Vulnerability to stress-related sleep disturbance and hyperarousal

Study Objectives: To determine the presence of a hypothesized trait vulnerability to sleep disturbance and hyperarousal. Design: Polysomnographic assessment of sleep in response to stress during a first night in the laboratory and subsequent physiologic arousal. Participants: One hundred and four individuals (46% men, mean age 40.4 +/- 12.9 years) drawn from a population-based sample. Interventions: Individuals were exposed to a first night in the laboratory. Measurements and Results: Participants completed a Likert-scale questionnaire, consisting of 27 items, that assesses sleep disturbance in response to commonly experienced stressful situations. Factor analytic techniques identified a single 9-item factor that was representative of the construct of "stress-related" vulnerability to sleep disturbance. Reliability of the resulting 9-item scale was high (Cronbach's alpha = .83). Individuals with higher scores on this scale, the Ford Insomnia Response to Stress Test (FIRST, median split), had a lower sleep efficiency (P = .001), as well as an increased latency to stage 1 sleep (P = .001) and persistent sleep (P = .002) on the first night of nocturnal polysomnography. Moreover, these high-scoring individuals showed increased arousal as evidenced by an elevated sleep latency on the Multiple Sleep Latency Test compared to individuals with low FIRST scores. Importantly, after controlling for current and past insomnia, the differences between individuals scoring high and low on the FIRST in terms of nocturnal sleep and daytime arousal remained significant. Other stages of sleep (stage 2, slow-wave, and rapid eye movement sleep) were not different between the groups. Conclusions: These results showing a relationship between FIRST scores and nocturnal polysomnography and Multiple Sleep Latency Test scores have 3 potential implications: (1) the data demonstrate a characteristic that relates to vulnerability to stress-related sleep disturbance as manifested by a first night in the laboratory; (2) the elevated latencies on the Multiple Sleep Latency Test in these individuals, despite significantly disturbed sleep, support the notion of physiologic hyperarousal in these individuals and suggests they may be predisposed to developing chronic primary insomnia; and (3) the vulnerability identified may underlie vulnerability to transient sleep disturbance associated with other sleep-disruptive factors.