Medical inpatients with pain: light exposure and sleep patterns may matter

Adults admitted to the hospital as medical inpatients (for non-surgical diagnostics and intervention) often experience pain. The lighting structure in the physical environment in which they convalesce may contribute to their discomfort by interfering with circadian rhythmicity and sleep. A predictive correlational study was done to examine the relationships among light exposure, sleep-wake patterns, and pain in medical inpatients. Light exposure and sleep-wake patterns were measured with wrist actigraph/light meters worn by participants continuously for 72 hours. Fatigue was measured by a participant’s subjective answer on a Likert-type scale. Pain scores and demographics were obtained from participants’ medical records. The convenience sample included 23 females, 17 males, mean age 50 years. Light exposure levels (lux): daytime M=104.8 (SD=131.1); nighttime M=7.1 (SD=7.0). Sleep (minutes): nighttime M=236.3 (SD=72.3); daytime M=161.0 (SD=81.4). Actigraph fragmentation calculations indicated highly disturbed sleep: M=9.4 epoch disturbances per 8 hours (SD=5.5). Pain scores: M=6.0/10.0 (SD=1.9). Fatigue scores: M=2.9/4.0 (SD=1.0). A significant inverse relationship was found between light exposure and fatigue (r=-.34, p<.05), and a positive relationship between fatigue and pain (r=.34, p<.05). Light exposure significantly predicted fatigue, R2=.11, R2 adj=.09, F(1,38)=4.86, p<.05. Fatigue significantly predicted pain, R2=.11, R2 adj=.09, F(1,38)=4.84, p<.05. The inverse relationship between light exposure and fatigue indicates that the higher the light exposure, the less fatigue even in a low light environment where participants experienced light exposure levels insufficient to support circadian entrainment. These study results provide a basis for future investigations to examine lighting interventions as a novel way to improve circadian rhythmicity, fatigue, sleep-wake patterns, and consequently pain in hospitalized adults. Supported by a grant from the American Society for Pain Management Nursing.