Light is considered the dominant environmental cue, or zeitgeber, influencing the sleep-wake cycle. Despite recognizing the importance of light for our well-being, less is known about the specific conditions under which light is optimally associated with better sleep. Therefore, a systematic review was conducted to examine the association between the amount and timing of light exposure in relation to sleep outcomes in healthy, community-dwelling adults. A systematic search was conducted of four databases from database inception to June 2016. In total, 45 studies met the review eligibility criteria with generally high study quality excepting for the specification of eligibility criteria and the justification of sample size. The majority of studies involved experimental manipulation of light (n=32) vs observational designs (n=13). Broad trends emerged suggesting that (1) bright light (>1000 lux) has positive implications for objectively assessed sleep outcomes compared to dim (<100 lux) and moderate light (100-1000 lux) and (2) bright light (>1000 lux) has positive implications for subjectively assessed sleep outcomes compared to moderate light (100-1000 lux). Effects due to the amount of light are moderated by the timing of light exposure such that, for objectively assessed sleep outcomes, brighter morning and evening light exposure are consistent with a shift in the timing of the sleep period to earlier and later in the * Corresponding author. ndautovich@vcu.edu. (N.D. Dautovich).
Intraindividual variability is an often understudied aspect of health outcomes research that may provide additional, complementary information to average values. The current paper aims to further our understanding of intraindividual variability in health research by presenting the results of a daily diary study of sleep and pre-sleep arousal. Pre-sleep arousal is often implicated in poor sleep outcomes, although the arousal–sleep association is not uniform across age groups. The examination of intraindividual variability in different age groups may provide a more complete understanding of these constructs, which, in turn, can inform future research. The overall objectives of the current study are to quantify the amount of intraindividual variability in pre-sleep arousal and sleep and to examine age differences in this variability. A sample of older (n=50) and younger (n=50) adults recruited from North Central Florida and online completed 14-consecutive-day diaries assessing pre-sleep arousal and sleep outcomes. Significant age differences were found for sleep and pre-sleep arousal; older adults displayed poorer, more variable sleep for the majority of sleep outcomes, and higher levels of pre-sleep arousal than younger adults. The high amount of intraindividual variability has implications for the assessment of pre-sleep arousal and sleep across age groups.
The purpose of this study is twofold: (a) to determine whether daily or overall cognitive and somatic arousal better predict sleep and (b) to investigate age differences in the arousal-sleep relation. Fifty younger and 50 older adults completed the Pre-Sleep Arousal Scale and sleep diaries for 14 consecutive days. Analyses revealed mean arousal may better predict sleep regardless of age. However, daily arousal represents an important avenue of research as it may uncover lagged or coupling effects in the arousal-sleep relation. Significant age differences in the arousal-sleep relation suggest age-dependent associations between the type of arousal and sleep. Implications for assessment of sleep in older and younger adults are discussed.
This study explored the association of engagement in pleasant events and global sleep quality, as well as examined the intermediary roles of positive affect and depressive symptoms in this association. Data were derived from the Midlife in the United States-II study. The sample consisted of 1,054 community-dwelling adults. Participants completed the Pittsburgh Sleep Quality Index and indicated the frequency and enjoyableness of experiences on a positive events scale. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Positive affect was measured using the Mood and Symptoms Questionnaire. Regression analyses indicated more frequent engagement in pleasant events was associated with better global sleep quality. Depressive symptoms, but not positive affect, partially mediated the association between pleasant events and global sleep quality. The findings suggest that behavioral engagement in pleasant events may be related to global sleep quality via depressive symptoms, but not positive affect. These findings highlight the potential for engagement in pleasant activities to influence both mood and sleep.
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