Prevalence and risk factors for insomnia among breast cancer patients on aromatase inhibitors

Insomnia is increasingly recognized as a major symptom outcome in breast cancer; however, little is known about its prevalence and risk factors among women receiving aromatase inhibitors (AIs), a standard treatment to increase disease-free survival among breast cancer patients. A cross-sectional survey study was conducted among postmenopausal women with stage 0-III breast cancer receiving adjuvant AI therapy at an outpatient breast oncology clinic of a large university hospital. The insomnia severity index (ISI) was used as the primary outcome. Multivariate logistic regression analyses were performed to evaluate risk factors. Among 413 participants, 130 (31.5 %) had subthreshold insomnia on the ISI, and 77 (18.64 %) exceeded the threshold for clinically significant insomnia. In a multivariate logistic regression model, clinically significant insomnia was independently associated with severe joint pain (adjusted odds ratio (AOR) 4.84, 95 % confidence interval (CI) 1.71-13.69, P = 0.003), mild/moderate hot flashes (AOR 2.28, 95 % CI 1.13-4.60, P = 0.02), severe hot flashes (AOR 2.29, 95 % CI 1.23-6.81, P = 0.015), anxiety (AOR 1.99, 95 % CI 1.08-3.65, P = 0.027), and depression (AOR 3.57, 95 % CI 1.48-8.52, P = 0.004). Age (> 65 vs. < 55 years; AOR 2.31; 95 % CI 1.11-4.81; P = 0.026) and time since breast cancer diagnosis (< 2 vs. 2-5 years; AOR 1.94; 95 % CI 1.02-3.69; P = 0.045) were also found to be significant risk factors. Clinical insomnia was more common among those who used medication for treating insomnia and pain. Insomnia complaints exceed 50 % among AI users. Clinically significant insomnia is highly associated with joint pain, hot flashes, anxiety and depression, age, and time since diagnosis.