to night shift work' and MetS risk was 1.57 (95% CI = 1.24-1.98, pheterogeneity  = 0.001), while a higher risk was indicated in workers with longer exposure to night shifts (RR = 1.77, 95% CI = 1.32-2.36, pheterogeneity  = 0.936). Further stratification analysis demonstrated a higher pooled effect of 1.84 (95% CI = 1.45-2.34) for studies using the NCEP-ATPIII criteria, among female workers (RR = 1.61, 95% CI = 1.10-2.34) and the countries other than Asia (RR = 1.65, 95% CI = 1.39-1.95). Sensitivity analysis confirmed the robustness of the results. No evidence of publication bias was detected. The present meta-analysis suggested that night shift work is significantly associated with the risk of MetS, and a positive dose-response relationship with duration of exposure was indicated.

Main effects of sleep disorders related to shift work-opportunities for preventive programs

The sleep-related problems of shift workers usually occur as transient phenomena related to the timing of work. Sleep disorders, related to sleep deprivation, have a major impact on the quality of life and health status of healthcare workers. Reduced quantity and quality of sleep negatively affects the activities of shift workers, particularly in terms of their social functioning, quality of life and health. However, it seems that health authorities and the medical staff are negligent when it comes to the negative effects on health caused by work in night shifts. Recently published studies in this field suggest that appropriate public health preventive programs dealing with sleep disorders successfully contribute towards the quality of life of workers.

Deficient of a clock gene, brain and muscle Arnt-like protein-1 (BMAL1), induces dyslipidemia and ectopic fat formation

A link between circadian rhythm and metabolism has long been discussed. Circadian rhythm is controlled by positive and negative transcriptional and translational feedback loops composed of several clock genes. Among clock genes, the brain and muscle Arnt-like protein-1 (BMAL1) and circadian locomotor output cycles kaput (CLOCK) play important roles in the regulation of the positive rhythmic transcription. In addition to control of circadian rhythm, we have previously shown that BMAL1 regulates adipogenesis. In metabolic syndrome patients, the function of BMAL1 is dysregulated in visceral adipose tissue. In addition, analysis of SNPs has revealed that BMAL1 is associated with susceptibility to hypertension and type II diabetes. Furthermore, the significant roles of BMAL1 in pancreatic β cells proliferation and maturation were recently reported. These results suggest that BMAL1 regulates energy homeostasis. Therefore, in this study, we examined whether loss of BMAL1 function is capable of inducing metabolic syndrome. Deficient of the Bmal1 gene in mice resulted in elevation of the respiratory quotient value, indicating that BMAL1 is involved in the utilization of fat as an energy source. Indeed, lack of Bmal1 reduced the capacity of fat storage in adipose tissue, resulting in an increase in the levels of circulating fatty acids, including triglycerides, free fatty acids, and cholesterol. Elevation of the circulating fatty acids level induced the formation of ectopic fat in the liver and skeletal muscle in Bmal1 -/- mice. Interestingly, ectopic fat formation was not observed in tissue-specific (liver or skeletal muscle) Bmal1 -/- mice even under high fat diet feeding condition. Therefore, we were led to conclude that BMAL1 is a crucial factor in the regulation of energy homeostasis, and disorders of the functions of BMAL1 lead to the development of metabolic syndrome.

Health promotion and work: prevention of shift work disorders in companies

Workplace health promotion is a strategy to improve the health and well-being of people at work. The measures aim at the personal, organisational and work environment. Shift work is one of many reasons provoking increased job stress. According to worldwide epidemiological data, up to 30% of the working population are employed in shifts. Taking into consideration that shift work causes a large number of somatic and psychiatric diseases which bear considerable negative consequences for the health status and the quality of life, it seems to be important to initiate health promotion strategies for shift workers in the companies. The results of recent studies indicate that well-scheduled und targeted health programmes can change the lifestyle of shift working employees and have an impact on the risk factors involved. One problem, though, is a considerable time lag till effects become apparent; therefore, the long-term economic effects of workplace health promotion have not been evaluated sufficiently to date. These definitely positive effects highlight the demand for trainings and workshops for people in shift work. We urgently suggest a speedy implementation of the recommended strategies by companies with shift work systems. In our view, this poses a challenge to the “infant” interdisciplinary field of sleep medicine that should be solved.

