Subjective poor sleep and white blood cell count in male Japanese workers

Shift Work is Associated with an Elevated White Blood Cell Count: A Systematic Review and Meta-Analysis

The white blood cell (WBC) count increases significantly in reaction to infections and certain chronic diseases. Shift employment increases the risk for chronic low-grade inflammation and the progression of several chronic diseases. The objective of this study was to systematically evaluate the evidence from studies on total and differential WBC counts in shift employees. A literature search was performed in PubMed®, Web of Science, and Scopus databases using keywords for research published before March 1, 2022. A meta-analysis was conducted for total and differential WBC counts using a random-effects approach. A total of 25 studies covering a sample of 37,708 day and shift employees were included in this review. The studies represented America, Europe, East Asia, and Middle East. A significant increase in the total counts (×109/L) of WBC [mean difference (MD) = 0.43; 95% confidence interval (CI): 0.34-0.52; P < 0.001], lymphocytes (MD = 0.16; 95% CI: 0.02-0.30; P = 0.02), monocytes (MD = 0.04; 95% CI: 0-0.07; P = 0.03), and eosinophils (MD = 0.01; 95% CI: 0-0.01; P = 0.03) was observed in shift workers compared to the day counterparts. However, neutrophils and basophils were not significantly different between the groups. Shift work significantly increases the total and differential blood counts in peripheral circulation. Therefore, total and differential WBC counts represent a relatively inexpensive biomarker for diagnostics and prognostics of diseases in shift workers.

Chrono-modulated effects of external stressors on oxidative stress and damage in humans: A scoping review on night shift work

BACKGROUND

Oxidative stress and tissue damage (OSD) play a pivotal role as an early-stage process in chronic disease pathogenesis. However, there has been little research to better understand the temporal (χρόνος[chronos]) dimensions of OSD process associated with environmental (non-genetic, including behaviors/lifestyle) and/or occupational stressors, like night shift work. OSD processes have recently attracted attention in relation to time-resolved external stressor trajectories in personalized medicine (prevention) initiatives, as they seem to interact with circadian clock systems towards the improved delineation of the early stages of (chronic) disease process.

OBJECTIVES

This work critically reviewed human studies targeting the temporal dynamics of OSD and circadian clock system's activity in response to environmental/occupational stressors; the case of night shift work was examined.

METHODS

Being a key stressor influencing OSD processes and circadian rhythm, night shift work was evaluated as part of a scoping review of research in OSD, including inflammatory and metabolic processes to determine the extent of OSD research undertaken in human populations, methodologies, tools and biomarkers used and the extent that the temporal dimensions of exposure and biological effect(s) were accounted for. Online databases were searched for papers published from 2000 onwards, resulting in the selection of 53 original publications.

RESULTS AND DISCUSSION

The majority of studies (n = 41) took place in occupational settings, while the rest were conducted in the general population or patient groups. Most occupational studies targeted outcomes of oxidative stress/damage (n = 19), followed by the combination of OSD with inflammatory response (n = 10), and studies focused on metabolic outcomes (n = 12). Only a minor fraction of the studies measured biomarkers related to circadian rhythm, such as, melatonin, its metabolite, or cortisol. Night shift work was associated with select biomarkers of OSD and inflammation, albeit with mixed results. Although much progress in delineating the biological mechanisms of OSD process has been made, an equally thorough investigation on the temporal trajectory of OSD processes as triggered by environmental/occupational stressors in human studies has yet to fully evolve.

Mechanism of the association between sleep quality and mortality in middle-aged and older adults: A prospective study analysis of the UK Biobank

BACKGROUND

Although sleep quality is known to be associated with mortality, how poor sleep quality contributes to an increased risk of mortality is still unknown. We aimed to examine whether lifestyle, psychosocial and biological factors mediate the association.

METHODS

205,654 participants from UK Biobank were used for the analysis. The outcome was all-cause, cardiovascular disease (CVD) and cancer mortality by February 2022. Exposure was assessed by a sleep score consisting of five sleep behaviors at baseline. Lifestyle, psychosocial, and biological factors are regarded as potential mediators. Mediation analysis based on Cox proportional hazards models was performed.

RESULTS

Poor sleep quality was associated with a higher risk of all-cause (Hazard Ratio [HR] = 1.098; 95% CI: 1.058-1.140), CVD (HR = 1.139; 95% CI: 1.045-1.243) and cancer mortality (HR = 1.095; 95% CI: 1.040-1.152). Lifestyle mediators (smoking, physical activity, sedentary, BMI and diet) could explain between 2.6% and 34.0% of the increased risk of all-cause mortality in individuals with poor sleep quality. Self-reported health, frailty, depression, and loneliness were significant psychosocial mediators of this association pathway. About one-fifth of the association can be explained by the biological role of CRP. Similar mediating patterns were observed for CVD and cancer mortality.

