The Association of Pain Phenotype with Neuromuscular Impairments and Mobility Limitations Among Older Primary Care Patients: A Secondary Analysis of the Boston Rehabilitative Impairment Study of the Elderly.

Background: Clarifying the relationship between pain phenotypes and physical function in older adults may enhance screening and treatment for functional decline in primary care settings.

Objective: To investigate the association of more severe pain phenotypes with neuromuscular impairments or mobility limitations among older community-dwelling primary care patients.

Design: Cross-sectional analysis.

Setting: The Boston Rehabilitative Impairment Study of the Elderly.

Participants: Adults aged 65 years or older.

Methods: We counted the number of musculoskeletal pain locations (none, single site, multisite, or widespread) using the McGill Pain Questionnaire and identified pain intensity tertiles using the Brief Pain Inventory. Neuromuscular attributes (trunk extensor muscle endurance, and leg speed, strength, strength asymmetry, and range of motion) and mobility (Short Physical Performance Battery [SPPB]) were assessed with performance-based measures. Additionally, self-reported mobility was measured on the Late Life Function and Disability Instrument (LLFDI). For neuromuscular attributes and LLFDI, scores in the lowest tertile indicated neuromuscular impairment or mobility limitations, respectively. For SPPB, a score <7 (of 12) indicated severe mobility limitations.

Results: Among 430 participants (mean age = 77) most were female (68%), white (83%), and had either multisite (50%) or widespread (14%) pain. After adjusting for baseline characteristics, widespread pain (compared to none) was associated with slow leg speed (adjusted odds ratio, 95% confidence interval: aOR = 2.33, 1.03-5.27), limited ankle range of motion (aOR = 2.15, 1.03-4.47) and mobility limitations on LLFDI (aOR = 3.85, 1.81-8.19). Being in the highest pain intensity tertile, versus lowest tertile, was associated with poor trunk extensor muscle endurance (aOR = 2.49, 1.41-4.39), limited ankle range of motion (aOR = 2.15, 1.25-3.71), and mobility limitations on SPPB (aOR = 2.56, 1.45-4.52), and LLFDI (aOR = 4.70, 2.63-8.40).

Conclusions: Among ambulatory, older primary care patients, more severe pain phenotypes are associated with neuromuscular impairments identified on physical testing and mobility limitations on validated measures.