The association between chronotype and sleep quality among female home care workers performing shift work.

There is a scarcity of evidence on the association between shift work, sleeping parameters, heart rate variability (HRV), and chronotype, i.e., morningness and eveningness. The aims of this study were to 1) compare participants with different chronotypes (morning (M), evening (E), or neither (N)) in terms of their total sleep time, sleep efficiency, and HRV parameters, taking their age into account, and 2) examine whether self-reported work-related stress, the length of the working career and years performing shift work affect this association. The participants of the study were home care workers working in two shifts in one municipality in Eastern Finland (N = 395). Of these, 52 females (mean age 42.78 y, SD 12.92 y) completed the study questionnaire and participated in physiological measurements. Several sleep-related parameters were assessed (total sleep time, sleep efficiency, number of awakenings, and length of awakening) and indices of autonomic nervous system based on HRV were calculated. The participants worked in two shifts: a morning shift (7:00-15:00 h) and an evening shift (14:00-21:30 h). All these parameters were assessed during the night before the first work shift (N1), the night before the second work shift (N2), the night before the final work shift (N3), and the night before the first day off work (N4). According to the results, 21.2% of the participants were M-types, 17.3% were E-types, and 61.5% were N-types. On average, the participants had been in working life for 18.8 years and performing shift work for 13.7 years. On night N3, E-types had a significantly shorter total sleep time and spent less time in bed compared to M- and N-types. The total sleep time of M-type and N-type participants was on average 66 minutes and 82 minutes longer, respectively, when compared to E-types on night N3. There were no statistically significant differences in actigraphy-based sleep quality parameters between M-, N-, and E-types on nights N1, N2, and N4. Our results together indicate that M- and N-type individuals may have better sleep quality than E-types, which was also reflected in HRV parameters. Further research with longitudinal study design and workplace interventions is needed to determine how the chronotype can be optimally and individually utilized to improve the health and well-being of morning-type and evening-type people. This is particularly important for both younger and older workers entering the workforce to support healthier and longer working lives.

Plant Stanol Esters Reduce LDL (Low-Density Lipoprotein) Aggregation by Altering LDL Surface Lipids: The BLOOD FLOW Randomized Intervention Study.

OBJECTIVE: Plant stanol ester supplementation (2-3 g plant stanols/d) reduces plasma LDL (low-density lipoprotein) cholesterol concentration by 9% to 12% and is, therefore, recommended as part of prevention and treatment of atherosclerotic cardiovascular disease. In addition to plasma LDL-cholesterol concentration, also qualitative properties of LDL particles can influence atherogenesis. However, the effect of plant stanol ester consumption on the proatherogenic properties of LDL has not been studied. Approach and Results: Study subjects (n=90) were randomized to consume either a plant stanol ester-enriched spread (3.0 g plant stanols/d) or the same spread without added plant stanol esters for 6 months. Blood samples were taken at baseline and after the intervention. The aggregation susceptibility of LDL particles was analyzed by inducing aggregation of isolated LDL and following aggregate formation. LDL lipidome was determined by mass spectrometry. Binding of serum lipoproteins to proteoglycans was measured using a microtiter well-based assay. LDL aggregation susceptibility was decreased in the plant stanol ester group, and the median aggregate size after incubation for 2 hours decreased from 1490 to 620 nm, P=0.001. Plant stanol ester-induced decrease in LDL aggregation was more extensive in participants having body mass index<25 kg/m2. Decreased LDL aggregation susceptibility was associated with decreased proportion of LDL-sphingomyelins and increased proportion of LDL-triacylglycerols. LDL binding to proteoglycans was decreased in the plant stanol ester group, the decrease depending on decreased serum LDL-cholesterol concentration. CONCLUSIONS: Consumption of plant stanol esters decreases the aggregation susceptibility of LDL particles by modifying LDL lipidome. The resulting improvement of LDL quality may be beneficial for cardiovascular health. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01315964.

Deep learning for prediction of cardiac indices from photoplethysmographic waveform: A virtual database approach.