Shift work and arteriosclerosis risk in professional bus drivers

PURPOSE

Professional bus drivers are at increased risk for cardiovascular disease, but the underlying causes are unclear. Professional bus drivers often follow shift schedules. Especially, an association between shift work and early manifestations of cardiovascular disease has not been elucidated. Thus we investigated the links between shift work and arteriosclerosis risk in professional bus drivers.

METHODS

Questionnaires were administered to 184 bus drivers on demographic characteristics, lifestyle, and occupational history from 5 transportation companies in Taiwan. Brachial-ankle pulse wave velocity (baPWV) was measured using a volume-plethysmographic apparatus. Body mass index, waist circumference, biochemical variables, and blood pressure were also measured.

RESULTS

Arteriosclerotic risk factors (age, weekly driving hours, systolic blood pressure, diastolic blood pressure, and insulin level) differed in part among different groups of drivers. Long-term shift drivers had higher baPWV compared to regular drivers and short-term shift drivers (1594 cm/s vs. 1497 and 1432, p<0.01). Our multiple regression model showed that age (p<0.01) and diastolic blood pressure (p<0.01) were positively associated with baPWV in our professional drivers. After adjusting for all covariates, we observed that baPWV increased by 3.6 cm/s for per 1-year increment in years of shift driving.

CONCLUSIONS

Long-term shift work could increase the risk of arteriosclerosis in professional bus drivers. Larger studies would be necessary to provide further evidence regarding this finding.

Ventricular arrhythmias and risk indicators of ischemic heart disease

Three groups of men, 50 with manifest ischemic heart disease (IHD), 50 with risk indicators of IHD and 50 healthy men, were examined for ventricular arrhythmias with 24-hour Holter monitoring during normal work and home life. Ventricular arrhythmias were most frequent in the IHD, intermediate in the risk and least frequent in the control group. Multiform ventricular ectopic beats, but no other qualitative characteristic significantly discriminated the three groups. The following risk indicators were associated with ventricular arrhythmias: ageing, cardiac enlargement and smoking. The results suggest that long-term ECG monitoring may be of value for the detection of ventricular arrhythmias not only in men with clinical IHD, but also in those with merely risk indicators.

The influence of sleep and sleep loss upon food intake and metabolism

The present review investigates the role of sleep and its alteration in triggering metabolic disorders. The reduction of the amount of time sleeping has become an endemic condition in modern society and the current literature has found important associations between sleep loss and alterations in nutritional and metabolic aspects. Studies suggest that individuals who sleep less have a higher probability of becoming obese. It can be related to the increase of ghrelin and decrease of leptin levels, generating an increase of appetite and hunger. Sleep loss has been closely associated with problems in glucose metabolism and a higher risk for the development of insulin resistance and diabetes, and this disturbance may reflect decreased efficacy of the negative-feedback regulation of the hypothalamic–pituitary–adrenal axis. The period of sleep is also associated with an increase of blood lipid concentrations, which can be intensified under conditions of reduced sleep time, leading to disorders in fat metabolism. Based on a review of the literature, we conclude that sleep loss represents an important risk factor for weight gain, insulin resistance, type 2 diabetes and dyslipidaemia. Therefore, an adequate sleep pattern is fundamental for the nutritional balance of the body and should be encouraged by professionals in the area.

A prospective cohort study of shift work and risk of ischemic heart disease in Japanese male workers

This study prospectively examined the association between shift work and the risk of ischemic heart disease among Japanese male workers. A baseline survey, which involved 110,792 inhabitants (age range: 40-79 years) from 45 areas throughout Japan, was conducted between 1988 and 1990. The causes of death were identified from death certificates. The analysis was restricted to 17,649 men (age range: 40-59 years) who were employed at the time of the baseline survey. All subjects were asked to indicate the most regular shift work that they had undertaken previously: day work, rotating-shift work, or fixed-night work. The Cox proportional hazards model was used to estimate the risks of shift work for ischemic heart disease. During the 233,869 person-years of follow-up, a total of 1,363 deaths were recorded, 86 of which were due to ischemic heart disease. Compared with the day workers, the rotating-shift workers had a significantly higher risk of death due to ischemic heart disease (relative risk = 2.32, 95% confidence interval: 1.37, 3.95; p = 0.002), whereas fixed-night work was not associated with ischemic heart disease (relative risk = 1.23, 95% confidence interval: 0.49, 3.10; p = 0.658). In addition, subjects with coronary risk factors, such as hypertension, overweight, habitual alcohol consumption, and smoking, were highly susceptible to the effect of rotating-shift work on the risk of death due to ischemic heart disease.

