The Relationship Between Light Exposure before Bedtime and Daytime Sleepiness Among People Living With Cognitive Impairment.

While sleep disturbances are common in people living with cognitive impairment, little is known about the influence of evening light exposure on their sleep. The purpose of this study was to examine the relationship between evening light exposure in natural living environment and daytime sleepiness in community residing people living with cognitive impairment. A secondary data analysis was conducted using the baseline data of the Healthy Patterns Clinical Trial. Actiwatch Spectrum Plus was used to collect information on the average white light intensity of 4 hours before sleep for three consecutive days. Multivariate regression analyses were used. Among 173 participants, the average light intensity during evening was 80.25 ± 123.04 lux. After controlling for covariates, greater intensity of light exposure during evening was related to excessive daytime sleepiness ( β = 0.211, p = .004). The results of our study suggest exposure to light during evening may disturb sleep and subsequently influence daytime sleepiness the following day.