Naturally occurring circadian rhythm and sleep duration are related to executive functions in early adulthood

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Excerpt

Executive functions (EFs) are considered the central control systems for complex behaviour, such as attention, planning and goal‐setting, inhibitory abilities and cognitive flexibility. EFs can be defined both as permanent characteristics of an individual (Friedman et al., 2016) and as fluctuating test performance affected by states such as stress (Shields et al., 2016), sleep deprivation (Rossa et al., 2014), alcohol consumption (Day et al., 2015), medication (Moeller et al., 2014) and mood (Cotrena et al., 2016).
As a somewhat stable characteristic of an individual, EFs can be evaluated with self‐ratings such as the Behavior Rating Inventory of Executive Function (BRIEF) (Roth et al., 2005). Regarding performance‐based EFs, there are several objective tests targeting their different aspects, such as attention (Conners, 2004), working memory (Reitan, 1958) and inhibitory control (Bohnen et al., 1992). A recent review concluded that there are two different constructs of EF: self‐reports are mainly indices of goal pursuit, whereas performance‐based EF tests estimate the efficiency of cognitive abilities, and the constructs correlate only modestly (0.19) with each other (Toplak et al., 2013).
Several experimental sleep deprivation studies have reported domain‐specific associations with performance‐based EFs (Banks and Dinges, 2007; Jackson et al., 2013; Lo et al., 2012). Some studies have reported slower reaction times, but no weakening of inhibitory control in sleep‐deprived subjects (Bratzke et al., 2012; Cain et al., 2011; Dixit and Mittal, 2015), while others reported poorer performance in tasks requiring higher executive functions, such as risk‐taking (Rossa et al., 2014) or divergent thinking (Vartanian et al., 2014), but with no effect on reaction times.
However, sleep deprivation occurs not only in experimental studies, but also under natural conditions, which provides greater ecological validity to study the consequences for cognitive functions. In particular, as young adults are more prone to have a later circadian rhythm (Duffy et al., 2015) and as there are several studies reporting a growing prevalence of both longer and shorter sleep (Bin et al., 2013) there is an increasing need to investigate the outcomes of naturally occurring sleep in this age group. Later circadian rhythm may result in shorter sleep duration, daytime sleepiness and an increasing amount of weekend catch‐up sleep (Juda et al., 2013). Circadian misalignment and both long and short sleep duration are all associated with several detrimental outcomes such as depression (Wittmann et al., 2006), higher risk for cardiovascular diseases (Wong et al., 2015) and poorer overall wellbeing (De Souza and Hidalgo, 2015; Rutters et al., 2014); it is still unknown how these associations are manifested in everyday executive functioning.
There are few epidemiological studies linking young adults’ naturally occurring sleep with EF, but the findings are consistent. In a study (Wilckens et al., 2014) of 112 adults, shorter objectively measured sleep duration associated with poorer task‐switching performance in both younger (mean age 23 years) and older (mean age 63 years) age groups. In a study of 154 young adults, subjective complaint of poor sleep quality associated with a deficit in sustained attention (Gobin et al., 2015). Self‐reported circadian misalignment, or preference towards eveningness, has been reported to associate with lower self‐regulation abilities (Digdon and Howell, 2008; Tangney et al., 2004). Additionally, performance in several objective EF tests is associated with circadian rhythm and time of day, suggesting that sleep timing may play a part in performance‐based EF (Hahn et al., 2012). Similarly, irregular sleep, as night‐to‐night variation in sleep, has been shown to associate with more frequent attention problems (Whiting and Murdock, 2016) and subjective wellbeing (Lemola et al., 2013).
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