Deep learning methods combined with large datasets have recently shown significant progress in solving several medical tasks. However, collecting and annotating large datasets can be a very cumbersome and expensive task. We tackle these problems with a virtual database approach where training data is generated using computer simulations of related phenomena. Specifically, we concentrate on the following problem: can cardiovascular indices such as aortic elasticity, diastolic and systolic blood pressures, and blood flow from heart be predicted continuously using wearable photoplethysmographic sensors? We simulate the blood flow using a haemodynamic model consisting of the entire human circulation. Repeated evaluation of the simulator allows us to create a database of "virtual subjects" with size that is only limited by available computational resources. Using this database, we train neural networks to predict the cardiac indices from photoplethysmographic signal waveform. We consider two approaches: neural networks based on predefined input features and deep convolutional neural networks taking waveform directly as the input. The performance of the methods is demonstrated using numerical examples, thus carrying out a preliminary assessment of the approaches. The results show improvements in accuracy compared with the previous methods. The improvements are especially significant with indices related to aortic elasticity and maximum blood flow. The proposed approach would provide new means to measure cardiovascular health continuously, for example, with a simple wrist device.

Clinical Characteristics of Disability in Patients with Indoor Air-Related Environmental Intolerance.

BACKGROUND: Chronic nonspecific symptoms attributed to indoor nonindustrial work environments are common and may cause disability, but the medical nature of this disability is unclear. The aim was to medically characterize the disability manifested by chronic, recurrent symptoms and restrictions to work participation attributed to low-level indoor pollutants at workplace and whether the condition shares features with idiopathic environmental intolerance. METHODS: We investigated 12 patients with indoor air-related work disability. The examinations included somatic, psychological, and psychiatric evaluations as well as investigations of the autonomic nervous system, cortisol measurements, lung function, and allergy tests. We evaluated well-being, health, disability, insomnia, pain, anxiety, depression, and burnout via questionnaires. RESULTS: The mean symptom history was 10.5 years; for disabling symptoms, 2.7 years. Eleven patients reported reactions triggered mainly by indoor molds, one by fragrances only. Ten reported sensitivity to odorous chemicals, and three, electric devices. Nearly all had co-occurrent somatic and psychiatric diagnoses and signs of pain, insomnia, burnout, and/or elevated sympathetic responses. Avoiding certain environments had led to restrictions in several life areas. On self-assessment scales, disability showed higher severity and anxiety showed lower severity than in physician assessments. CONCLUSION: No medical cause was found to explain the disability. Findings support that the condition is a form of idiopathic environmental intolerance and belongs to functional somatic syndromes. Instead of endless avoidance, rehabilitation approaches of functional somatic syndromes are applicable.

Pulse transit time estimation of aortic pulse wave velocity and blood pressure using machine learning and simulated training data.

Recent developments in cardiovascular modelling allow us to simulate blood flow in an entire human body. Such model can also be used to create databases of virtual subjects, with sizes limited only by computational resources. In this work, we study if it is possible to estimate cardiovascular health indices using machine learning approaches. In particular, we carry out theoretical assessment of estimating aortic pulse wave velocity, diastolic and systolic blood pressure and stroke volume using pulse transit/arrival timings derived from photopletyshmography signals. For predictions, we train Gaussian process regression using a database of virtual subjects generated with a cardiovascular simulator. Simulated results provides theoretical assessment of accuracy for predictions of the health indices. For instance, aortic pulse wave velocity can be estimated with a high accuracy (r > 0.9) when photopletyshmography is measured from left carotid artery using a combination of foot-to-foot pulse transmit time and peak location derived for the predictions. Similar accuracy can be reached for diastolic blood pressure, but predictions of systolic blood pressure are less accurate (r > 0.75) and the stroke volume predictions are mostly contributed by heart rate.

Plasma irisin is increased following 12 weeks of Nordic walking and associates with glucose homoeostasis in overweight/obese men with impaired glucose regulation.