LIMITATIONS

Both exposure and mediators were measured at baseline, so the possibility of reverse causality cannot be ruled out.

CONCLUSIONS

Poor sleep quality is associated with an increased risk of death through a combination of lifestyle, psychosocial and biological pathways. Adopting healthy lifestyles and staying psychosocial well-being are cost-effective interventions to lower the risk of death.

Sleep quality and sleep-related issues in industrial workers: a global meta-analysis

Objectives. Sleep-related issues are important health issues. This study aimed to investigate the global prevalence of sleep-related issues in industrial workers. Methods. A syntax of keywords was used to search the PubMed, Web of Science and Scopus databases. The search time was limited to articles published until September 2020, and the search range was in English. Events and samples were extracted for each study to calculate the prevalence. For all subgroups, events and samples were extracted to calculate the results of the subgroups. The random-effects method was used in the analysis. Heterogeneity was examined at the levels of all analyses. Results. Forty-eight articles were included in the analysis as eligible studies. Sleep-related issues have 30% prevalence in the 95% confidence interval (CI) [25, 35%]. The prevalence of sleep-related issues in men was 38%, 95% CI [31, 45%] and in women was 32%, 95% CI [14, 50%]. The prevalence of poor sleep quality, insomnia, sleep duration <7 h, snoring and sleepiness was 36, 22, 37, 29 and 10%, respectively. Conclusions. Sleep-related issues have a high prevalence in industrial workers, and the cause of these differences needs to be addressed and increasing insights provided to prevent and treat sleep disorders.

Examining the role of systemic chronic inflammation in diet and sleep relationship

BACKGROUND

It is well known that systemic chronic inflammation (SCI), which can be modulated by diet, is associated with poor sleep outcomes. However, the role of SCI in diet health and sleep quality relationship has not been well established.

METHODS

Here, by using the UK Biobank data set, we assessed the association between markers of SCI (leukocyte, platelet, lymphocyte, neutrophil, and basophil counts; C-reactive protein levels and neutrophil to lymphocyte ratio (NLR)), habitual intake of food groups, diet health and sleep quality in 449,084 participants. We also formally tested the possibility that SCI might mediate the relationship between diet health and sleep quality.

RESULTS

Our results revealed (i) negative associations between SCI and food groups that are abundant in healthy diets (fruit, vegetable and oily and non-oily fish) and (ii) positive associations between SCI and food groups that are abundant in unhealthy diets (processed meat). Sleep quality was also negatively associated with platelet counts, CRP levels and NLR. Crucially, however, while platelet and neutrophil counts, CRP levels and NLR fully mediated the association between diet health and sleep quality, leukocyte, lymphocyte and basophil counts partially mediated the associations between diet health and sleep quality.

CONCLUSION

Reducing SCI via dietary interventions could be an effective primary and/or complementary strategy to increase sleep quality. Further interventional trials are warranted to (i) establish the strength of associations, preferably by using validated diet and sleep measures and (ii) examine longer term effects of anti-inflammatory diets on sleep-, diet- and inflammation-related health outcomes.

Sleep disturbance, neuro-immune markers, and depressive symptoms in older age: Conditional process analysis from the English Longitudinal Study of Aging (ELSA)

This study aimed to investigate the long-term association between subjective sleep disturbance and depressive symptoms in older adults, and ascertain whether this association is partially mediated by neuro-immune markers, while testing the moderation of sex using conditional process analyses, i.e., combinations of mediation and moderation analyses. We analysed data of 2124 participants aged 50 and above from the English Longitudinal Study of Ageing (ELSA) across three waves of data collection. Sleep disturbance was assessed in 2008/9, serum levels of high sensitivity C-reactive protein (hs-CRP), insulin like growth factor-1 (IGF-1), white blood cell (WBC) count in 2012/2013, and self-reported depressive symptoms in 2016/2017. After accounting for health-related and psychosocial confounders, results showed that sleep disturbance significantly predicted depressive symptoms at follow-up in the whole sample and hs-CRP in women, but not in men. Hs-CRP also predicted depressive symptoms only in women. Moreover, hs-CRP significantly mediated the association between sleep disturbance and depressive symptoms in women, but not in men. The association between sleep disturbance and IFG-1was marginal, and the latter did not mediate the association between sleep and depressive symptoms neither in women nor in men. Results on WBC count were all non-significant. In conclusion, sleep disturbance resulted significantly associated with depressive symptoms in a long-term follow-up. Moreover, ELSA data provide preliminary evidence that increased inflammation may mediate this association in women. Future longitudinal studies may advance the knowledge in the field considering the mediating role of proinflammatory cytokines such as interleukin-6.