Long-Term Longitudinal Study on the Relationship Between Alternating Shift Work and the Onset of Diabetes Mellitus in Male Japanese Workers

OBJECTIVE

This study investigated the effect of alternating shift work (ASW) on the onset of diabetes mellitus in Japanese workers compared with onset in day-shift work (DSW).

METHODS

A longitudinal study was carried out on a DSW group (n = 3203) and ASW group (n = 2426) of a steel company who received their annual health checkups over a 10-year period between 1991 and 2001. The association between job schedule type and onset of diabetes mellitus (glycated hemoglobin A1c > or =6.0% or medication) was investigated by multivariate pooled logistic regression analyses.

RESULTS

The odds ratio (95% confidence interval) for the development of diabetes mellitus in the ASW group compared with the DSW group was 1.35 (1.05-1.75).

CONCLUSIONS

Our study revealed that the ASW is an independent risk factor for the onset of diabetes mellitus.

A prospective study of night shift work, sleep duration, and risk of Parkinson's disease

The authors prospectively investigated whether working rotating night shifts was associated with the risk of Parkinson's disease among 84,794 female nurses who reported years of night shift work in 1988 (the US Nurses' Health Study). After 975,912 person-years of follow-up (1988-2000), 181 incident Parkinson's disease cases were documented. Compared with nurses who never worked rotating night shifts, those with 15 years or more of night shift work had a 50% lower risk of Parkinson's disease after adjustment for age and smoking (95% confidence interval: 0.26, 0.97; p(trend) = 0.01). Sleep duration was positively associated with Parkinson's disease risk: The relative risk was 1.84 (95% confidence interval: 0.99, 3.42) when comparing nurses who reported 9 or more hours of sleep per day with those who slept 6 hours or less (p(trend) = 0.005). These data suggest that working night shifts may be protective against Parkinson's disease or that low tolerance for night shift work is an early marker of Parkinson's disease. Conversely, habitual longer sleep duration may be an earlier marker of Parkinson's disease. Because of the novelty and the exploratory nature of these findings, confirmation is needed.

Shift working and risk of lipid disorders: a cross-sectional study

BACKGROUND

previous studies have indicated on association between shift work and lipid profile disturbances. Lipid profile disturbances could be due to internal desynchronization. The aim of this study was to analyze whether there is relationship between shift work and serum lipids, fasting blood glucose and hypertension.

RESULTS

A total of 424 rail road workers between the ages of 21 and 64 years in this study filled out a questionnaire, and total cholesterol, triglyceride and HDL-C concentration were measured after 12-hours fasting. Association between shift work and biochemical variables and blood pressure were measured. The X2 and fisher's exact test was used for comparing the qualitative variables and for quantitative variables with normal distribution we used the parametric tests. Odds ratio (OR) with the 95% confidence interval (95% CI) was used for comparing the proportions of risk variables.Sub-populations in this study were consisting of 158 (37.3%) shift workers and 266 (62.7%) day workers. High levels of total cholesterol (> 200 mg/dl) and LDL-cholesterol (> 130 mg/dl) were significantly more prevalent in nearly all groups of shift workers irrespective of age. But there is no differences in the serum levels of triglyceride, HDL-C, fasting blood glucose and blood pressure between shift workers and day workers.Adjusted Odd's ratio for the effect of shift working on high serum total cholesterol and LDL-C level were 2.11(95%CI: 1.33-3.36) and 1.76(95%CI: 1.09-2.83), respectively.

