Effect of Aromatase Inhibitor Therapy on Sleep and Activity Patterns in Early-stage Breast Cancer.

INTRODUCTION: Adherence to aromatase inhibitor (AI) therapy is poor, often because of treatment-emergent side effects, including musculoskeletal symptoms, fatigue, and insomnia. In the present analysis, we examined the sleep patterns and daytime function both objectively using actigraphy and subjectively using validated questionnaires in women initiating AI therapy.

PATIENTS AND METHODS: Postmenopausal women with stage 0-III hormone receptor-positive breast cancer who were initiating AI therapy were eligible. The patients wore actigraphy devices for 10 consecutive days and completed questionnaires at baseline before the initiation of AI and after 3 months of AI therapy. Associations between the baseline demographics and symptoms, changes in patient-reported outcomes and actigraphy measures from baseline to 3 months of AI therapy and discontinuation of AI therapy were examined using sign tests, logistic regression models, Spearman's correlation, and linear mixed models.

RESULTS: Forty-two patients (86%) completed the baseline assessments and 23 patients (47%) completed both the baseline and the 3-month assessments. Objectively measured daytime function as measured by total daytime activity decreased during the 3 months after starting AI (232,566 activity count vs. 204,205 activity count; P = .023), and the decrease was more evident in women with higher baseline physical function. Reduced daytime activity correlated with increased fatigue (ρ = -0.49; P = .017).

CONCLUSION: Daytime function decreased after initiation of AI therapy and correlated moderately with increased fatigue, although no association was identified with changes in pain or sleep quality. Additional studies are required to understand why function is reduced, which could have implications for interventions to improve patient tolerance of, and persistence with, AI therapy.