Irisin is a myokine that is thought to be secreted in response to exercise that may help to prevent obesity and maintain normal glucose metabolism. In this study we investigated the associations between irisin and glucose homeostasis in middle-aged, overweight and obese men (n = 144) with impaired glucose regulation, and the impact of exercise training on these relationships. The participants underwent 12 weeks of resistance or aerobic (Nordic walking) exercise training three times per week, 60 minutes per session. Venous blood (n = 105) and skeletal muscle samples (n = 45) were obtained at baseline and post-intervention. Compared to controls, Nordic walking, but not resistance training, increased irisin levels in plasma (9.6 ± 4.2%, P = 0.014; 8.7 ± 4.9%, P = 0.087; respectively) compared to controls. When considering all subjects, baseline irisin correlated positively with atherogenic index of plasma (r = 0.244, P = 0.013) and 2-hour insulin levels (r = 0.214, P = 0.028), and negatively with age (r = -0.262, P = 0.007), adiponectin (r = -0.240, P = 0.014) and McAuley index (r = -0.259, P = 0.008). Training-induced FNDC5 mRNA changes were negatively correlated with HbA1c (r = -0.527, P = 0.030) in the resistance training group and with chemerin in the Nordic walking group (r = -0.615, P = 0.033). In conclusion, 12-weeks of Nordic walking was more effective than resistance training in elevating plasma irisin, in middle-aged men with impaired glucose tolerance. Thus, the change in irisin in response to exercise training varied by the type of exercise but showed limited association with improvements in glucose homeostasis.

Estimation of Beat-to-Beat Interval and Systolic Time Intervals Using Phono- and Seismocardiograms.

Systolic time intervals Pre-Ejection Period (PEP) and Left Ventricular Ejection Time (LVET) are widely used indicators of cardiac functions. While accurate assessment of them requires costly equipment such as echocardiography devices, a satisfactory estimation can be done by analyzing signals from simple accelerometer and microphone attached to human chest. This paper reports a study where heart rate and the systolic intervals were derived from phonocardiogram (PCG) and seismocardiogram (SCG) simultaneously. Both sensors, the microphone for PCG and the accelerometer for SCG were attached on the chest wall, close to sternum (PCG) and apex of the heart (SCG). The signals were acquired from 10 participants in a 33-minute laboratory protocol with synchronized ECG measurements. Both signals went through an identical processing path: band pass filtering, envelope extraction with Hilbert transformation and peak detection from the envelope signal. In heart rate estimation, PCG and SCG reached 84% and 93% accuracy, respectively. The systolic interval accuracy estimation was based on deviation analysis as the absolute reference values for PEP and LVET were not available. In PEP estimation, the average standard deviations during the rest periods of the protocol were 4 ms for PCG and 8 ms for SCG. In LVET estimation, the deviations were nearly 10 fold compared to PEP. However, the results show that both methods can be used for accurate heart rate estimation and with careful mechanical attachment also PEP can be accurately derived from both. Due to sharper envelope signal waveform, PEP estimation was more accurate with PCG than with SCG.

Variations of Heart Rate, Pulse Arrival Time and Blood Pressure in a Versatile Laboratory Protocol.

Many studies dealing with blood pressure modeling are evaluated based on a single type of provocation. This paper investigates widely used provocations such as controlled breathing, mental arithmetic and Stroop tests, Valsalva maneuver, cold pressor and muscle tension and combines them in a versatile laboratory protocol. The protocol was tested in an experiment where pulse arrival time (PAT) and heart rate (HR) were measured with chest ECG and finger PPG sensors and blood pressure (BP) with continuous fingercuff monitor. The experiment results show that mental tasks provoked HR, BP and PAT very little while cold pressor and muscle tension had strong impact in all parameters. Valsalva maneuver had strongest impact in HR and PAT but the effect was transient like. We also predicted systolic BP based on the PAT values. We selected nine points in the protocol to calculate linear prediction model for each subject and then fitted data points to the models. If only the calibration points are taken into account, the correlation between the predicted and measured systolic BP was 0.91. When all the data points are fed into model, correlation was 0.75.

A chair based ballistocardiogram time interval measurement with cardiovascular provocations.

The objective of this study was to measure ballistocardiogram (BCG) based time intervals and compare them with systolic blood pressure values. Electrocardiogram (ECG) and BCG signals of six subjects sitting in a chair were measured with a ferroelectret film sensor. Time intervals between ECG R peak and BCG I and J waves were calculated to obtain RJ, RI and IJ intervals. The time intervals were modified with two cardiovascular provocations, controlled breathing and Valsalva maneuver. The controlled breathing changed all the time intervals (RJ, RI and IJ) whereas the Valsalva maneuver mainly caused variations in the RJ and RI intervals. The calculated time intervals were compared with reference arterial blood pressure values. Correlation coefficients of r = -0.61 and r = -0.78 were found between the RJ and RI time intervals and systolic blood pressure during Valsalva maneuver, respectively.