CONCLUSION

This study showed that high serum total cholesterol and LDL-C level were more common in shift workers than in day workers. This finding persisted after adjustment was made for age and food type. But there was no difference in the prevalence of HDL-C, triglyceride, fasting blood glucose and hypertension between shift working and day working. It was concluded that shift work is a risk factor for lipid profile disturbances.

A longitudinal study of the influence of shift work on serum uric acid levels in workers at a telecommunications company

BACKGROUND

Hyperuricemia is a lifestyle-related disease. Although there have been many previous reports about the association of serum uric acid (UA) levels with lifestyle, including eating habits and alcohol intake, there has been no report of a longitudinal study of the relationship between serum UA levels and shift work.

AIMS

To clarify the influence of shift work on serum UA levels in Japanese workers.

METHODS

This was a 4-year cohort study of 15 871 workers at a telecommunications company. Pooled logistic regression analyses by sex were performed, with job schedule type, age, body mass index (BMI), lifestyle and the results of blood chemistries as covariates.

RESULTS

In males, shift work, part-time work, BMI, consumption of alcohol (less than twice per week, two to five times per week or more than five times per week) and little preference for vegetables were positively associated with the development of increased serum UA (>or=8 mg/dl in males, >or=6 mg/dl in females). In females, age, BMI and a history of smoking were positively associated with the development of increased serum UA.

CONCLUSION

This study revealed that shift work is independently related to increased serum UA in males.

Light treatment and circadian adaptation to shift work

Work at unconventional hours can have both long and short term consequences. Shift workers are often required to perform their duties at times that are not favoured by the body's endogenous clock, or circadian pacemaker. A typical night shift worker, for example, may report reductions in alertness and performance during shifts, or significant difficulty attaining sleep of recuperative value in the day, all the while being more likely to develop health complications. The study of circadian physiology has significantly contributed to our current ability to aid the shift worker deal with atypical schedules. We discuss the usefulness of light treatment as a countermeasure for maladaptation to atypical work schedules.

Effect of shift work on body mass index: results of a study performed in 319 glucose-tolerant men working in a Southern Italian industry

OBJECTIVE

To examine the influence of shift work on metabolic and cardiovascular risk factors in subjects working in an industry sited in Apulia, Southern Italy.

DESIGN

Cross-sectional study of metabolic effects of shift work in glucose tolerant workers in a chemical industry in southern Italy.

SUBJECTS

The subjects included 319 glucose tolerant male individuals, aged 35-60 y.

MEASUREMENTS

Anthropometric parameters (body mass index (BMI) and waist-to-hip ratio (WHR)), fasting concentrations of glucose, insulin, and lipids (total cholesterol, HDL-cholesterol, triglycerides), the sum of glucose levels during 75 g-oral glucose tolerance test (Sigma-OGTT), and systolic and diastolic blood pressure (SBP and DBP, respectively).

RESULTS

The prevalence of obesity was higher among shift workers compared to day workers, whereas body fat distribution was not different between the two groups. Shift workers had higher BMI than day workers, and shift working was associated with BMI, independently of age and work duration. Shift workers had significantly higher SBP levels, which were independently influenced by BMI, but not by shift work, thus suggesting that the difference in SBP may well be mediated by the increased body fatness.

CONCLUSION

In workers of an industry sited in Southern Italy, shift work may be directly responsible for increased body fatness and is indirectly associated with higher blood pressure levels and some features of metabolic syndrome.

Metabolic disturbances in male workers with rotating three-shift work. Results of the WOLF study

OBJECTIVES

The aim of the present study was to investigate the relationship between important metabolic risk factors for coronary heart disease (CHD) and type 2 diabetes in shift workers and day workers.

METHODS

Cross-sectional data from a sub-population in the WOLF study consisting of 665 day workers and 659 three-shift workers in two plants were analysed.

RESULTS

A higher proportion of shift workers than day workers had high triglyceride levels (> or =1.7 mmol/l), low levels of HDL-cholesterol (<0.9 mmol/l) and abdominal obesity (waist/hip ratio>0.9). The risk of low HDL-cholesterol was doubled in shift workers, (odds ratio (OR): 2.02, 95% confidence interval (95% CI): 1.24-3.28) after being adjusted for age, socio-economic factors, physical activity, current smoking, social support and job strain. High levels of triglycerides were also significantly associated with shift work (OR: 1.40, 95% CI: 1.08-1.83). The OR for abdominal obesity was 1.19, (95% CI: 0.92-1.56). The prevalence of hyperglycaemia (serum glucose > or =7.0 mmol/l) was similar in day and shift workers. No significant interaction was seen between shift work and abdominal obesity with regard to the associations with triglycerides and HDL-cholesterol.