Workability, quality of life and cardiovascular risk markers in aging nightshift workers: a pilot study

Background

In aging healthcare professionals, multiple stressors such as night work may affect life and work satisfaction and risk for chronic diseases (e.g. cardiovascular disease [CVD]). In this pilot study we compared workability, quality of life (QoL), and CVD risk markers between night shift and day workers.

Methods

We included 70 hospital employees (mean age 52 ± 4 years, 91.4% female): 32 rotating night shift workers (> 3 nights/month) and 38 permanent day workers. In addition to sociodemographic, lifestyle, and sleep characteristics, we assessed i) workability index (WAI), ii) QoL (World Health Organization Quality of Life [WHOQOL-Bref]) and iii) CVD risk markers, i.e. carotid ultrasound measurements, and biomarkers (NTproBNP, CRP, IL‑6, LDL, ferritin, copper, zinc, and selenium). WAI, QoL, and CVD risk markers were compared between night and day workers. In a subgroup of participants (N = 38) with complete data, we used quantile regression analysis to estimate age and multivariate adjusted differences in biomarker levels.

Results

We found no differences in the domains of QoL (physical health, psychological, social relationships, and environment) and WAI scores between night and day workers. Night shift workers were less likely to report excellent workability than day workers, although differences were not statistically significant. Night shift workers reported more sleep problems (73.1% vs. 55.6%) and tended to have lower zinc levels and higher inflammatory markers (CRP, IL‑6, ferritin), but differences were not significant after adjusting for potential confounders.

Conclusions

Workability, QoL and CVD markers did not significantly differ between rotating night shift and day workers in this small pilot study. Sleep problems and inflammatory marker levels carry implications for occupational health.

Supplementary Information

The online version of this article (10.1007/s00508-021-01928-6) contains supplementary material, which is available to authorized users.

Prevalence of current and former smoking in industrial workers worldwide: a systematic review and meta-analysis

OBJECTIVES

One of the health problems in recent decades is the prevalence of smoking in the world. In this study, the global prevalence of smoking in industrial workers was investigated using meta-analysis.

METHOD

The method of the present study was a systematic review and meta-analysis. Three scientific sources, PubMed, Web of Science, and Scopus, were selected for the search, and these databases were searched until September 2020. Random effects method was used for the analysis and then the analysis was performed for the type of smoking (Current, Former), gender, and continent. Heterogeneity was examined in all analyses.

RESULT

A total of 88 studies were included in the meta-analysis. The prevalence of smoking in industrial workers was 41% also the confidence interval was 35-48%. The prevalence of current smoking in industrial workers was 39% also the confidence interval was 29-48%. The prevalence of former smoking in industrial workers was 18% also the confidence interval was 13-22%. I² heterogeneity test was 99.9%.

DISCUSSION

From the findings of the present study, it can be seen that industrial workers are more exposed to smoking compared to the general population, and this can put their health at greater risk.

The mediating role of sleep, physical activity, and diet in the association between shift work and respiratory infections

Objectives:

Shift work may be associated with an increased incidence of respiratory infections. However, underlying mechanisms are unclear. Therefore, our aim was to examine the mediating role of sleep, physical activity, and diet in the association between shift work and respiratory infections.

Methods:

This prospective cohort study included 396 shift and non-shift workers employed in hospitals. At baseline, sleep duration and physical activity were measured using actigraphy and sleep/activity diaries, sleep quality was reported, and frequency of meal and snack consumption was measured using food diaries. In the following six months, participants used a smartphone application to report their influenza-like illness/acute respiratory infection (ILI/ARI) symptoms daily. Mediation analysis of sleep, physical activity, and diet as potential mediators of the effect of shift work on ILI/ARI incidence rate was performed using structural equation modeling with negative binomial and logistic regression.

Results:

Shift workers had a 23% [incidence rate ratio (IRR) 1.23, 95% CI 1.01–1.49] higher incidence rate of ILI/ARI than non-shift workers. After adding the potential mediators to the model, this reduced to 15% (IRR 1.15, 95% CI 0.94–1.40). The largest mediating (ie, indirect) effect was found for poor sleep quality, with shift workers having 29% more ILI/ARI episodes via the pathway of poorer sleep quality (IRR 1.29, 95% CI 1.02–1.95).

Conclusions:

Compared to non-shift workers, shift workers had a higher incidence rate of ILI/ARI that was partly mediated by poorer sleep quality. Therefore, it may be relevant for future research to focus on perceived sleep quality as an underlying mechanism in the relation between shift work and increased infection susceptibility.

