Fred Haugen

Objectives: Pain is a hallmark of musculoskeletal conditions. Some studies suggest that pain is exacerbated by working in cold environments, potentially due to poorly understood mechanisms within the somatosensory system. The aim of this study was to assess whether ambient cold exposure influences the efficiency of endogenous pain inhibition and the potential role of subjective thermal comfort. Methods: In a crossover study with 1 week interval and in randomized order, 20 healthy men were exposed to cold (COLD; 10 °C) and thermoneutral (TN; 22 °C) conditions in a controlled environment room (CER) for 2 h. Conditioned pain modulation (CPM), defined as the difference in mean rated pain of a test stimuli (TS) with and without a conditioning stimulus (CS), was calculated before and after CER. Test stimuli (TS) was a 30 s tonic noxious heat stimulation to the dominant volar forearm, and conditioning stimuli (CS) was immersion of the contralateral hand in water holding 4 °C. Subjective TS pain was rated on a 0–10 cm computerized Visual Analogue Scale (VAS). Thermal comfort, encompassing subjective thermal perception, evaluation, and preference, was assessed using standardized subjective judgment scales. Results: The CPM-effect was significantly reduced by COLD exposure, but not by TN exposure. As expected, participants’ ratings of thermal comfort changed across exposure conditions; however, this had no significant influence on the CPM-effect. Conclusions: Exposure to cold ambient conditions impaired endogenous pain-inhibitory pathways, an outcome not observed under thermoneutral conditions. Furthermore, the results suggest that thermal comfort does not influence endogenous pain-inhibitory pathways. Further research is required to identify moderators affecting pain processing in cold working environments. Regional Ethics Committee, Norway (REK sør-øst C; application # 2017/1859).

Objective To systematically review the evidence on the association between non-standard working time arrangements (such as night work or shift work) and the occurrence of safety incidents. Design Systematic review conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and using a structured narrative approach and the Synthesis Without Meta-analysis framework to evaluate and summarise findings. Data sources MEDLINE, Embase, PsycINFO, Web of Science and ProQuest Health and Safety Science Abstracts were searched through February 2024. Eligibility criteria for selecting studies We included peer-reviewed English-language studies of paid workers (18–70 years) that examined the association between non-standard working time arrangements and safety incidents (accidents, near-accidents, safety incidents or injuries), excluding cross-sectional designs and studies on unpaid workers, athletes or military personnel. Data extraction and synthesis Two reviewers independently extracted data and assessed risk of bias using standardised forms, extracting study characteristics (author, year, country, sector and population), working time arrangements and exposure assessment, outcomes and their assessment, and reported risk estimates. We conducted a narrative synthesis, classifying studies into three exposure contrasts (shift worker versus non-shift worker, time-of-day and shift intensity), and summarised risk estimates using forest plots without calculating pooled effects. Results A total of 13 569 records were screened, and 24 studies met the inclusion criteria. The results indicated that shift workers generally had an elevated safety incident risk compared with non-shift workers (risk estimates ranged from 1.11 to 5.33). Most of the included studies found an increased risk of safety incidents during or after night shifts. Accumulated exposure to evening or night shifts increased the risk of safety incidents during the following 7 days. However, bias and heterogeneity across studies in design, populations and outcome measures resulted in an overall low to very low certainty of the evidence. Conclusions Non-standard working time arrangements, including night and evening shifts, appear to increase the risk of occupational safety incidents. Despite the low certainty of evidence, the findings highlight a potential area for preventive measures in work scheduling. Future longitudinal studies using individual data on daily working hours are needed.