CONCLUSIONS

We found a significant association between shift work and lipid disturbances (i.e. low HDL-cholesterol and high triglyceride levels). We did not find any association with hyperglycaemia.

Is there an association between shift work and having a metabolic syndrome? Results from a population based study of 27,485 people

OBJECTIVES

To explore how metabolic risk factors for cardiovascular disease (CVD) differ between shift workers and day workers in a defined population. Shift work has been associated with an increased risk of CVD. Risk factors and causal pathways for this association are only partly known.

METHODS

A working population of 27,485 people from the Västerbotten intervention program (VIP) has been analysed. Cross sectional data, including blood sampling and questionnaires were collected in a health survey.

RESULTS

Obesity was more prevalent among shift workers in all age strata of women, but only in two out of four age groups in men. Increased triglycerides (>1.7 mmol/l) were more common among two age groups of shift working women but not among men. Low concentrations of high density lipoprotein (HDL) cholesterol (men<0.9 and women<1.0 mmol/l) were present in the youngest age group of shift workers in both men and women. Impaired glucose tolerance was more often found among 60 year old women shift workers. Obesity and high triglycerides persisted as risk factors in shift working men and women after adjusting for age and socioeconomic factors, with an OR of 1.4 for obesity and 1.1 for high triglyceride concentrations. The relative risks for women working shifts versus days with one, two, and three metabolic variables were 1.06, 1.20, and 1.71, respectively. The corresponding relative risks for men were 0.99, 1.30, and 1.63, respectively.

CONCLUSIONS

In this study, obesity, high triglycerides, and low concentrations of HDL cholesterol seem to cluster together more often in shift workers than in day workers, which might indicate an association between shift work and the metabolic syndrome.

Changes in frequency of premature complexes and heart rate variability related to shift work

OBJECTIVES

To investigate whether an increased risk of cardiovascular disease might be caused by increased arrhythmogeneity and by unfavourable changes in autonomic cardiac control the changes in the occurrence of premature complexes (PVCs) and in heart rate variability (HRV) were studied in subjects who started to work in shifts.

METHODS

1 Year changes in frequency of PVCs and HRV were measured in 49 shift workers and 22 control subjects working in daytime. All respondents were starting in a new job in integrated circuit or waste incinerator plants.

RESULTS

The incidence of PVC increased significantly in shift workers over the 1 year follow up, compared with daytime workers. The frequency of ventricular extrasystoles increased in 48.9% of the shift workers, and in 27.3% of the daytime workers. The Spearman correlation coefficient between the number of nights worked and the change in PVCs was 0.33 (p=0.004). A small non-significant unfavourable change in HRV was found in both the shift and daytime workers.

CONCLUSIONS

A change in arrhythmogeneity, but not in cardiac autonomic control, might explain the increased risk of cardiovascular disease in shift workers.

Shiftwork and cardiovascular disease: review of disease mechanisms

This paper reviews the main findings concerning mechanisms explaining the increased risk of coronary heart disease (CHD) in shiftworkers. We discuss a conceptual model, in which three main shiftwork pathways to CHD are postulated--social problems, behavioral change, and disturbed circadian rhythm. Social problems that are associated with shiftwork might lead to stress. Significant shiftwork-related behavioral problems are smoking and unhealthy food habits. Disturbed circadian rhythm might result in sleep deprivation. Unphysiologic timing of physical activity and food intake in relation to circadian rhythms is another possible explanation for the negative impact on the cardiovascular system.