Time- and Race-Specific Haematological Reference Intervals for Healthy Volunteer Trials: A Retrospective Analysis of Pooled Data From Multiple Phase I Trials

Most UK hospitals, laboratories, and research institutions use uniform reference intervals (RI) that do not take into account known diurnal and racial variation in total white blood cells (WBC) count and its constituent parameters. These risks of excluding potentially suitable ethnic minority volunteers from participating in phase I clinical trials could call into question the validity of a trial’s findings or limit its scientific applications and ability to accurately observe drug effects upon WBC parameters. This study pools data from multiple phase I trials, assesses the effects of race and time of day on WBC count, and compares it to the existing literature to establish race and time-specific RIs. A total 13,332 venous blood samples obtained from 7,157 healthy male and female volunteers at the time of screening or admission (predosing) who took part in 35 phase I trials over a period of seven years were pooled and the data were analyzed using generalised estimating equation models. Adjusted RI of total WBC count and its individual parameters were then calculated according to time of day (morning vs. evening) for both black and nonblack populations. This study indicates that black individuals on average had lower total WBC, neutrophil, monocyte, eosinophil, and basophil counts than individuals from nonblack racial groups. Black volunteers had higher mean lymphocyte counts relative to their nonblack counterparts. These differences were deemed statistically significant. Statistically significant increases in total WBC, neutrophil, lymphocyte, and monocyte counts were also observed over the course of daily sampling. Eosinophil counts decreased during this time period, but this finding was only statistically significant in the nonblack population. Despite an observed mild diurnal increase in basophil count in both populations, this was not considered statistically significant. This high-powered study adds significant weight to the known evidence for diurnal and racial variation in WBC parameters. Importantly, it proposes specific RIs that more precisely reflect race and time of day. These could ensure increased participation of black volunteers in clinical trials for improved population representation. Furthermore, the proposed RIs allow for more accurate postdose safety monitoring and reporting, and ensure improved monitoring of postdose WBC count changes.

Immunological effects of shift work in healthcare workers

The immune system potentially plays an important mechanistic role in the relation between shift work and adverse health effects. To better understand the immunological effects of shift work, we compared numbers and functionality of immune cells between night-shift and non-shift workers. Blood samples were collected from 254 night-shift and 57 non-shift workers employed in hospitals. Absolute numbers of monocytes, granulocytes, lymphocytes, and T cell subsets were assessed. As read out of immune function, monocyte cytokine production and proliferative capacity of CD4 and CD8 T cells in response to various stimuli were analysed. The mean number of monocytes was 1.15 (95%-CI = 1.05–1.26) times higher in night-shift than in non-shift workers. Furthermore, night-shift workers who worked night shifts in the past three days had a higher mean number of lymphocytes (B = 1.12 (95%-CI = 1.01–1.26)), T cells (B = 1.16 (95%-CI = 1.03–1.31)), and CD8 T cells (B = 1.23 (95%-CI = 1.05–1.45)) compared to non-shift workers. No differences in functional parameters of monocytes and lymphocytes were observed. The differences in numbers of monocytes and T cells suggest that chronic exposure to night-shift work as well as recent night-shift work may influence the immune status of healthcare workers. This knowledge could be relevant for preventive initiatives in night-shift workers, such as timing of vaccination.

Shift Work and Leukocyte Count Changes among Workers in Bangkok

OBJECTIVES

Previous epidemiological evidence for the association of shift work exposure and increased leukocyte count is cross-sectional in nature, thus limiting cause-effect inference. We therefore used a longitudinal design to: (i) compare leukocyte counts at baseline between shift and day workers and (ii) examine the time trend of leukocyte counts over the follow-up period for these workers.

METHODS

A retrospective cohort study was conducted among 6737 workers aged <60 years at two large organizations (a humanitarian organization and a university) in Bangkok, Thailand who had participated in at least two annual health check-ups during the period 2005-2016. Shift work exposure history was assessed by a self-administered questionnaire and categorized into day, former, and current shift workers. Data on leukocyte count were collected annually as part of worksite health screening during the observation period. Association of shift work exposure and increased leukocyte count was then examined cross-sectionally and longitudinally by using multiple linear regression and multilevel analysis of repeated measures data, respectively. In addition, trends for leukocyte count over the follow-up period and work years were examined using LOWESS smooth curves.

RESULTS

Compared to day work, the current shift work was associated with increased leukocyte counts. The magnitude of percentage increase was the highest for basophil counts, followed by eosinophil and lymphocyte counts. Both cross-sectional and longitudinal evidence revealed this association, although it was less pronounced longitudinally. For total leukocyte count, the magnitude of difference was constant across the 11-year follow-up period. However, for lymphocyte and basophil counts, these discrepancies tapered over the work years until they no longer differed (for lymphocyte count) or even differed in the opposite direction (for basophil count) in later work years.