Comparison of photoplethysmogram measured from wrist and finger and the effect of measurement location on pulse arrival time.

OBJECTIVE: The aim of this paper was to compare photoplethysmogram (PPG) signals measured from the wrist and finger and to evaluate if wrist PPG signal could be used to calculate pulse arrival time (PAT), the time delay between electrocardiogram (ECG) R peak and a feature (e.g. peak, foot, first derivative peak) in the PPG signal. Further, the correlation between pulse wave velocity (rePWV, defined as PWV from ECG R peak to extremity) and systolic blood pressure was studied. APPROACH: Thirty subjects were measured at rest by a trained research nurse. For reference measurement, chest ECG and finger PPG were measured using commercial sensors. Wrist PPG and arm ECG were measured with a custom-made setup, where the PPG sensor was located at the back surface of the forearm. MAIN RESULTS: Reference finger and wrist PPG signals were found to differ in shape and also in amplitude. The PPG foot or first derivative peak detection methods seemed to be the most suitable methods for wrist PAT calculation. The Pearson correlation coefficient between blood pressure and rePWV was found to be 0.44 for the reference finger measurement and 0.37 for the wrist measurement. SIGNIFICANCE: Wrist PPG signal is widely used in optical heart rate monitors. Based on the results obtained in this study, wrist PPG signal may be used also for PAT calculation. The use of PAT for blood pressure estimation still has challenges, but PAT as such could be used as an interesting indicator of vascular health.

Acute Effect of Alcohol Intake on Cardiovascular Autonomic Regulation During the First Hours of Sleep in a Large Real-World Sample of Finnish Employees: Observational Study.

BACKGROUND: Sleep is fundamental for good health, and poor sleep has been associated with negative health outcomes. Alcohol consumption is a universal health behavior associated with poor sleep. In controlled laboratory studies, alcohol intake has been shown to alter physiology and disturb sleep homeostasis and architecture. The association between acute alcohol intake and physiological changes has not yet been studied in noncontrolled real-world settings. OBJECTIVE: The aim of this study was to assess the effects of alcohol intake on the autonomic nervous system (ANS) during sleep in a large noncontrolled sample of Finnish employees. METHODS: From a larger cohort, this study included 4098 subjects (55.81%, 2287/4098 females; mean age 45.1 years) who had continuous beat-to-beat R-R interval recordings of good quality for at least 1 day with and for at least 1 day without alcohol intake. The participants underwent continuous beat-to-beat R-R interval recording during their normal everyday life and self-reported their alcohol intake as doses for each day. Heart rate (HR), HR variability (HRV), and HRV-derived indices of physiological state from the first 3 hours of sleep were used as outcomes. Within-subject analyses were conducted in a repeated measures manner by studying the differences in the outcomes between each participant's days with and without alcohol intake. For repeated measures two-way analysis of variance, the participants were divided into three groups: low (≤0.25 g/kg), moderate (>0.25-0.75 g/kg), and high (>0.75 g/kg) intake of pure alcohol. Moreover, linear models studied the differences in outcomes with respect to the amount of alcohol intake and the participant's background parameters (age; gender; body mass index, BMI; physical activity, PA; and baseline sleep HR). RESULTS: Alcohol intake was dose-dependently associated with increased sympathetic regulation, decreased parasympathetic regulation, and insufficient recovery. In addition to moderate and high alcohol doses, the intraindividual effects of alcohol intake on the ANS regulation were observed also with low alcohol intake (all P<.001). For example, HRV-derived physiological recovery state decreased on average by 9.3, 24.0, and 39.2 percentage units with low, moderate, and high alcohol intake, respectively. The effects of alcohol in suppressing recovery were similar for both genders and for physically active and sedentary subjects but stronger among young than older subjects and for participants with lower baseline sleep HR than with higher baseline sleep HR. CONCLUSIONS: Alcohol intake disturbs cardiovascular relaxation during sleep in a dose-dependent manner in both genders. Regular PA or young age do not protect from these effects of alcohol. In health promotion, wearable HR monitoring and HRV-based analysis of recovery might be used to demonstrate the effects of alcohol on sleep on an individual level.

