A Pharmacoepidemiological Indicator for Detecting Potential Regional Overuse of Hypnotics in Japan: A Cross-Sectional Study

Objectives The main objective of this study is to examine how environmental and demographic factors shape regional prescription patterns of circadian-related hypnotics, and to develop a pharmacoepidemiological indicator for detecting potential regional overuse. Methods A nationwide ecological cross-sectional study was conducted using 2022 data from all 47 prefectures of Japan. Population-adjusted prescription volumes of ramelteon, suvorexant, and lemborexant were obtained from the National Database of Health Insurance Claims. Environmental (annual sunlight duration and ultraviolet index) and demographic (aging rate and outpatient clinic density) variables were extracted from governmental statistics. Pearson correlation and multivariable linear regression analyses were conducted, and residuals were geographically visualized to identify regional deviations from model expectations. Results Ramelteon and suvorexant prescriptions were significantly associated with shorter sunlight duration and higher aging rates (r = -0.64 and -0.61, both p < 0.001). In multivariable analysis, sunlight duration and aging rate independently predicted prescription volumes (adjusted R² = 0.46), with improved performance (adjusted R² = 0.51) after exclusion of high-influence outliers. Residual analysis revealed that unexplained positive deviations were concentrated in urban prefectures, suggesting locally elevated prescribing tendencies. Conclusions Regional prescription volumes of circadian-related hypnotics can, to some extent, be anticipated from environmental determinants such as sunlight duration. The proposed indicator-based pharmacoepidemiological framework may help identify regions at risk of potential overuse and guide climate-sensitive strategies for optimizing hypnotic use in older adults.