A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults.

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 day, respectively. For subjectively assessed sleep outcomes, brighter light delivered in the morning was associated with self-reported sleep improvements and brighter evening light exposure was associated with worse self-reported sleep.

The Associations Between Dispositional Mindfulness, Sense of Control, and Affect in a National Sample of Adults.

Objectives: The present study examined factors associated with better affective experiences across the life span, extending existing research to older adults. Specifically, we investigated dispositional mindfulness and sense of control as predictors of affect and sense of control as a potential mediator of the mindfulness-affect associations. Method: We hypothesized that dispositional mindfulness mediated by sense of control would predict affective outcomes. An archival analysis of a sample of 4,962 adults, aged 28 to 84 years, was conducted using the Midlife in the U.S. national survey (MIDUS-II). Exploratory analyses were conducted with age as a moderator in all associations. Results: Greater dispositional mindfulness predicted more positive and negative affect irrespective of age. Dispositional mindfulness did not predict sense of control. Greater sense of control predicted more positive and less negative affect, and these associations were significantly moderated by age. Sense of control did not mediate the dispositional mindfulness-affect associations. Discussion: The present study extends existing research on the dispositional mindfulness-positive affect association to older ages. The sense of control and positive and negative affect associations are enhanced and buffered, respectively, at older ages, indicating that the association between control and affect differs by age.