Published papers

Background: A geographical analysis could be employed to uncover social risk factors and interventions linked to chronic pain. Nonetheless, geographical variation in chronic pain across different regions of Japan have not been well explored. This study aims to investigate geographical variation in high-impact chronic pain (HICP), defined as moderate to severe chronic pain, and examine the associated psychological factors at the prefecture level. Methods: A cross-sectional Internet-based survey involving 52,353 participants was conducted to assess chronic pain conditions, stress levels, mood states, educational levels, living status, regions, sleep duration, and exercise habits. A geographical analysis evaluated the prevalence of HICP at the prefecture level, and a multilevel analysis explored the risk factors for HICP at both individual and prefecture levels. Results: The geographical analysis revealed that Fukushima exhibited the highest HICP prevalence (23.2%; z-score = 2.11), Oita ranked second (23.0%; z-score = 2.00), and Okinawa showed the lowest prevalence (14.9%; z-score = −2.45). Geographical maps of Japan indicated that regional-level subjective stress, negative emotions, and short sleep were associated with higher HICP prevalence. In contrast, positive emotions, such as vigor, were associated with lower prevalence. Multilevel analysis revealed a significant improvement in model fit after incorporating psychological factors at the prefecture level (p < 0.001) and identified significant associations between high subjective stress and low vigor at the prefecture level with HICP prevalence (p < 0.001). Conclusion: There are regional differences in HICP prevalence, and at the prefecture level, subjective stress and vigor are associated with HICP.

Background: Chronic pain significantly impacts quality of life and may lead to physical and psychological dysfunction. Although various tools have been developed to assess pain-related conditions, many are composed of time-consuming multi-item questionnaires, limiting practicality in clinical settings. The Multidimensional Evaluation Scale for Patient Impression of Change (MPIC) was developed as a simple, retrospective tool to assess multiple domains targeted in interdisciplinary pain management. This study evaluated the reliability and validity of the Japanese MPIC in patients with chronic non-cancer pain. Methods: We recruited 101 participants from the Interdisciplinary Pain Center at Keio University Hospital between August 2022 and September 2024. Pretreatment measures included pain intensity, disability, catastrophizing, self-efficacy, psychological distress, and sleep quality. Baseline assessments encompassed pain intensity, disability, catastrophizing, self-efficacy, psychological distress, and sleep quality. Psychological distress was evaluated using the Hospital Anxiety and Depression Scale (HADS) for the initial cohort of 35 participants and the Kessler Psychological Distress Scale (K6) for the subsequent 66 participants. Following the intervention, participants completed the MPIC, in addition to reassessments of pain intensity, disability, catastrophizing, self-efficacy, psychological distress (HADS or K6), and sleep quality. Retesting the MPIC was performed in a small subgroup of 20 participants for test–retest reliability analysis. Confirmatory factor analysis (CFA), average variance extracted (AVE), Pearson’s correlations with pain-related measures, Cronbach’s alpha, and intraclass correlation coefficients (ICC) were used to assess construct validity, convergent validity, criterion validity, internal consistency, and reliability. Results: CFA indicated marginal fit (CFI = 0.86, RMSEA = 0.23, SRMR = 0.06), with factor loadings from 0.49 to 0.91. AVE supported convergent validity (0.58). Internal consistency was excellent (Cronbach’s alpha = 0.93), and ICC was moderate (0.52). MPIC domains correlated significantly with changes in pain intensity, disability, catastrophizing, self-efficacy, sleep, and psychological distress (p < 0.05), supporting criterion validity. Conclusions: The Japanese MPIC provides preliminary evidence of validity and reliability, with acceptable internal consistency, marginal structural fit, and moderate test–retest reliability. These findings suggest that the MPIC may serve as a concise retrospective instrument for assessing multidimensional treatment outcomes within interdisciplinary pain management programs for chronic non-cancer pain.

Pain is a global health problem that leads to sedentary behavior and tends to cause negative emotion. In contrast, exercise is widely recommended for a health promotion, while pain often worsens with physical activity. Although exercise therapy is often prescribed to people with pain, the mechanisms of exercise effect on pain remains unclear. In this study, we tried to identify a universal association factor between regular exercise and pain intensity utilizing a cross-sectional web-based survey involving 52,353 adult participants from a large national study conducted in Japan. Using principal component analysis, we uncovered a mediation model of exercise effect on pain through psychological components. Analyses were performed in half of the population with pain (n = 20,330) and validated in the other half (n = 20,330), and showed that high-frequency exercise had a significant association with reduction in pain intensity. We also found Negative Affect and Vigor, two psychological components, are fully associating the exercise effect on pain (indirect effect = − 0.032, p < 0.001; association proportion = 0.99) with a dose-dependent response corresponding to the frequency of exercise. These findings were successfully validated (indirect effect of high-frequency exercise = − 0.028, p < 0.001; association proportion = 0.85). Moreover, these findings were also identified in subpopulation analyses of people with low back, neck, knee pain, and the tendency of the exercise effect on pain was increased with older people. In conclusion, the effect of exercise on pain is associated with psychological components and these association effects increased in parallel with the frequency of exercise habit regardless pain location.

The COVID-19 pandemic has increased germ aversion, an aversive affective response to a high likelihood of pathogen transmission. While psychological factors are associated with chronic pain, the relationship between germ aversion and chronic pain remains unexplored. This study aimed to examine the relationship between germ aversion and new-onset and prognosis of chronic pain using longitudinal data collected during the COVID-19 pandemic. We conducted web-based surveys of full-time workers at baseline and after three months. Data were collected on demographic characteristics, psychological factors, and chronic pain. Germ aversion was assessed using a modified Perceived Vulnerability to Disease scale. We analyzed responses from 1265 panelists who completed the survey twice. The prevalence of chronic low back pain (CLBP) and chronic neck and shoulder pain (CNSP) was associated with sex, short sleep duration, psychological distress, loneliness, and germ aversion. Stratified analyses showed that germ aversion was a risk factor for CLBP at three months in both individuals with and without CLBP at baseline, and for CNSP at three months in those with CNSP at baseline, even after adjustment for confounders. In conclusion, this preliminary study suggests that high germ aversion is a risk factor for CLBP and CNSP in young and middle-aged workers.

Background. The biopsychosocial mechanism by which exercise leads to improvement in chronic low back pain (CLBP) remains unstudied. This prospective cohort study was performed to examine the effectiveness of exercise on pain, disability, and psychological status for CLBP. We also tested path analytic models in which changes in these variables were included. Methods. CLBP patients who visited the Interdisciplinary Pain Center of Keio University Hospital from July 2018 to April 2020 were included. The propensity score matching was performed between patients who underwent exercise (the exercise group) and those who did not (the control group). At the first visit and at the 3-month follow-up, pain (Numerical Rating Scale (NRS)), disability (Pain Disability Assessment Scale (PDAS)), and psychological status (Pain Self-Efficacy Questionnaire (PSEQ), and Pain Catastrophizing Scale (PCS)) were assessed. Changes in pain and disability at the follow-up were compared between the groups. The relationships between changes in pain, disability, and psychological variables were examined using Pearson's correlation and mediation analysis. Results. A significantly larger decrease in the PDAS was observed in the exercise group (N = 49) than in the control (N = 49) (p<0.05). Increased PSEQ scores were significantly correlated with decreased NRS scores in both groups. In the exercise group, decreased PDAS fully mediated the relationship between increased PSEQ and decreased NRS (P<0.05). Conclusion. Exercise improved disability, and the improved disability by exercise mediated the effect of increased self-efficacy on pain relief in CLBP patients.