Effects of pain management on work ability in aging workers with chronic musculoskeletal pain: a cross-sectional study

The main finding of this study indicated a significant association between pain management and work ability. Specifically, pharmacological pain treatment and combined pharmacological and non-pharmacological pain treatments were more prevalent among individuals with lower WAI scores, as detailed in Table 2. Additionally, this study found that participants with reduced work ability reported higher pain severity and interference, leading to increased reliance on medication (Fig. 2). Moreover, this study identified several factors influencing work ability among aging workers. Risk factors for reduced work ability included pain severity, pain interference, knee pain, lower back pain, underlying conditions such as dyslipidemia and hypertension, and promptly returning home when experiencing pain outdoors. Conversely, the protective factors encompassed continuous sitting for at least two hours.

The majority of the participants in this study was women, which is consistent with a previous study. Rawdeng et al. reported a positive correlation between sex and the WAI score²⁵, whereas no such relationship was found in this study. The discrepancy in these findings could be attributed to differences in the studied populations (office workers vs. predominantly agricultural workers in this cohort) and due to the setting of this study, which was conducted in a tertiary hospital, where most of the participants who sought treatment because of MSP were female participants²⁶. Our study participants were of an average age of 58 years, which is relatively high compared with the average age of 43 years in another study²⁵. In this study, the overall median pain-severity subscale score was 4.0 and that of pain interference was 2.6, aligning with the findings of a previous study in older adults²⁷. Therefore, women tend to have a higher WAI score than men in certain populations.

This study found that both pain severity and pain interference were strongly associated with WAI, and individuals with poor work ability had higher pain severity and pain interference. Previous research has found that the ability to move, sleep quality, and mental health of the participants are affected by severe pain and pain interference^7,28. This study revealed that, as pain levels increased, participants often required more intensive treatment, leading them to seek additional medical care and reduce their work frequency. Participants with poor work ability in this study exhibited higher levels of pain severity and pain interference and were more likely to rely on pharmacological treatments. Particularly, the use of topical analgesics and adjuvants was significantly higher among participants with poor WAI scores, likely due to their availability as over-the-counter medications in Thailand, which made them more accessible to aging workers. Conversely, some individuals with pain managed by returning home immediately, a behavior associated with increased sick leave and reduced working hours. This coping strategy emerged as a significant risk factor for lower work ability in this study.

Additionally, this study identified a significant association between poor WAI scores and hypertension. Previous research suggests that chronic pain reduces baroreflex sensitivity and disrupts vagal circuit function²⁹. Furthermore, Bruehl et al. demonstrated that, among individuals with chronic pain, elevated blood pressure correlates with increased pain intensity³⁰. Consistent with these findings, other studies indicate that effective pain management may simultaneously alleviate both pain and hypertension, highlighting the importance of comprehensive treatment approaches³¹.

In the ergonomics dimension, this study found that participants with poor-to-moderate WAI scores tended to present a higher rate of computer use for at least 4 h and bending forward for carrying objects than those with poor work ability. Both long-term sitting and forward trunk bending have been proposed as important risk factors for work-related musculoskeletal injury in every age group, especially for low back pain^32,33,34. In previous occupational studies, the OR for low back pain and sciatica increased with exposure to awkward postures and prolonged sitting³⁵. This is due to mechanisms such as increased lumbar muscle fatigue³⁷, which heightens the stress on passive spinal structures (ligaments and intervertebral discs) and leads to discomfort and pain in the back and leg area^36,37. However, a recent umbrella review contradicted this finding, indicating that sitting for longer than 2 h does not significantly elevate the risk of low back pain³⁸. The present study identified sitting for more than 2 h as a protective factor against poor work ability. This can be explained by the observation that some aging workers, who experience less pain, are able to sit continuously, leading to better work performance due to no interruptions caused by pain. Consistent with this finding, participants in the excellent WAI group reported being able to maintain the same posture during work without pain, in contrast to those with poor or moderate WAI, who experienced greater discomfort.

Although no statistically significant difference was observed, participants in the excellent WAI group demonstrated a higher utilization rate of non-pharmacological treatments, such as physical therapy, Thai traditional medicine, and acupuncture, compared to those in the poor-to-moderate WAI group. Moreover, a significant association was identified between the combined use of pharmacological and non-pharmacological treatments and WAI, highlighting the potential benefits of incorporating non-pharmacological approaches. The underlying mechanisms for this observation remain unclear; however, these treatments are considered to leverage the combined effects of physical stimuli and movement-related techniques to alleviate pain and improve function. Further research is required to explore the effect of these protocols on the work abilities of workers experiencing pain.

The clinical importance of this study lies in emphasizing the need for effective pain management to reduce pain and improve work ability among aging workers with chronic MSP. Pharmacological treatments, particularly adjuvants and topical analgesics, were commonly used by those with higher pain levels and lower work ability. Additionally, the combination of pharmacological and non-pharmacological treatments was significantly associated with improved work ability in this cohort. This study underscores the importance of ensuring access to appropriate pain-management strategies for aging workers to sustain their work performance. Furthermore, addressing chronic non-communicable diseases, particularly hypertension and dyslipidemia, is crucial for enhancing overall health and maintaining occupational productivity in aging workers.

The strengths of this study need to be emphasized. First, this study categorized aging workers into four categories, poor, moderate, good, and excellent, based on their WAI score. This categorization differed from that in previous studies that typically employed a binary approach (poor-to-moderate and good-to-excellent work ability). Second, this study used ordinal regression analysis for data analysis for robust insights into ordinal data relationships, whereas this method is less commonly used in similar studies. Another notable strength of our study was the primary data collection from patients at a tertiary hospital, which ensured accurate diagnosis and medication information from medical records. The current study has some limitations. First, this was a cross-sectional study, which was unable to establish the long-term effects of pain management on work ability. Second, the hospital-based data collection may have resulted in a participant sample primarily consisting of individuals seeking treatment, such as a predominance of female patients. Future studies should consider community-based settings to better represent diverse populations and conduct subgroup analyses to explore the associations between various factors and WAI. Third, this study utilizes the Thai version of the PCI, which was developed as a pilot version by our research team. Since the results have not yet been published, the ongoing publication process may require validation. Finally, this study could not identify any pain-coping strategies associated with high work performance based on the Pain Coping Inventory questionnaire. Future research employing qualitative methods, such as in-depth interviews, is strongly recommended for providing deeper insights into the coping strategies used by aging workers who maintain high levels of work performance.