Chronic Insomnia With Poor Sleep Efficiency

A 46-year-old woman presents to the sleep clinic with 8 months of difficulty initiating and maintaining sleep, daytime fatigue, and impaired concentration. Polysomnography shows sleep-onset latency of 62 minutes, wake after sleep onset of 98 minutes, and total sleep time of 320 minutes out of 480 minutes time-in-bed. The parameter marked **C** in the diagram—sleep efficiency below 85 percent (calculated as total sleep time divided by time in bed)—is measured at 67 percent. Sleep architecture is preserved with normal REM latency and appropriate N3 proportion. Apnea-hypopnea index is 2.1 events/hour and periodic limb movement index is 4/hour, both normal. Which of the following is the most appropriate first-line management for this patient's condition?