Human Studies

Musculoskeletal (MSK) pain conditions are a leading cause of pain and disability internationally and a common reason to seek health care. Accurate prediction of recurrence for health care seeking due to MSK conditions could allow for better tailoring of treatment. The aim of this project was to characterize patterns of recurrent physical therapy seeking for MSK pain conditions and to develop a preliminary prediction model to identify those at increased risk for recurrent care seeking.

Stimulation of zona incerta in rodent models has been shown to modulate behavioral reactions to noxious stimuli. Sensory changes observed in Parkinsonian patients with subthalamic deep brain stimulation suggest that this effect is translatable to humans. Here, we utilized the serendipitous placement of subthalamic deep brain stimulation leads in 6 + 5 Parkinsonian patients to directly investigate the effects of zona incerta stimulation on human pain perception. We found that stimulation at 20 Hz, the physiological firing frequency of zona incerta, reduces experimental heat pain by a modest but significant amount, achieving a 30% reduction in one fifth of implants. Stimulation at higher frequencies did not modulate heat pain. Modulation was selective for heat pain and was not observed for warmth perception or pressure pain. These findings provide a mechanistic explanation of sensory changes seen in subthalamic deep brain stimulation patients and identify zona incerta as a potential target for neuromodulation of pain.

Low back pain (LBP) is one of the most common musculoskeletal disorders, causing significant personal and social burden. Current research is focused on the processes of the central nervous system (particularly the sensorimotor system) and body perception, with a view to developing new and more efficient ways to treat chronic low back pain (CLBP). Several clinical tests have been suggested that might have the ability to detect alterations in the sensorimotor system. These include back-photo assessment (BPA), two-point discrimination (TPD), and the movement control tests (MCT). The aim of this study was to determine whether the simple clinical tests of BPA, TPD or MCT are able to discriminate between nonspecific CLBP subjects with altered body perception and healthy controls.

Chronic pain is a significant co-morbidity of burn injury affecting up to 60% of survivors. Currently, no treatments are available to prevent chronic pain after burn injury. Accumulating evidence suggests that omega-3 fatty acids (O3FA) improve symptoms across a range of painful conditions. In this study, we evaluated whether low peritraumatic levels of O3FA predicts greater pain severity during the year after burn injury. Burn survivors undergoing skin autograft were recruited from three participating burn centers. Plasma O3FA (n=77) levels were assessed in the early aftermath of burn injury using liquid chromatography/mass spectrometry and pain severity was assessed via the 0-10 numeric rating scale for 1 year following burn injury. Repeated-measures linear regression analyses were used to evaluate the association between peritraumatic O3FA concentrations and pain severity during the year following burn injury. Peritraumatic O3FA concentration and chronic pain severity were inversely related; lower levels of peritraumatic O3FA predicted worse pain outcomes (β=-.002, p=.020). Future studies are needed to evaluate biological mechanisms mediating this association and to assess the ability of O3FA to prevent chronic pain following burn injury.

The characteristics of self-reported functional limitations among older United States (US) adults with pain are currently unknown. This cross-sectional study aimed to determine the characteristics associated with functional limitations among non-institutionalized older (≥50 years) US adults with pain using 2017 Medical Expenditure Panel Survey (MEPS) data. Eligible subjects were alive for the calendar year, aged ≥50 years, and experienced pain within the past four weeks. Hierarchical logistic regression models were utilized to determine significant characteristics associated with functional limitations (outcome variable; yes, no). Functional limitations included difficulty with bending, stooping, climbing stairs, grasping objects, lifting, reaching overhead, standing for long periods of time, or walking. Extrapolation of national data values was possible by adjusting for the complex MEPS design. We found approximately 22 million of the 57 million older US adults (≥50 years) who reported pain had a functional limitation in 2017. Characteristics associated with functional limitations included: gender, race, ethnicity, employment status, marital status, pain intensity, physical health, number of chronic conditions, and frequent exercise status. Knowledge of characteristics associated with functional limitations may provide an opportunity to identify and resolve gaps in patient care among this population.

To determine how many persons with knee pain have subsequent pain resolution and what factors are associated with resolution, focusing especially on types of physical activity.

To examine the prevalence of comorbid conditions in a nationwide population of men and women with IC/BPS utilizing a more heterogeneous sample than most studies to date.