Are Poor Sleepers Afraid of the Dark? A Preliminary Investigation

Abstract

No studies have investigated whether those with poor sleep are aware of being uncomfortable in the dark via subjective inquiry, and no study has evaluated whether poor sleepers have increased fear in the dark using objective indices (e.g., a validated startle paradigm). Good and poor sleepers (N = 108) completed questionnaires about their level of discomfort with the dark and were evaluated for an increased startle reflex by measuring eyeblink latency via electrooculogram in response to unexpected noise in the dark and the light. Participants listened to bursts of unexpected white noise, while in counterbalanced light/dark conditions. Relative to good sleepers, more poor sleepers reported increased discomfort in the dark. There was a significant lighting × time × sleeper status interaction for eyeblink latency. Relative to the first trial in the dark, eyeblink latency in good sleepers increased in the second dark exposure; suggesting habituation in the dark. Eyeblink latency in poor sleepers did not decrease. Thus, poor sleepers reported being uncomfortable in the dark and they remained more easily startled in the dark over the course of the study. It is unclear if the dark may predispose people to sleep problems, or if sleep problems sensitize poor sleepers to fear darkness.