Physiological and autonomic stress responses after prolonged sleep restriction and subsequent recovery sleep in healthy young men.

PURPOSE: Sleep restriction is increasingly common and associated with the development of health problems. We investigated how the neuroendocrine stress systems respond to prolonged sleep restriction and subsequent recovery sleep in healthy young men. METHODS: After two baseline (BL) nights of 8 h time in bed (TIB), TIB was restricted to 4 h per night for five nights (sleep restriction, SR, n = 15), followed by three recovery nights (REC) of 8 h TIB, representing a busy workweek and a recovery weekend. The control group (n = 8) had 8 h TIB throughout the experiment. A variety of autonomic cardiovascular parameters, together with salivary neuropeptide Y (NPY) and cortisol levels, were assessed. RESULTS: In the control group, none of the parameters changed. In the experimental group, heart rate increased from 60 ± 1.8 beats per minute (bpm) at BL, to 63 ± 1.1 bpm after SR and further to 65 ± 1.8 bpm after REC. In addition, whole day low-frequency to-high frequency (LF/HF) power ratio of heart rate variability increased from 4.6 ± 0.4 at BL to 6.0 ± 0.6 after SR. Other parameters, including salivary NPY and cortisol levels, remained unaffected. CONCLUSIONS: Increased heart rate and LF/HF power ratio are early signs of an increased sympathetic activity after prolonged sleep restriction. To reliably interpret the clinical significance of these early signs of physiological stress, a follow-up study would be needed to evaluate if the stress responses escalate and lead to more unfavourable reactions, such as elevated blood pressure and a subsequent elevated risk for cardiovascular health problems.

Pulse arrival time (PAT) measurement based on arm ECG and finger PPG signals - comparison of PPG feature detection methods for PAT calculation.

In this study, pulse arrival time (PAT) was measured using a simple measurement setup consisting of arm electrocardiogram (ECG) and finger photoplethysmogram (PPG). Four methods to calculate PAT from the measured signals were evaluated. PAT was calculated as the time delay between ECG R peak and one of the following points in the PPG waveform: peak (maximum value of PPG waveform), foot (minimum value of PPG waveform), dpeak (maximum value of the first derivative of PPG waveform) and ddpeak (maximum value of the second derivative of PPG waveform). In addition to PAT calculation, pulse period (PP) intervals based on the detected features were determined and compared to RR intervals derived from ECG signal. Based on the results obtained here, the most promising method to be used in PAT or PP calculation seems to be the dpeak detection method.

Pulse arrival time measurement with coffee provocation.

This study investigated the effect of coffee intake in pulse arrival time (PAT) and pulse wave velocity (PWV) measured with electrocardiogram (ECG) from arms and photoplethysmogram (PPG) from fingertip. In addition, correlation of PWV with blood pressure (BP) is analyzed. 30 healthy participants were recruited to two measurement sessions, one arranged before and another one after the coffee intake. During each session, ECG and PPG were measured continuously for six minutes and PAT values calculated from ECG R-peak to the maximum of the first derivative of the PPG pulse. In addition, blood pressure was measured twice during each session with cuff based method. Coffee intake had statistically significant influence on both systolic and diastolic blood pressure, but not on PAT or PWV. Correlation between systolic blood pressure and PWV was 0.44. Individual calibration, additional derivatives of ECG and PPG such as heart rate, pulse pressure, or waveform characteristics could improve the correlation.

Salivary cortisol and alpha-amylase: Is there consistency between psychosocial stress test and burdensome work shifts?