Decrease in the time-dependent difference in urinary excretion of furosemide with age

The influence of age on the time-dependent difference in urinary excretion of furosemide, a loop diuretic agent, was examined in this longitudinal study. Male Wistar rats were maintained under conditions of light from 07:00 to 19:00 h and dark from 19:00 to 07:00 h. Furosemide (30 mg/kg) was given orally at 12:00 h (day trial) or 00:00 h (night trial) to rats at 3 months of age, and urine was collected for 8 h after dosage. Thereafter, the identical protocol was repeated using the same animals at 6, 9, 12, 15, 18, and 21 months of age. The urinary excretion of furosemide was significantly greater in the day than in the night trial at 3 months of age. Such a time-dependent difference was observed for up to 15 months, but disappeared at 18 and 21 months of age. The time-dependent difference in urinary excretion of furosemide (day trial - night trial) decreased gradually throughout the observation period of the study. These results suggest that the time-dependent difference in the urinary excretion of furosemide diminishes during the aging process and disappears by 18 months of age in male Wistar rats.

Daily variation in the urinary excretion of furosemide in young and aged rats

We have recently demonstrated that the time-dependent difference in urinary excretion of furosemide, a loop diuretic, diminishes during the aging process and disappears by 18 months of age in rats. The present study was undertaken to examine whether the amplitude of the daily variations in the urinary excretion of furosemide or their pattern, or both, are influenced in aged animals. Young (3 months of age) and aged (30 months of age) Wistar rats were maintained under conditions of light from 7 am to 7 pm and dark from 7 pm to 7 am. Furosemide (30 mg/kg) was given orally at 4 am, 8 am, 12 am, 4 pm, 8 pm or 12 pm. Urine was collected for 8 hours after furosemide administration and urinary excretion of furosemide was determined. There were significant daily variations in the urinary furosemide and the urine volume with the peak at 8 am and the trough at 12 pm in both groups of rats. The differences in these parameters between the 8 am and 12 pm trials were significantly smaller in the aged than in the young rats. These results suggest that the age-related alteration in the time-dependent phenomenon of furosemide is caused by the decreased amplitude of the daily variation in the urinary furosemide excretion and its diuretic effect.

Influence of clorgyline treatment on chronopharmacology of furosemide in rats

Circadian variations in the adrenergic nervous system have been reported to be altered by chronic treatment with clorgyline, a monoamine-oxidase inhibitor. In the present study, the influence of clorgyline on the chronopharmacology of furosemide, a loop diuretic agent, was examined in rats maintained under conditions of light from 7 am to 7 pm and dark from 7 pm to 7 am. Clorgyline (4 mg/kg/day) or its vehicle alone was infused subcutaneously by osmotic minipumps for 14 days. Furosemide (30 mg/kg) was given orally at 12 am [noon (N)] or 12 pm [midnight (M)]. Urine was collected for 8 hours after the agent, and urinary excretions of sodium and furosemide were determined. Urine volume and urinary excretions of sodium and furosemide were significantly greater at 12 N than at 12 M in the vehicle-infused group of rats. However these administration time-dependent changes in the effects of furosemide and its urinary excretion disappeared in the clorgyline-infused animals. These results suggest that the mode of the diurnal variation in the effects of furosemide is altered by chronic treatment with clorgyline. As chronic clorgyline is considered to disturb the adrenergic nervous system, the present findings are compatible with the hypothesis that this system is involved in the mechanism responsible for the time-dependent change in the effects of furosemide.

Daily variation in the effects of furosemide in rats

Daily variation in the effects of furosemide, a loop diuretic agent, was examined in Wistar rats maintained under conditions of light from 7 a.m. to 7 p.m. and dark from 7 p.m. to 7 a.m. Furosemide (30 mg/kg) was given orally at 12 p.m., 4 a.m., 8 a.m., 12 a.m., 4 p.m. or 8 p.m. Urine was collected for 8 hr after furosemide administration, and urinary excretions of sodium and furosemide were determined. There were significant daily variations in the urine volume and urinary excretions of sodium and furosemide with a peak at 8 a.m. and a trough at 12 p.m. Significant correlations were observed between the urinary amount of furosemide and its diuretic effects (urine volume and urinary sodium excretion). These results suggest that the diuretic effects of furosemide show daily variations which are, at least in part, caused by the daily variation in the urinary excretion of furosemide.

Increased triglyceride levels in shift workers

PURPOSE

To assess an independent relationship between shift work and serum lipid levels.

