Background/Purpose: Osteoarthritis of the knee (OAK) affects nearly 14 million older adults and more than half are diagnosed with hypertension (HTN). Cognitive behavior therapy (CBT) has demonstrated inconsistent effectiveness on OAK symptoms. The purpose of this secondary analysis was to examine if patient adherence to CBT influences its effectiveness for OAK outcomes (pain, function, stiffness, health-related quality of life [HRQoL], and fatigue) among people with comorbid HTN.

Methods: This longitudinal comparative study analyzed data from a randomized controlled trial of a CBT plus physical activity (Staying Active with Arthritis or STAR) intervention vs. a control intervention in older adults with OAK and HTN. Participants who completed at least one session of the STAR or control interventions were included (n=172). STAR intervention consisted of 15 sessions including six weekly face-to-face physical therapy (lower extremity exercise and walking) sessions and nine biweekly telephone sessions for support (mean adherence was 10.8±0.6). Patient adherence was derived by dichotomizing participants into adherers who completed 15 STAR sessions (n=37) and non-adherers who completed < 15 STAR sessions (n=51). Control intervention consisted of 15 telephone sessions on senior health topics (n=84). Pain, function, and stiffness were measured by WOMAC Osteoarthritis Index subscales, HRQoL was measured by Short Form-36v2 Physical Component Summary and Mental Component Summary, and fatigue was measured by Brief Fatigue Inventory at baseline, immediate post-intervention, and 6 months post-intervention. Linear mixed modeling controlling for baseline outcome value, time, significant demographics and medical factors (age, sex, race, marital status, education, employment status, duration of OAK and HTN, and number of comorbidities) were used to compare within-group and between-group differences in the outcomes.

Results: The sample was primarily female (n=126, 73.3%), non-Hispanic white (n=130, 75.6%), married/partnered (n=86, 50.0%), and not working/retired (n=86, 50.0%) with mean (±SD) age of 65.0±8.0 years. On average, the duration of OAK and HTN was 11.3±9.3 and 13.6±9.2 years, respectively, and the number of comorbidities was 8.4±3.6. Regardless of adherence group, STAR participants had significant improvement in pain, function, and stiffness from baseline to immediate post-intervention and 6 months post-intervention. Compared with adherers, controls reported significantly greater knee pain (b=0.69, p=0.035) and a trend for worse function (b=2.24, p=0.051), but the difference between non-adherers and controls was not significant. There was no significant difference between adherers and non-adherers in pain, function, stiffness, HRQoL, and fatigue.

Conclusion: Both adherers and non-adherers showed improved OAK-specific outcomes of pain, function, and stiffness, but not HRQoL and fatigue. There was no difference in OAK outcomes between adherers and non-adherers or between non-adherers and controls. Adherers had less knee pain and a trend for better function compared to controls. Patient adherence to intervention sessions was a significant factor influencing the effectiveness of the intervention.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationships-among-adherence-and-patient-outcomes-in-a-cognitive-behavioral-plus-physical-activity-intervention-for-older-adults-with-osteoarthritis-and-hypertension/