This study examined the consistency of salivary cortisol and alpha-amylase (sAA) total daily secretion between laboratory and field circumstances. The 95 participants were shift working female health care professionals with high (n = 53) or low (n = 42) psychosocial stress (job strain) measured by the Job Content Questionnaire (JCQ). The Trier Social Stress Test including a 5-min free speech and a mental arithmetic task was conducted with four, and field measurements with three daily saliva samples of cortisol and sAA during circadian rhythm and inter-shift recovery controlled morning shift, night shift, and a day off. The associations of salivary cortisol and sAA area under the curve with respect to ground (AUCg) and area under the curve with respect to increase (AUCi) between laboratory and field were tested using OLS (Ordinary Least Squares) regression. The sAA AUCg output in the laboratory was correlated with the output during all field measurement days and similarly among high and low job strain groups (p < 0.001). SAA AUCi and salivary cortisol AUCg and AUCi were not correlated between laboratory and field measurement, neither in the whole sample nor among the low or high job strain group. In conclusion, a laboratory measure of sAA AUCg output is promising in predicting stress-related output during burdensome work shifts and leisure time, whereas sAA AUCi or salivary cortisol seem not to have this potential.

Recovery of rescuers from a 24-h shift and its association with aerobic fitness.

OBJECTIVES: Rescuers work in 24-h shifts and the demanding nature of the occupation requires adequate recovery between work shifts. The purpose of this study has been to find out what kind of changes in autonomic control may be seen during work shift and its recovery period in the case of rescuers. An additional interest has been to see if aerobic fitness is associated with recovery from work shifts. MATERIAL AND METHODS: Fourteen male rescuers (aged 34±9 years old) volunteered to participate in the study. Heart rate variability (HRV) was recorded for 96 h to study stress and recovery, from the beginning of a 24-h work shift to the beginning of the next shift. Aerobic fitness assessment included maximal oxygen uptake (VO2max) estimation with a submaximal bicycle ergometer test. Salivary cortisol samples were collected 0 min, 15 min, and 30 min after awakening on the 3 resting days. RESULTS: Some HRV parameters showed enhanced autonomic control after the work shift. Stress percentage decreased from the working day to the 2nd rest day (p < 0.05). However, maximal oxygen uptake was not associated with enhanced parasympathetic cardiac control (p > 0.05). Cortisol awakening response was attenuated right after the work shift. CONCLUSIONS: The HRV findings show that recovery after a long work shift takes several days. Thus, rescuers should pay attention to sufficient recovery before the next work shift, and an integrated model of perceived and physiological measurements could be beneficial to assess cardiovascular strain among rescuers with long work shifts. Int J Occup Med Environ Health 2017;30(3):433-444.

Physiological Load and Psychological Stress During a 24-hour Work Shift Among Finnish Firefighters.

OBJECTIVE: The aim of this study was to describe physiological load and psychological stress of Finnish firefighters during a 24-hour work shift. METHODS: R-R intervals were recorded during 24-hour work shifts. Short-time Fourier transform was used to analyze heart rate variability during shifts. RESULTS: HRmean, HRpeak, and square root of the mean of the sum of the squares of the differences between adjacent R-to-R peak intervals of the 24-hour shift was 73 ±â€Š7 bpm (38 ±â€Š4% of HRmax), 156 ±â€Š16 bpm (82 ±â€Š8% of HRmax), and 42 ±â€Š14 ms. Mean VO2 was 11 ±â€Š2 (% of VO2max) and VO2peak 72 ±â€Š11 (% of VO2max). CONCLUSIONS: Physiological load and psychological stress were temporarily high, even in young, fit firefighters. As the relative work load may increase and recovery processes slow down among aging employees, fatigue may occur unless work arrangements are well-designed.

Neuromuscular exercise and back counselling for female nursing personnel with recurrent non-specific low back pain: study protocol of a randomised controlled trial (NURSE-RCT).

INTRODUCTION: Nursing personnel have high risk for incidence of low back pain (LBP) followed by development of chronic pain and disability. Multiple risk factors such as patient handling, night shift work and lack of supporting work culture have been identified. In subacute LBP, high-fear avoidance is prognostic for more pain, disability and not returning to work. Lack of leisure-time physical activity predicts long-term sickness absence. The purpose of this study is to compare effectiveness of 6-month neuromuscular exercise and counselling in treating back pain in female nursing personnel with recurrent non-specific LBP pain compared with either (exercise or counselling) alone and a non-treatment control group. METHODS AND ANALYSIS: The design is of a double-blinded four-arm randomised controlled trial with cost-effectiveness evaluation at 12 and 24 months. The study is conducted in 3 consecutive substudies. The main eligibility criteria are experience of LBP during the past 4 weeks with intensity of at least 2 (Numeric Rating Scale 0-10) and engagement in patient handling. Sample size was estimated for the primary outcome of pain intensity (visual analogue scale). Study measurements are outlined according to the model of International Classification of Functioning, Disability and Health, which incorporates the biopsychosocial processes assessed. ETHICS AND DISSEMINATION: This study is carried out conforming to the guidelines of good scientific practice and provisions of the declaration of Helsinki. Increasing physical and mental capacity with interventions taking place immediately after working hours near the worksite may reduce development of chronic LBP and work disability in female nursing personnel with recurrent non-specific LBP. TRIAL REGISTRATION NUMBER: NCT04165698.