DESIGN

Cross-sectional survey.

SETTING

Two plants of northern France: a chemical one and a nuclear power station.

PARTICIPANTS

All the shift workers of the chemical plant and of one part of the nuclear station. One hundred nine persons were selected, 25 were excluded or absent during the study, and 11 refused to participate. Day workers matched with shift workers according to age, educational level, birthplace, and occupational physical activity level served as controls; 109 were selected, 26 were excluded or absent, and 10 refused to participate.

MAIN OUTCOME MEASURES

Fasting venous plasma concentration of total cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol; dietary intake assessed by a 3-day record, smoking habits, and body mass index (BMI).

RESULTS

Shift workers had significantly higher levels of serum triglyceride (1.26 versus 1.03 mmol/L, p = 0.01). Cholesterol and HDL cholesterol levels were similar for the two groups. There was no difference in energy and nutrient intake, but day workers had a higher alcohol intake (15.64 g/d versus 9.3 g/d, p = 0.03). Multivariate analysis conducted with triglycerides as dependent variable and shift work, BMI, smoking, age, leisure time physical activity level, energy intake, and alcohol intake as independent variables confirmed that shift work has a significant explanatory power for triglyceride levels (beta = 0.134, p = 0.0005).

CONCLUSION

This study confirms that shift work is associated with an increase of triglyceride levels independent of dietary intake. We did not find any influence of shift work on cholesterol and HDL cholesterol. Despite this latter fact, our findings are to be considered in the explanation of coronary risk among shift workers. Further studies are needed to elucidate the mechanism of this relative hypertriglyceridemia: stress induced by shift work or diurnal rhythm disturbances.

Chronopharmacological study of furosemide; (VIII) influence of feeding restriction

We have previously reported that a time-dependent variation is observed in the diuretic effect of furosemide and the light-dark cycle is a potent zeitgeber for this chronopharmacological phenomenon of the agent in rats. The present study was undertaken to examine whether a time of food intake is another zeitgeber for this event. In study I, rats were maintained with free access to food for 3 weeks. Furosemide (30 mg/kg) was given orally at 12 am or 12 pm. Urine was collected for 8 hours after the agent and urinary excretion of sodium and furosemide were determined. Thereafter, these rats were maintained under a daytime-restricted feeding schedule (9 am-11 am) for 3 weeks (study II) and a night-time-restricted feeding schedule (9 pm-11 pm) for 3 weeks (study III). The identical protocol of study I was repeated at the end of study II and III. Diuretic effect of furosemide and its urinary excretion were significantly greater at 12 am than at 12 pm in study I and III. However such an administration time-dependent change in the effect of furosemide and its urinary amount disappeared in study II. These data indicate that a time of food intake is another potent zeitgeber for the time-dependent variation in the diuretic effect of furosemide.

Chronopharmacological study of furosemide; (VI). Influence of prolonged exposure to continuous light

We have previously reported that a time-dependent variability is observed in the diuretic effects of furosemide in rats. The present study was undertaken to examine the influence of prolonged exposure to continuous light on chronopharmacological profiles of furosemide in Wistar rats. In study I, rats were maintained for more than 2 weeks under conditions of light (0700-1900 hrs) and dark (1900-0700 hrs) (L-D). Furosemide (30 mg/kg) was orally given at 1200 hrs or at 2400 hrs. Urine was collected for 8 hours after the drug and urinary excretion of sodium and furosemide were determined respectively. Thereafter, these rats were exposed to continuous light (L-L) for the next 4 weeks, and were again maintained under the L-D cycle. The identical trial of study I was repeated at the end of the L-L (study II) and the second L-D (study III) conditions. Urine volume and urinary excretion of sodium and furosemide following the drug were significantly greater at 1200 hrs than at 2400 hrs under conditions of L-D (study I and III). However these administration time-dependent changes in the effects of furosemide and its urinary amount disappeared with L-L condition (study II). These findings indicate that the mode of the time-dependent changes in the effects of furosemide is altered by prolonged exposure to continuous light.

