The insensitivity of sleep to an unfamiliar sleeping environment in patients with insomnia disorder

Sleeping in an unfamiliar environment, such as a sleep laboratory, is thought to disturb sleep in healthy individuals and could express a hyperarousal state called the first night effect. Insomnia disorder (ID) is a highly prevalent health problem characterized by increased arousal during the night and daytime. Whether or not a similar phenomenon occurs in patients with ID is unclear. This study aimed to investigate the effect of an unfamiliar environment on the sleep of patients with ID.

In an unfamiliar sleep laboratory, polysomnographic recording testing was performed for two consecutive nights in patients with ID and age- and sex-matched healthy control subjects (HC). We collected sleep diaries and questionnaires regarding sleep, medical conditions, psychological status, and health history. Sleep continuity and architecture in both groups were compared and analyzed for two consecutive nights.

Participants with ID (n = 39)  and HC (n = 35) demonstrated differentially poor sleep on laboratory adaptation after exposure to the sleep laboratory. Patients with ID had longer rapid eye movement (REM) latency on the first night than on the second sleep night. HC showed increased duration and percentage of N1, decreased duration and percentage of N3, and decreased REM percentage during initial nights compared to subsequent nights. The other sleep variables showed no differences between the first and second sleep nights in patients with ID and HC.

An unfamiliar sleep environment does not aggravate the disruption of sleep continuity and sleep architecture but only affects the REM latency in patients with ID compared with HC.