CONCLUSION

This study confirmed previous cross-sectional evidence that shift work exposure-increased leukocyte counts and that this was reversible. Whether this increase in immune cell count also results in an increased immune cell activity and serves as the intermediary in the association between shift work exposure and subsequent chronic disease development needs further investigation.

The Sleep-Immune Crosstalk in Health and Disease

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Association between lifestyle and hematological parameters: A study of Chinese male steelworkers

Background

Increasing evidence suggests an association between lifestyle and white blood cell (WBC) count; however, no study has examined the effects of lifestyle associations on hematological parameters. The aim of this study was to examine the association between lifestyle factors and hematological parameters in a large population‐based sample of Chinese male steelworkers.

Methods

This study included 3189 male workers at a steel plant who responded to a cross‐sectional questionnaire on basic attributes, lifestyle, and sleep. All workers in the plant underwent periodic health checkups. Hematological parameters were also examined at the checkup.

Results

Stepwise linear regression analyses showed that smoking, poor sleep, shift work, and obesity were all significant factors associated with WBC count. Obesity was independently associated with RBC count. Furthermore, smoking and obesity were associated with hemoglobin, and smoking, poor sleep, and obesity were independently associated with hematocrit. Moreover, smoking was the main factor associated with MCV and MCH. When the subjects were divided into quartiles according to WBC count, RBC count, hemoglobin, hematocrit, MCV, MCH, and increased WBC count were associated with smoking, poor sleep, shift work, and obesity. Increased hemoglobin was associated with smoking and obesity. Furthermore, an increased RBC count was associated with obesity, and increased hematocrit was associated with smoking, poor sleep, and obesity. Similarly, increased MCV and MCH were also associated with smoking.

Conclusion

This study indicates that lifestyle factors may exert an important effect on hematological parameters (eg, WBC count, RBC count, hemoglobin, hematocrit, MCV, and MCH).

Shiftwork and Biomarkers of Subclinical Cardiovascular Disease: The BCOPS Study

OBJECTIVE

To assess the association of shiftwork with biomarkers of subclinical cardiovascular disease and examine the moderating role of body mass index (BMI) in a police cohort.

METHODS

A cross-sectional analysis was conducted among officers who were categorized as working the day, evening, or night shift. Comparisons with inflammatory biomarkers were performed among shifts using analysis of variance/covariance and further stratified by BMI to assess potential effect modification.

RESULTS

Associations were observed between day and night shiftworkers for leukocytes, tumor necrosis factor alpha, and homocysteine. After BMI stratification, higher c-reactive protein (CRP) levels were observed among evening shiftworkers with a BMI more than or equal to 30 kg/m versus the day shift.

CONCLUSIONS

Future studies examining prospective changes in these markers will allow for more comprehensive evaluation of their association with shiftwork.

Meeting Sleep Guidelines Is Associated With Better Health-Related Quality of Life and Reduced Premature All-Cause Mortality Risk

PURPOSE

To examine whether meeting sleep guidelines (7-9 hours/night) is associated with better health-related quality of life (HRQOL) and reduced all-cause mortality risk.

DESIGN

Prospective cohort study.

SETTING

2005 to 2010 National Health and Nutrition Examination Survey.

PARTICIPANTS

A total of 13 423 adults.

MEASURES

Sleep duration and HRQOL were assessed from self-report; covariates assessed via survey, examination, and laboratory data; and mortality assessed through 2011 via matching from the National Death Index.

ANALYSIS

Cox proportional hazard regression and ordinal logistic regression.

RESULTS

After adjusting for age, gender, race-ethnicity, body mass index, education, smoking, white blood cell level, iron level, red blood cell distribution width, mean platelet volume, blood pressure, diabetes, coronary artery disease, physical activity, and depression, those meeting sleep guidelines had an 19% reduced risk of premature all-cause mortality (hazard ratio = 0.81; 95% confidence interval [CI]: 0.67-0.99; P = .04). After adjustments, those meeting sleep guidelines had better HRQOL (β = -0.30; 95% CI: -0.38 to -0.21; P < .001). Results for the ordinal regression and Cox proportional analyses were similar in unadjusted and minimally adjusted models.

CONCLUSION

Obtaining optimal levels of sleep is associated with better HRQOL and reduced premature mortality risk, independent of demographic, behavioral, and biological conditions. These findings underscore the importance of achieving optimal levels of sleep.

