AIMS: To describe light exposure, sleep-wake patterns, mood, pain and their relationships in adult medical inpatients.

BACKGROUND: The hospital environment may contribute to patient discomfort by providing a lighting structure that interferes with circadian rhythmicity, sleep, mood and pain.

DESIGN: A descriptive correlational design was used in this preliminary study. METHODS: Between May 2011-April 2012, data were collected from a convenience sample of 23 women and 17 men admitted to a large academically affiliated hospital in the United States. Over 72 hours, light exposure and sleep-wake patterns were continuously measured with wrist actigraph/light meters for each participant. Mood was measured daily using the Profile Of Mood States Brief™ Form. Subjective pain scores were abstracted from medical records.

RESULTS: Light exposure levels were low: mean daytime light intensity was 104·80 lux. Sleep time was fragmented and low: mean 236·35 minutes of sleep/night. Intra-daily stability scores indicated little sleep-wake synchronization with light. Fatigue and total mood disturbance scores were high and inversely associated with light. Pain levels were also high and positively associated with fatigue, but not directly with light exposure. Low light exposure significantly predicted fatigue and total mood disturbance.

CONCLUSION: Medical inpatients were exposed to light levels insufficient for circadian entrainment. Nevertheless, higher light exposure was associated with less fatigue and lower total mood disturbance in participants with pain, suggesting the need for further investigation to determine if manipulating light exposure for medical inpatients would be beneficial in affecting sleep-wake disturbances, mood and pain.