Physical activity, body mass index and heart rate variability-based stress and recovery in 16 275 Finnish employees: a cross-sectional study.

BACKGROUND: Physical inactivity, overweight, and work-related stress are major concerns today. Psychological stress causes physiological responses such as reduced heart rate variability (HRV), owing to attenuated parasympathetic and/or increased sympathetic activity in cardiac autonomic control. This study's purpose was to investigate the relationships between physical activity (PA), body mass index (BMI), and HRV-based stress and recovery on workdays, among Finnish employees. METHODS: The participants in this cross-sectional study were 16 275 individuals (6863 men and 9412 women; age 18-65 years; BMI 18.5-40.0 kg/m(2)). Assessments of stress, recovery and PA were based on HRV data from beat-to-beat R-R interval recording (mainly over 3 days). The validated HRV-derived variables took into account the dynamics and individuality of HRV. Stress percentage (the proportion of stress reactions, workday and working hours), and stress balance (ratio between recovery and stress reactions, sleep) describe the amount of physiological stress and recovery, respectively. Variables describing the intensity (i.e. magnitude of recognized reactions) of physiological stress and recovery were stress index (workday) and recovery index (sleep), respectively. Moderate to vigorous PA was measured and participants divided into the following groups, based on calculated weekly PA: inactive (0 min), low (0 < 150 min), medium (150-300 min), and high (>300 min). BMI was calculated from self-reported weight and height. Linear models were employed in the main analyses. RESULTS: High PA was associated with lower stress percentages (during workdays and working hours) and stress balance. Higher BMI was associated with higher stress index, and lower stress balance and recovery index. These results were similar for men and women (P < 0.001 for all). CONCLUSION: Independent of age and sex, high PA was associated with a lower amount of stress on workdays. Additionally, lower BMI was associated with better recovery during sleep, expressed by a greater amount and magnitude of recovery reactions, which suggests that PA in the long term resulting in improved fitness has a positive effect on recovery, even though high PA may disturb recovery during the following night. Obviously, several factors outside of the study could also affect HRV-based stress.

High indoor CO2 concentrations in an office environment increases the transcutaneous CO2 level and sleepiness during cognitive work.

The purpose of this study is to perform a multiparametric analysis on the environmental factors, the physiological stress reactions in the body, the measured alertness, and the subjective symptoms during simulated office work. Volunteer male subjects were monitored during three 4-hr work meetings in an office room, both in a ventilated and a non-ventilated environment. The environmental parameters measured included CO(2), temperature, and relative humidity. The physiological test battery consisted of measuring autonomic nervous system functions, salivary stress hormones, blood's CO(2)- content and oxygen saturation, skin temperatures, thermal sensations, vigilance, and sleepiness. The study shows that we can see physiological changes caused by high CO(2) concentration. The findings support the view that low or moderate level increases in concentration of CO(2) in indoor air might cause elevation in the blood's transcutaneously assessed CO(2). The observed findings are higher CO(2) concentrations in tissues, changes in heart rate variation, and an increase of peripheral blood circulation during exposure to elevated CO(2) concentration. The subjective parameters and symptoms support the physiological findings. This study shows that a high concentration of CO(2) in indoor air seem to be one parameter causing physiological effects, which can decrease the facility user's functional ability. The correct amount of ventilation with relation to the number of people using the facility, functional air distribution, and regular breaks can counteract the decrease in functional ability. The findings of the study suggest that merely increasing ventilation is not necessarily a rational solution from a technical-economical viewpoint. Instead or in addition, more comprehensive, anthropocentric planning of space is needed as well as instructions and new kinds of reference values for the design and realization of office environments.