Relationship between shift work and peripheral total and differential leukocyte counts in Chinese steel workers

OBJECTIVES

Even though shift work has been suspected to be a risk factor for cardiovascular disease, little research has been done to determine the logical underlying inflammation mechanisms. This study investigated the association between shift work and circulating total and differential leukocyte counts among Chinese steel workers.

METHODS

The subjects were 1,654 line workers in a steel plant, who responded to a cross-sectional survey with a questionnaire on basic attributes, life style, and sleep. All workers in the plant received a periodic health checkup. Total and differential leukocytes counts were also examined in the checkup.

RESULTS

Shift workers had higher rates of alcohol use, smoking, poor sleep, poor physical exercise, and obesity than daytime workers. In further analysis, we found that the peripheral total WBC, monocyte, neutrophil, and lymphocyte counts were also greater in shift workers than in daytime workers. When subjects were divided into quartiles according to total WBC, neutrophil, monocyte, and lymphocyte counts, increased leukocyte count was associated with shift work. Using stepwise linear regression analysis, smoking, obesity, and shift work were independently associated with total WBC, monocyte, neutrophil, and lymphocyte counts.

CONCLUSIONS

This study indicates that peripheral total and differential leukocyte counts are significantly higher in shift workers, which suggests that shift work may be a risk factor of cardiovascular disease. Applicable intervention strategies are needed for prevention of cardiovascular disease for shift workers.

A pilot study examining if satisfaction of basic needs can ameliorate negative effects of shift work

The objective of the present study was to investigate if satisfaction of the basic needs of autonomy, competence, and relatedness is related to shift work tolerance, specifically physical and mental fatigue, insomnia, and digestive troubles in a sample of shift workers. This is a cross-sectional pilot questionnaire study, including 252 shift workers employed in a municipality in Norway. Autonomy was negatively related to physical fatigue and digestive troubles, while competence was negatively related to mental fatigue. Relatedness showed significant correlations with insomnia and mental fatigue, but did not reach significance in the regression model controlling for the two other basic needs as well as work scheduling, night work exposure, and sleep medication. Sleep medication was significant in the final regression model for insomnia, but unrelated to fatigue and digestive troubles. The demographic variables, work hours per week, work schedule, and night work exposure were unrelated to all four measures of shift work tolerance. Autonomy and competence may be more important for fatigue and digestive troubles among shift workers than work arrangement variables, night work exposure, and sleep medication use.

Effect of long-term sleep restriction and subsequent recovery sleep on the diurnal rhythms of white blood cell subpopulations

While acute modifications of sleep duration induces a wide array of immune function alterations, less is known of how longer periods with insufficient sleep affect immune functions and how they return to normal once recovery sleep is obtained. The purpose of the present study was to investigate the effects of five days of restricted sleep and a subsequent 7-day period of sleep recovery on white blood cell (WBC) subpopulation count and diurnal rhythms. Nine healthy males participated in a sleep protocol consisting of two baseline days (8h of sleep/night), five nights with restricted sleep (4h of sleep/night) and seven days of recovery sleep (8h of sleep/night). During nine of these days, blood was drawn hourly during night-time end every third hour during daytime, and differential WBC count was analyzed. Gradual increase across the days of sleep restriction was observed for total WBC (p<.001), monocytes (p<.001), neutrophils (p<.001) and lymphocytes (p<.05). Subsequent recovery sleep resulted in a gradual decrease in monocytes (p<.001) and lymphocytes (p=.001), but not in neutrophils that remained elevated over baseline level at the end of the 7-day recovery period. These effects were associated with altered diurnal rhythms of total WBC and neutrophils, restricted sleep being associated with higher levels during the night and at awakening, resulting in a flattening of the rhythm. The diurnal alterations were reversed when recovery sleep was allowed, although the amplitude of total WBC, neutrophils and monocytes was increased at the end of the recovery period in comparison to baseline. Altogether, these data show that long-term sleep restriction leads to a gradual increase of circulating WBC subpopulations and alterations of the respective diurnal rhythms. Although some of the effects caused by five days of restricted sleep were restored within the first days of recovery, some parameters were not back to baseline even after a period of seven recovery days.

Association of psychological stress response of fatigue with white blood cell count in male daytime workers

Relationships between work-related psychological and physical stress responses and counts of white blood cells (WBCs), neutrophils, and lymphocytes were investigated in 101 daytime workers. Counts of WBCs and neutrophils were positively associated with smoking and inversely correlated with high density lipoprotein (HDL)-cholesterol levels. Additionally, general fatigue score as measured by the profile of mood state was positively correlated with WBC and neutrophil counts whereas lymphocyte counts was not significantly associated with fatigue score. Multiple regression analysis showed that WBC count was significantly related to general fatigue, age, and HDL-cholesterol levels. Neutrophil count was significantly related to HDL-cholesterol levels and fatigue score. Among various psychological stress response variables, general fatigue may be a key determinant of low-grade inflammation as represented by increases of WBC and neutrophil counts.

