Shift work, low-grade inflammation, and chronic pain: a 7-year prospective study

Abstract

Objectives We investigated prospective associations of shift work with chronic pain and C‐reactive protein (CRP), an indicator of inflammation. Furthermore, we elucidated CRP as a possible mediator and/or moderator of effects of shift work on pain. Methods Data from a 7 years follow‐up study were analyzed (N = 2323). Shift work and chronic pain of “neck/shoulder”, “arm/hand”, “upper back”, “low back”, “hip/leg/feet”, and “other regions” were measured by questionnaires. “Chronic widespread pain”, “number of chronic pain sites”, and “any chronic pain” were computed. CRP was measured in serum samples. Logistic and Poisson regressions were conducted. Mediation was assessed by casual mediation analyses and moderation by the Relative Excess Risk due to Interaction (RERI). Results Shift work was not associated with any chronic pain variable and no mediation was detected. CRP was associated with low back pain, hip/leg pain, and “number of pain sites”, and also with the combination of shift work and CRP of 1–2.99 mg/L (compared to: no shiftwork and CRP < 1). Additionally, shiftwork and CRP 1–2.99 mg/L was associated with risk of “any chronic pain” (OR: 1.76, 95% CI: 1.12, 2.85), which was not associated with CRP alone. Moderation analyses suggested the risks for “any chronic pain” and “number of pain regions” increased when individuals with elevated CRP worked shifts—beyond what the separate effects of CRP and shift would suggest. Conclusions We found no evidence of shift work in general affecting CRP or chronic pain. However, shift work and elevated CRP combined may influence chronic pain.

Association between urinary phthalate levels and chronic pain in US adults, 1999–2004: A nationally representative survey

“…Some studies suggest a potential role of mitochondrial ROS and oxidative stress in neuropathic and inflammatory pain ( 33 , 34 ). A slight increase of unspecific inflammatory markers, such as C-reactive protein (CRP), was associated with low back pain, hip/leg pain, and the number of pain sites, as shown in a follow-up study done over seven years ( 35 ). In comparison, PAEs exposure was also reported to increase oxidative stress markers ( 17 , 36 , 37 ).…”

Human immune and metabolic biomarker levels, and stress-biomarker associations, differ by season: Implications for biomedical health research

“…Although few variables are likely to confound relations between time of year and an outcome specifically, there may be many measured and unmeasured confounds of mediators and moderators of seasonality. For example, shift work may increase both perceived stress and markers of inflammation ( Christensen et al, 2021 ; Matre et al, 2021 ; Velazquez-Kronen et al, 2023 ). Travel across time zones ( Doane et al, 2010 ) and other factors that affect biorhythms not measured in the present study likely also impact patterns of seasonal change in biomarkers.…”

Shift work is associated with 10-year incidence of atrial fibrillation in younger but not older individuals from the general population: results from the Tromsø Study

“…Another factor that may have affected our results is the so-called ‘healthy worker effect’: individuals with existing health issues may opt for jobs with conventional working schedules, and shift workers who develop new health issues (potentially as a consequence of shift work) may stop doing shift work as a result. 5 8 Because shift workers are less at risk to begin with, the risk associated with shift work may be underestimated. 29 In our study, shift workers less often had hypertension (despite higher prevalence of obesity and smoking) compared with non-shift workers, which could be indicative of the healthy worker effect.…”

“…Shift work, which is generally defined as any type of work that is done outside of conventional daytime working schedules, 4 is becoming increasingly common due to increasing demands from the so-called ‘24-hour society’ that has emerged in recent years. 5 6 In 2015, approximately 21% of workers in the European Union reported doing shift work, compared with 17% in 2005 and 2010. 7 Previous studies have demonstrated that shift work is associated with adverse cardiovascular outcomes, in particular coronary artery disease and stroke.…”