Abstract and Introduction
Abstract
Objective To examine the impact of sleep duration on emotional functioning and cognitive performance in children.
Methods 32 children (8–12 years) wore actigraphs for 3 weeks. Following a week of typical sleep, each child was randomly assigned to go to bed 1 hr earlier for 4 nights (Long Sleep) or 1 hr later for 4 nights (Short Sleep) relative to their typical bedtime. Each child then completed the opposite condition. After each week, emotional and cognitive functioning were assessed using objective and subjective measures.
Results Results revealed impaired functioning in the Short- relative to the Long-Sleep condition on measures of positive affective response, emotion regulation, short-term memory, working memory, and aspects of attention.
Conclusions Results suggest that even modest differences in sleep duration over just a few nights can have significant consequences for children's daytime functioning. These findings demonstrate the important impact of sleep duration on children's daytime functioning.
Introduction
Sleep problems are common in children, affecting ~25% of the population (Owens, 2007). Furthermore, a number of reports suggest that children's total sleep duration has shown a steady decline over the past several decades (Dollman, Ridley, Olds, & Lowe, 2007; Iglowstein, Jenni, Molinari, & Largo, 2003; Matricciani, Olds, Blunden, Rigney, & Williams, 2012). A poll of >600 American parents of school-aged children found that although children are estimated to need 10–11 hr of sleep nightly (Meltzer & Mindell, 2006), they averaged only 9.0–9.5 hr (National Sleep Foundation, 2004). However, it is also important to acknowledge the lack of empirical foundation for recommendations for sleep duration (Matricciani, Olds, & Williams, 2011; Matricciani et al., 2012).
Given the high prevalence of sleep problems and the suggestion that many children sleep less than is recommended, it is important to understand the impact of sleep duration on their daytime functioning. The daytime consequences of sleep loss have been well documented in adults (e.g., Walker & Stickgold, 2006), and studies examining adolescent populations are accumulating (see Beebe, 2011 for review). There is, however, only limited pediatric literature examining the impact of sleep duration on daytime functioning in pre-adolescents (for review, see Sadeh, 2007).
A number of correlational studies have associated poor sleep or the presence of sleep disorders with symptoms of emotional dysregulation in children (Fredriksen, Rhodes, Reddy, & Way, 2004; Gregory, Rijsdijk, & Eley, 2006; Kurnatowski, Putyński, Łapienis, & Kowalska, 2008), but these cannot establish causality. Longitudinal studies suggest that poor sleep precedes the emergence of emotional problems in children (e.g., depression and low self-esteem ratings, Fredriksen et al., 2004; anxiety, depression, and aggressive behavior, Gregory, Van der Ende, Willis, & Verhulst, 2008). Studies involving experimental manipulations of sleep are much more limited. Talbot, McGlinchey, Kaplan, Dahl, and Harvey (2010) found that adolescents who were restricted to 6.5 hr sleep for one night and 2 hr the following night reported less positive affect, but no change in negative affect. Using an affective response task, Leotta, Carskadon, Acebo, Seifer, and Quinn (1997) found that 8–12-year-old children reported higher levels of negative emotions following sleep restriction.
Similarly, correlational studies relating sleep and cognitive functioning in children found that early school start times (which result in shortened sleep durations; Wahlstrom, 2002) are linked to poor academic performance (e.g., Wolfson & Carskadon, 1998), and poor sleep is linked to impaired attention (Gruber et al., 2007; Sadeh, Gruber, & Raviv, 2002; Vriend et al., 2012) and memory (Steenari et al., 2003). The effects of experimental sleep restriction in children on cognition have also been studied, and most reports describe impaired functioning in some domains: Arithmetic and word memory tasks (Carskadon, Harvey, & Dement, 1981a); verbal creativity, learning new abstract concepts, and abstract thinking (Randazzo, Muehlbach, Schweitzer, & Walsh, 1998); inattention, as assessed by a research assistant (Fallone, Acebo, Arnedt, Seifer, & Carskadon, 2001); simple reaction time (Sadeh, Gruber, & Raviv, 2003); teacher-reported academic problems and severity of attention problems (Fallone, Acebo, Seifer, & Carskadon, 2005; Gruber, Cassoff, Frenette, Wiebe, & Carrier, 2012); and vigilance and sustained attention (Gruber et al., 2011; Peters et al., 2009).
Studies of memory and attention have shown that performance correlates with sleep duration (Gruber et al., 2009; Steenari et al., 2003) and that these domains are particularly vulnerable to experimentally shortened sleep (Carskadon, Harvey, & Dement, 1981b; Fallone et al., 2001, 2005; Gruber et al., 2011; Sadeh et al., 2003). A few studies, however, have reported that sleep loss does not impair performance on some tests of memory and attention (Carskadon et al., 1981a; Fallone et al., 2001; Randazzo et al., 1998). Most studies have used acute overnight sleep restriction. It is important, however, to understand the impact of more chronic, and limited sleep loss, which many children experience.
We enlisted parents and children to lengthen sleep for four consecutive nights (1 hr earlier than their habitual bedtime: Long-Sleep condition) and shorten sleep for four consecutive nights (1 hr later than their habitual bedtime: Short-Sleep condition) while children slept at home and otherwise maintained their usual activities. These manipulations resulted in sleep duration differences during the 2 weeks that might realistically occur spontaneously among children. Based on previous research, we predicted that shorter sleep would increase negative emotions, decrease positive emotions, and impair emotion regulation, mood, and cognitive performance (e.g., memory, attention).