Objectives: Research suggests that medication adherence improves quality of life. This study explored the influence of social support (SS) on the relationship between comorbidity medication adherence (CMA) and health-related quality of life for patients with cancer.
Methods: Patients with metastatic breast, colorectal, or lung cancer undergoing cancer treatment in 2015 and at least 1 comorbid condition were mailed surveys to assess SS, CMA, and Healthy Days. The Medical Outcomes Study Social Support Survey Instrument captured patient-perceived SS. The SS scale ranges from 0 to 100 and was collapsed into 2 categories: poor/fair (<60-80) and good (>80). CMA was assessed using the 8-point Morisky Medication Adherence Scale and was collapsed into 2 categories: low (<6) and high (≥6). The Centers for Disease Control and Prevention’s Healthy Days Measure assessed self-reported health-related quality of life as the number of unhealthy days (unHD) in the past 30 days. Results were reported as mean (standard deviation); statistical significance was assessed by t test. Negative-binomial regression was used to assess the relationship between CMA and SS on unHD. Results were presented as rate ratios (95% CIs).
Results: Of 7432 patients surveyed, 25% (n = 1847) responded. Respondents were 67% female, and 88% were Medicare beneficiaries, with a mean age of 69.2 ± 9.2 years. Good SS was reported by 63% of patients; fair/poor SS by 37% of patients. High CMA was reported in 70% of the cohort, and low CMA in 30%. The average number of unHD was 14.0 ± 11.9. Regression analysis revealed the association between CMA and unHD was moderated by SS. In a main effects regression model, low CMA (1.18 [1.03, 1.35]; P = .0155), but not low SS (1.12 [0.99, 1.27]; P = .0694), was associated with unHD. When tested for a moderator effect, unHD was regressed on CMA/SS interaction along with main effects. Evidence of moderation was observed in the interaction between SS and CMA (P = .0393) and no association with unHD by SS (P = .6819) or CMA (P = .5895). With low SS, low CMA increased unHD by 33% (1.33 [1.01-1.74]), whereas with high SS, low CMA increased unHD by only 5% (1.05 [0.88, 1.2]).
Conclusions: Patients with low CMA experienced more unHD than those with high CMA. The increase in unHD attributed to low CMA is further amplified by low SS. This finding suggests that a greater importance should be placed on patients’ social and caregiver resources.
Note: This work was supported by Genentech, Inc.