LAUSR

OBJECTIVE Patients with chronic insomnia are prone to long-term use of hypnotics. Reported risk factors include aging, female sex, and comorbid psychiatric disorders. However, most previous studies have been cross-sectional cohort studies. METHOD We conducted a retrospective cohort study using medical service payment data for 330,000 people to determine the duration of prescription of hypnotics and the risk factors for long-term use. We followed up 3981 patients (2382 M, 1599 F, age 40.3 ± 12.4 years) who were prescribed hypnotics for the first time between April 2005 and March 2008. RESULTS Of these 3981 patients, 59.6% were prescribed hypnotics for only 1 month, 11.3% were prescribed hypnotics for 2 consecutive months, and 10.1% of patients continued receiving prescriptions for the entire 12-month observation period. In multiple logistic time-dependent Cox analyses, use of antidepressants, mean dose of hypnotics, and advanced age were significantly associated with long-term use of hypnotics (p < 0.01). In an analysis of the association between long-term use of hypnotics and prescribed dosage, high monthly dose, advanced age, and department of first visit were significantly associated with long-term use (p < 0.01). CONCLUSION These clinical indicators may be effective for early identification of patients with insomnia who are at high risk of developing physical dependence on hypnotics.