Human Studies

This cross-sectional study examines the association between chronic musculoskeletal pain and foot reaction time (RT) among older community-living adults. Participants were 307 adults aged 71 years and older in the MOBILIZE Boston Study II. Pain severity, interference, and location were measured by the Brief Pain Inventory and a joint pain questionnaire. With participants seated, simple foot reaction time (SRT) was measured as self-selected foot response time to an intermittent light, and choice foot reaction time (CRT) was measured as response time to the light on the corresponding side of the sensored gait mat. We performed multivariable linear regression to determine associations of pain and foot RT, adjusted for sociodemographic and health characteristics, and serially adjusted for cognitive function (MMSE or Trail Making A). Pain severity and interference were associated with slower SRT (p<0.05). Pain severity and knee pain were associated with slower CRT (p<0.05). Adjustment for cognitive measures had little impact on the pain-RT relationship. This signficant relationship was only observed among participants with less education. These results support the idea that chronic pain may lead to slower foot RT, thus could represent a fall hazard in older adults. Neuromotor mechanisms underlying the pain-fall relationship warrant further investigation. PERSPECTIVE: This study provides insights on the mechanisms underlying the pain-fall relationship. Chronic pain may contribute to slower foot reaction time thus increase fall risk in older adults. This may help inform interventions such as stepping training to reduce fall risk in older adults living with chronic pain.

To explore the usefulness and feasibility of a comprehensive vocational rehabilitation (C-VR) program and less comprehensive (LC-VR) program for workers on sick leave due to chronic musculoskeletal pain, from the perspective of patients, professionals, and managers. Semi-structured interviews were held with patients, professionals, and managers. Using topic lists, participants were questioned about barriers to and facilitators of the usefulness and feasibility of C-VR and LC-VR. Thirty interviews were conducted with thirteen patients ( = 6 C-VR,  = 7 LC-VR), eight professionals, and nine managers. All interviews were transcribed verbatim. Data were analyzed by systematic text condensation using inductive thematic analysis. Three themes emerged for usefulness ("patient factors," "content," "dosage") and six themes emerged for feasibility ("satisfaction," "intention to continue use," "perceived appropriateness," "positive/negative effects on target participants," "factors affecting implementation ease or difficulty," "adaptations"). The patients reported that both programs were feasible and generally useful. The professionals preferred working with the C-VR, although they disliked the fixed and uniform character of the program. They also mentioned that this program is too extensive for some patients, and that the latter would probably benefit from the LC-VR program. Despite their positive intentions, the managers stated that due to the Dutch healthcare system, implementation of the LC-VR program would be financially unfeasible. The main conclusion of this study is that it is not useful to have one VR program for all patients with CMP and reduced work participation, and that flexible and tailored-based VR are warranted.Implications for rehabilitationBoth comprehensive and less comprehensive vocational rehabilitation are deemed useful for patients with chronic musculoskeletal pain and reduced work participation. Particular patient factors, for instance information uptake, discipline, willingness to change, duration of complaints, movement anxiety, obstructing thoughts, and willingness to return to work might guide the right program for the right patient.Both comprehensive and less comprehensive vocational rehabilitation are deemed feasible in practice. However, factors such as center logistic (schemes, rooms, professionals available) and country-specific healthcare insurance and sickness compensation systems should foster the implementation of less comprehensive programs.

Chronic musculoskeletal pain affects all aspects of human life. However, mechanisms of its genetic control remain poorly understood. Genetic studies of pain are complicated by the high complexity and heterogeneity of pain phenotypes. Here, we apply principal component analysis to reduce phenotype heterogeneity of chronic musculoskeletal pain at four locations: the back, neck/shoulder, hip, and knee. Using matrices of genetic covariances, we constructed four genetically independent phenotypes (GIPs) with the leading GIP (GIP1) explaining 78.4% of the genetic variance of the analyzed conditions, and GIP2-4 explain progressively less. We identified and replicated five GIP1-associated loci and one GIP2-associated locus and prioritized the most likely causal genes. For GIP1, we showed enrichment with multiple nervous system-related terms and genetic correlations with anthropometric, sociodemographic, psychiatric/personality traits and osteoarthritis. We suggest that GIP1 represents a biopsychological component of chronic musculoskeletal pain, related to physiological and psychological aspects and reflecting pain perception and processing.

When patients suffering from fibromyalgia undergo a therapeutic trial, a non-negligible part of analgesia is not explained by the drug itself. The mechanisms of this non-specific effect need to be understood.

The nociceptive withdrawal reflex (NWR) is used to probe spinal cord excitability in chronic pain states. Here, we used an automated and unbiased procedure for determining the NWR threshold and compared the reflex thresholds and corresponding pain ratings in a well-characterized cohort of fibromyalgia ( = 29) and matched healthy controls ( = 21). Surface electrical stimuli were delivered to the foot in a stepwise incremental and decremental manner. The surface electromyographic activity was recorded from the ipsilateral tibialis anterior muscle. Fibromyalgia patients reported significantly higher scores for psychological distress and pain-related disability and a significantly lower score for perceived state of health compared to the matched controls. The subjective pain ratings were significantly higher in patients. The NWR thresholds were similar to the controls. In the patients, but not in controls, the NWR thresholds and subjective pain ratings were significantly correlated. Our results showed an increased subjective pain sensitivity in fibromyalgia, but we found no evidence for spinal sensitization based on the reflex measures.

The purpose of the ongoing trial is to improve care of older Veterans with chronic low back pain (CLBP, i.e., low back pain for ≥6 months on ≥ half the days). Current CLBP care is limited by being either overly spine-focused or non-specifically prescribed and both approaches frequently lead to suboptimal reduction in pain and improvement in function. Through prior studies we have laid the foundation for a patient-centered approach to care for older Veterans with CLBP in which the spine is a source of vulnerability but not the sole treatment target. The approach considers CLBP a geriatric syndrome, a final common pathway for the expression of multiple contributors rather than a disease of the spine. We describe here the rationale and design of a randomized controlled trial to test the efficacy of an older Veteran-centered approach to CLBP care in "Aging Back Clinics (ABCs)" compared with Usual Care (UC). Three hundred thirty Veterans age 65-89 with CLBP will be randomized to ABCs or UC and followed for 12 months after randomization. We will assess the impact of ABCs on our primary outcome of pain-associated disability with the Oswestry Disability Index at 6 and 12 months, and secondary outcomes of pain intensity, health-related quality of life, balance confidence, mobility and healthcare utilization. If shown efficacious, the approach tested in ABCs has the potential to transform the care of older adults with CLBP by improving the quality of life for millions, reducing morbidity and saving substantial healthcare costs.