Chronotype may play a role in the association between shift work and health risks. An important and widely used questionnaire for measuring chronotype is the Munich Chronotype Questionnaire for Shift workers (MCTQ^Shift); however, it has neither been validated nor is it available in Norwegian or any other Scandinavian language. Therefore, we translated the MCTQ^Shift into Norwegian and assessed its validity against subjective and objective sleep measures. We adhered to established methodological guidelines to translate the questionnaire. The final Norwegian version was administered to 60 workers (85% responders) on a three-shift schedule (21.7% women, median age 28 y) at an industrial plant. Sleep duration and mid-sleep from the MCTQ^Shift were compared with sleep diary and a multisensory sleep tracker (the Oura ring). Construct and criterion validity were evaluated. Sleep duration measured by the MCTQ^Shift was highly correlated (r > 0.6) with sleep duration calculated from both the Oura ring and sleep diaries after morning shifts. On free days, the MCTQ^Shift correlated moderately with the sleep diary but weakly with the Oura ring. Mid-sleep correlations from MCTQ^Shift compared to the Oura ring data were high (r > 0.7) for sleep periods after morning and night shifts, and moderate (r = 0.5) sleep periods between free days following morning shift. Bland-Altman analyses indicated that the MCTQ^Shift overestimated sleep duration and underestimated mid-sleep, with the largest discrepancies on free days after morning shifts. Night shifts showed the most pronounced outliers. The Norwegian MCTQ^Shift shows promising validity for assessing sleep habits in shift workers, particularly on workdays. However, reduced accuracy on free days after morning shifts suggests limitations in capturing sleep patterns across all shift types.

Objective: This study aimed to investigate the impact of occupational thermal exposure on shift workers, specifically whether cold exposure elicits distinct physiological responses and thermoregulatory recovery across different tasks and shift types. Methods: Observational study at two factories processing prawns in Northern Norway in which 32 shift-working seafood handlers with different task responsibilities were followed for a single shift (morning, evening, night). The participants answered questionnaires regarding thermal exposures at work and related symptoms; these were compared to answers from 12 administration workers. Personal thermal loggers measured the range of temperature exposures associated with four different seafood handler work tasks. Pre- and post-shift plasma levels of FGF21, GDF15 and cytokines were analysed using immunoassays. As a proxy for thermoregulatory response across different shift types, hand temperature was measured repeatedly before and after breaks using a thermal imaging camera. Results: Most seafood handlers reported subjective impact from cold exposure. Cold working conditions of ≤ 10 ℃ were measured across all shifts and three different seafood handling tasks. The morning shift—seafood handlers displayed lower plasma FGF21 post-shift vs. pre-shift; the evening and night shifts showed no difference. GDF15 levels remained unchanged regardless of shift types but were positively correlated with age. Night shift was associated with increased plasma IL6 post-shift vs. pre-shift. Thermoregulatory responses showed a positive linear relationship with break duration but did not differ between shifts. Conclusions: The findings suggest that exposure levels are closely linked to specific tasks and shifts, with thermoregulatory responses varying by task type and time of day.

Introduction: Evidence links night shift work to circadian rhythm disruption, causing hormonal and metabolic alterations, as well as increased risk for cardiovascular disease (CVD). This study investigates whether night shift work affects blood glucose variability and dysregulation, potentially driven by circadian misalignment. It also examines whether such disruptions elevate inflammatory markers involved in atherosclerosis and contribute to the exacerbation of CVD risk markers. Methods and analysis: The study includes 60 participants: rotating night shift workers (day, evening, and night shifts) and day workers (controls) at a pharmaceutical plant. We will assess the effects of night shift work on metabolic and cardiovascular health over three phases: an initial 6-week observational period (phase I), baseline registration of CVD risk factors (phase II), and follow-up assessment of CVD risk factors at 2 years (phase III). Phase I registrations include working hours derived from payroll data, sleep metrics by OURA ring (actigraphy, plethysmography and temperature), continuous assessments of blood glucose using continuous glucose monitor, self-reported food diary and measurements of circadian rhythm markers (monocyte mRNA expression). In phases II and III, blood CVD risk factors such as markers of inflammation, lipids, glycosylated haemoglobin, D-dimer, clinical examination of blood pressure, resting heart rate, arterial stiffness by the means of carotid to femoral pulse wave velocity, carotid intima–media thickness and maximal oxygen uptake (V̇O _2max ) are measured. To this end, a comprehensive set of methods will be used in a prospective manner to provide new knowledge on shift work-induced glucose regulation and CVD risk factors. Ethics and dissemination: All participants provided written informed consent prior to participating in the study, which will adhere to the principles outlined in the Declaration of Helsinki. Ethical approval has been granted by the Norwegian Regional Committee for Medical Research Ethics South-East B (reference # 745702). Dissemination plans include academic and public publications, as well as collaborations with national and regional policy-makers.