Risk of Insomnia Disorder in Japanese Cancer Patients: A Matched Cohort Study Using Employer‐Based Health Insurance Claims Data

Background Insomnia is a common clinical symptom that significantly impairs quality of life (QOL) and it frequently occurs in cancer patients. However, the risk of insomnia in Japanese cancer patients compared with cancer‐free patients has not yet been studied. Aims This study evaluated the association between cancer diagnosis and the risk of insomnia disorder in the Japanese health insurance claims database. Methods A population‐based matched cohort study was performed comparing cancer patients with cancer‐free patients. The primary outcome was the time to onset of insomnia disorder in cancer and cancer‐free patients. Multivariate analyses were performed to determine hazard ratio (HR) for all patients and for each cancer type. Results A total of 36,230 cancer patients and 362,300 cancer‐free patients were enrolled in this study. The median age was 53 years. Among cancer patients, the time to onset of insomnia disorder was significantly shorter than that of cancer‐free patients (stratified log‐rank testing; p < 0.001). In the multivariate analysis, the HR of cancer status (HR 3.39; 95% CI 3.28–3.49) was largest. In the subgroup analysis, the insomnia disorder risk was highest in patients with esophageal cancer, multiple cancers, gallbladder/biliary tract cancer, and bone and articular cartilage cancer. Conclusions This study shows that Japanese cancer patients have a higher risk of developing insomnia disorder compared with cancer‐free patients. The risk was especially high in cancer types which have a poor prognosis or impair the QOL of patients. These findings highlight the importance of assessing insomnia disorder frequently in cancer patients and providing interventions when it is needed.