A Biochip with a 3D microfluidic architecture for trapping white blood cells

We present a microfluidic biochip for trapping single white blood cells (WBCs). The novel biochip, microfabricated using standard surface micromachining processes, consists of an array of precisely engineered microholes that confine single cells in a tight, three dimensional space and mechanically immobilize them. A high (> 87%) trapping efficiency was achieved when WBC-containing samples were delivered to the biochip at the optimal pressure of 3 psi. The biochip can efficiently trap up to 7,500 cells, maintaining a high trapping efficiency even when the number of cells is extremely low (~200 cells). We believe that the developed biochip can be used as a standalone unit in a biology/clinical lab for trapping WBCs as well as other cell types and imaging them using a standard fluorescent microscope at the single cell level. Furthermore, it can be integrated with other miniaturized optical modules to construct a portable platform for counting a wide variety of cells and therefore it can be an excellent tool for monitoring human diseases at the point-of-care.

Effect of shiftwork on systemic markers of inflammation

Shiftwork is associated with an increased risk of cardiovascular diseases, but the possible role of inflammation in this relationship is not well known. We tested the hypothesis that shiftwork would be associated with higher levels of C-reactive protein (CRP) and increased leukocyte count. We analyzed the cross-sectional associations between work arrangements and low-grade inflammation in 1877 airline-company employees separately for men (n = 1037) and women (n = 840). The participants were classified into five categories according to their work schedule: day workers who have not worked in shifts (referent group), former shiftworkers, 2-shift workers, 3-shift workers, and in-flight workers. In models adjusted for age and recent infectious diseases, CRP levels were higher among male 3-shift workers (p = .002) and marginally higher in male 2-shift workers (p = .076). In addition, leukocyte count was higher in 2-shift (p = .005) and 3-shift (p = .021) working men. In women, CRP level was higher in 2-shift workers (p = .028), whereas leukocyte count was lower in flight workers (p = .005). Any separate adjustment additionally for smoking, education, alcohol consumption, physical activity, and obesity did not substantially affect the results of 2- and 3-shift work. In the fully adjusted model, only the association between 3-shift work and CRP in men (p = .021) and 2-shift work and leukocyte count in men (p = .020) and leukocyte count in 3-shift-working women (p = .044) were significant. Our results suggest that 2- and 3-shift work is associated with increased systemic inflammation and the relationship is relatively independent of the considered risk factors of cardiovascular disease.

Night work and inflammatory markers

BACKGROUND

Various adverse health effects associated with shift work have been documented in the medical literature. These include increased risk of cardiovascular disorders, cerebrovascular disorders, and mortality. Sleep deprivation has been shown to be associated with an elevation in inflammatory makers such as interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). It is hypothesized that the increased risk of many disorders associated with shift work may be due to inflammatory processes resulting from sleep deprivation. The purpose of this study was to investigate the relationship between night work and inflammatory markers.

MATERIALS AND METHODS

Fifty workers were selected according to the specified inclusion and exclusion criteria and randomly assigned to one of two groups in a cross over study. The 25 workers in group 1 were scheduled to work the following consecutive shifts: three day shifts, one day off, and three night shifts. Group 2 were scheduled to work the following consecutive shifts: three night shifts, one day off, and three day shifts. Blood samples were obtained between 7:A.M. and 8:A.M. after the periods of day work and night work and tested for inflammatory markers.

STATISTICAL ANALYSES

SPSS 11.5 and S-data were used to analyze data using the Student's t-test and paired t-test.

RESULTS

There was a statistically significant increase in IL-6, CRP, white blood cells, neutrophils, lymphocytes, and platelets following night work compared with day work. TNF-α was increased but it was not statistically significant, and also the change in monocyte counts was not significant.

CONCLUSION

This study demonstrated an increase in inflammatory markers following night work, as reported in several pervious studies on sleep deprivation. No significant changes in monocyte count can be justified by the results of a study which showed that the elevation in blood levels of inflammatory markers is due to increase in gene expression, not in monocyte counts.