Increased risk of ischaemic heart disease in shift workers

504 papermill workers were followed up for 15 years and the incidence of ischaemic heart disease (IHD) in shift workers was compared with that in day workers. The relative risk (RR) of IHD rose with increasing duration of reported exposure to shift work. A significant risk of IHD was associated with an exposure of 11 - 15 years (RR = 2.2, p less than 0.04) and of 16 to 20 years (RR = 2.8, p less than 0.03. The association was independent of age and smoking history. The RR of IHD fell sharply after 20 years of shift work. This was ascribed to the pronounced positive selection that had taken place in this group.

The effect of recent life events stress, life assets, and temperament pattern on cardiovascular risk factors for Akron City police officers

Police officers, as a group, experience many occupational demands with physiological and psychological effects that could be harmful to their health. A primary objective of this study was to analyze specific behavioral and physiological risk factors that could lead to hypertension and accelerated coronary artery disease. Three hundred thirty-one male Akron City police officers participated in the study. A group of volunteer males (n = 48) who worked in city clerical jobs were used as controls. Questionnaires were administered in order to measure such behavioral variables as recent life change, life assets, and temperament pattern. Blood chemistry and physiological variables were also measured. The police officers had higher diastolic blood pressure (DBP), norepinephrine (NE) levels, and recent life change unit (LCU) scores than the control group. Increased hostility and depression scores were associated with higher DBP and recent LCU scores and lower life asset unit (LAU) scores. Individuals with higher "dominant" scores and moderate to high recent LCU scores had higher cardiovascular risk factors than those with moderate to high recent LCU scores who were ranked as "subordinate." Rotating shift workers had abnormally elevated NE levels, which, if not controlled, may lead to higher cardiovascular risk. Behavioral intervention programs have been introduced with the goals of reducing stress, increasing life assets, and teaching relaxation techniques.

Hormonal and cardiovascular variations during a public lecture

A long-time electrocardiogram over a period of 12 h was recorded from ten test persons without cardiovascular diseases, and their blood pressure was checked at regular intervals on the day of a public speech. In order to determine plasma concentrations of epinephrine, norepinephrine, cortisol, human growth hormone (hGH), prolactin and gastrin, blood samples were taken from the subjects by inserting a venous catheter in the morning. The levels of epinephrine, norepinephrine and cortisol were also examined in urine collected from the volunteers. During the public speech there was a distinct increase in blood pressure and pulse rate. Epinephrine and cortisol showed the clearest increase in serum and collected urine, whereas norepinephrine, prolactin, hGH and gastrin reacted less strongly. The epinephrine/norepinephrine ratio value is discussed as a parameter for psychomental and emotional strain.

Pathogenic life changes in middle adulthood and coronary heart disease: a life-span developmental perspective

Empirical evidence is reviewed about the contributions of life changes and the coronary-prone behavior pattern in the development of myocardial infarction in middle adulthood. Since established clinical risk factors account for about half of the total variance, it is necessary to explore in more detail the crucial developmental role that distressing psychologic and social parameters should play. Because of the generally prolonged incubation period of the effects of psychosocial risk factors, it is proposed that they should be studied from a life-span developmental perspective. Two metamodels seem appropriate in this respect: a mechanistic model by Dohrenwend and Dohrenwend, and an organismic model by Levinson. After scrutinizing some properties of these models, including their potential explanatory power, it is argued that an organismic model may predict better the pathogenic development of distressing psychosocial risk constellations over consecutive phases in the life course of the heart patient.

Job characteristics of occupations and myocardial infarction risk:effect of possible confounding factors

In this paper some previously found associations between psychosocial occupational characteristics and myocardial infarction (MI) risk are scrutinized regarding confounding effects. Standardized occupational characteristics were obtained for 118 occupational groups by means of a nation wide interview survey (3876 men). Possible confounding factors available were smoking, low level of education, high proportion of immigrants (mainly of Finnish origin) and heavy lifting. The standardized characteristics were utilized in a case-control study of 1216 men 40-64 years of age, living in the Stockholm County. It was concluded that occupations characterized by both high demand and at the same time small possibility of control or growth ('strain') are associated with an elevated MI risk regardless of the confounding factors. Taking each of the confounding factors into account the risk of developing MI for men aged 40-54 years employed in these strenuous occupations is about twice as high as for those employed in other occupations.