Immune, inflammatory and cardiovascular consequences of sleep restriction and recovery

In addition to its effects on cognitive function, compelling evidence links sleep loss to alterations in the neuroendocrine, immune and inflammatory systems with potential negative public-health ramifications. The evidence to suggest that shorter sleep is associated with detrimental health outcomes comes from both epidemiological and experimental sleep deprivation studies. This review will focus on the post-sleep deprivation and recovery changes in immune and inflammatory functions in well-controlled sleep restriction laboratory studies. The data obtained indicate non-specific activation of leukocyte populations and a state of low-level systemic inflammation after sleep loss. Furthermore, one night of recovery sleep does not allow full recovery of a number of these systemic immune and inflammatory markers. We will speculate on the mechanism(s) that link(s) sleep loss to these responses and to the progression of cardiovascular disease. The immune and inflammatory responses to chronic sleep restriction suggest that chronic exposure to reduced sleep (<6 h/day) and insufficient time for recovery sleep could have gradual deleterious effects, over years, on cardiovascular pathogenesis with a heightened risk in women and in night and shift workers. Finally, we will examine countermeasures, e.g., napping or sleep extension, which could improve the recovery processes, in terms of alertness and immune and inflammatory parameters, after sleep restriction.

Individual differences in tolerance to shift work--a systematic review

Shift work tolerance is a term describing the ability to adapt to shift work without adverse consequences. In this paper we systematically review literature published investigating the relation between individual differences such as age, gender, personality, morningness/eveningness as well as biological variables and different measures of shift work tolerance from 1998 till 2009. A total of 60 articles were included in this review, of which ten studies were classified as longitudinal, while the rest were classified as cross-sectional. Overall, the studies indicate that young age, male gender, low scores on morningness, high scores on flexibility and low scores on languidity, low scores on neuroticism, high scores on extraversion and internal locus of control and some genetic dispositions are related to higher shift work tolerance. More longitudinal studies, especially concerning personality, are needed to make conclusions about the predictive power of individual differences for shift work tolerance.

Obstructive sleep apnea and immunity: relationship of lymphocyte count and apnea hypopnea index

OBJECTIVES

The impact of chronic poor quality sleep on immunity as seen in obstructive sleep apnea (OSA) has not been evaluated. We aim to explore the relationship between lymphocytes, neutrophil, and total leukocyte counts with severity stratified apnea hypopnea index (AHI) in patients with OSA.

METHODS

A retrospective review of 119 patients' medical records diagnosed with OSA from October 2005 to July 2006 was performed. Data collected included demographics, comorbidities, total leukocyte, neutrophil, and lymphocyte count, body mass index (BMI), AHI, and Epworth sleepiness scores (ESS). Three AHI strata were constructed: mild (5-14), moderate (15-29), and severe (>30). Data were fitted in a linear regression model on which lymphocyte counts were the dependent variable against age, BMI, and AHI. An interaction product was also explored (age*BMI). All tests were two-sided; a P < 0.05 was considered statistically significant. We used Statview Version 5.01 (SAS Institute, Inc., Cary, NC) for the analysis.

RESULTS

Our study showed a linear association among AHI and BMI (P = 0.0017), but did not show association between lymphocyte count with either BMI (P = 0.33) or AHI (P = 0.90). A negative association between lymphocytes and age (P = 0.02) that persisted after adjustments for BMI and AHI was found. An interaction product (age*AHI) was not associated with lymphocyte count (P = 0.87). No correlation was found between peripheral blood count (P = 0.29) or neutrophil counts (P = 0.38) and AHI.

CONCLUSION

We found OSA-induced sleep interruption not associated with lymphocyte, neutrophil, or peripheral blood cell count alterations. This information is useful for researchers evaluating the influence of sleep disruption on immunity.

Having more healthy practice was associated with low white blood cell counts in middle-aged Japanese male and female workers

White blood cell (WBC) count is well known to be an independent risk marker for cardiovascular disease. The aim of this study is to examine the relationships of WBC counts to seven health practices including obesity, eating habits, smoking, alcohol intake, sleeping, physical activity, and perceived mental stress, and then clustering the relevant healthy practices. The subjects were 1,492 male and 316 female Japanese workers aged 40 yr and over in 2002. Each of seven health practices from a self-administered questionnaire was categorized as a 'healthy' or 'unhealthy' practice, and WBC counts from fasting blood samples were determined by automated particle counters. The means of age and WBC counts were 49.5 yr and 5,375 cells/microl in men, and 48.6 yr and 4,890 cells/microl in women, respectively. After multivariate adjustments for all health practices and age, the estimated WBC counts were significantly lower in normal weight subjects and never or former smokers (p<0.01). Age-adjusted WBC counts decreased significantly by 204.9+/-23.7 cells/microl (means+/-SE) and 117.6+/-53.2 cells/microl for each increase in one healthy practice (p<0.05), respectively, suggesting that cultivating healthier practices would lead to lower WBC counts. This study recommends modifying unhealthy practice one by one and maintaining healthy practices as an effective strategy for the prevention of atherosclerotic diseases, in addition, to quit smoking or abstain from heavy smoking especially in men is important to prevent the low-grade inflammation.