Subjective and objective sleep in children and adolescents : measurement, age, and gender differences

It is important to ascertain the accuracy of children’s and adolescents’ self-reported sleep estimates as they are usually the first (and sometimes only) measure of sleep taken by parents, clinicians, or researchers. In this study, sleep diaries were compared with actigraphy monitoring to investigate the correspondence between measures of sleep in children and adolescents and provide normative data. Differences in age, gender, and school day/weekend were investigated. Sixty-six (21 boys, 45 girls) children and adolescents (11–17 years) wore a wrist actigraphy monitor and completed a 7-day sleep diary. Measures of sleep onset, wake time, wake after sleep onset, and total sleep time were obtained. Less than recommended (9–11 h) amounts of sleep were obtained throughout the week and all participants underestimated the duration of their night wake. Children went to sleep significantly earlier and obtained more sleep than adolescents. Sleep onset and wake time were significantly later on weekends than school days for both age groups. No significant gender differences were found for any objectively measured sleep parameter. Correlations between diary and actigraphy were moderate to high and significant for sleep onset, wake time, and total sleep time. Paired samples t-tests indicated a significant difference between diary and actigraphy scores for all variables except children’s sleep onset. Overall, children and adolescents overestimated their total sleep time by approximately an hour, primarily through an under appreciation of night awakenings

The effects of a 30-min nap during night shift following a prophylactic sleep in the afternoon

The purpose of this study was to investigate the effects of a 30-min nap, during a simulated nightshift environment, when a prophylactic daytime sleep was implemented prior to the night shift. A repeated-measures counter balanced design was used which included two experimental conditions: a 30-min nap and a no nap control. In both conditions subjects obtained a 2-h sleep in the afternoon from 15.00–17.00 hours, which was followed by the night-time nap from 02.30–03.00 hours in a controlled laboratory environment. Post-nap testing was conducted from 03.10 to 07.00 hours. The participants included 22 adults aged from 18–35 years who were good sleepers and did not regularly nap. Subjective alertness (Stanford Sleepiness Scale, Karolinska Sleepiness Scale, Visual AnalogScale), fatigue and vigor (Profile of Mood States), cognitive performance (psychomotor vigilance task, symbol–digit substitution task, letter cancellation task), and objective sleepiness were measured preandpost-nap. The 30-min nap resulted in some impairment of subjective alertness for a brief period (up to 30 min) immediately following the nap when compared to the no nap condition. Following this brief period, alertness and performance were generally improved by the 30-min nap from 04.00 hours until the end of the testing period at 07.00 hours. The results of this study indicate thatwhen a 2-h prophylactic sleep is implemented in the afternoon, a 30-min nap during the subsequentsimulated night shift overall provides a significant countermeasure against sleepiness and performance impairment

Actigraph estimates of the sleep of Australian midwives: the impact of shift work

Midwives often work night and rotating shift schedules, which can lead to sleep disturbances, increased fatigue, and greater likelihood of accidents or errors. This study investigated the sleep of midwives (n ¼ 17) in an Australian metropolitan hospital. Midwives completed work and sleep logbooks and wore wrist actigraphs for 28 days. Midwives worked combinations of morning, afternoon, and/or night shifts on constant (n ¼ 6) or rotating schedules (n ¼ 11). They obtained less than recommended amounts of sleep, getting only 6–7 hr per 24-hr period. Morning shifts were associated with the lowest sleep durations, lowest subjective sleep quality, and highest postsleep fatigue ratings. Despite the significantly higher amount of wake after sleep onset (51 min), the sleep before afternoon shifts had significantly lower postsleep fatigue ratings and was rated as significantly higher quality than sleep before other shifts or days off. Those who were married or living with a partner reported significantly more sleep and lower postsleep fatigue than those who were separated or divorced (p < .05). Seventy-one percent of midwives took naps, primarily before night shifts, with nearly 40% of nightshifts preceded by a nap. Average nap durations were nearly 1.5 hr. Midwives reported feeling moderately to very physically or mentally exhausted on 22–50% of all shifts and days off. Exhaustion was most common on night shift. This study suggests that midwives may be suffering from chronic sleep loss and as a consequence may be at risk of impairments in functioning that accompany fatigue

The relationship between subjective and objective sleepiness and performance during a simulated night-shift with a nap countermeasure

The aim of the present study was to investigate the relationship between perceived and actual sleepinessand performance during a simulated night-shift that included a 30-min night-nap as an on-dutysleepiness countermeasure. Twenty-four healthy young adults (nine males, fifteen females) participatedin a repeated measures design comprising two experimental conditions: no night-nap and 30-min nightnap.Both groups were given a 2-h prophylactic afternoon sleep opportunity (1500e1700 h). Measures ofsubjective sleepiness (Stanford Sleepiness Scale, Karolinska Sleepiness Scale and Visual Analogue Scale),objective sleepiness (sleep latency tests), objective performance (SymboleDigit Substitution Task) andreaction time (Psychomotor Vigilance Task) were taken before the night-nap (0230 h) and at severalintervals post-nap. Timeeseries correlation analyses indicated that subjective sleepiness was lesscorrelated with objective sleepiness and objective performance when participants were given a 30-minnight-nap. However subjective sleepiness and reaction time performance was strongly correlated in bothconditions, and there was no significant difference between the nap and no-nap conditions. Consistentwith previous research, results of the present study indicate that subjective and objective indicators ofsleepiness and performance may not always correspond, and this relationship may be reduced by theinclusion of a night-nap

Author's response to letter to the editor [Refers to: Tomoyuki Kawada, Hiroko Suzuki, Takako Shimizu, Masao Katsumata Polygraphic sleep latency and subjective sleepiness by visual analog scale (VAS): The limitation of VAS Applied Ergonomics, Volume 43, Issue 1, January 2012, Pages 266]

Kawada et al. (2011) report a significant but moderately low correlation (r= -0.44) between subjective and objective sleepiness, measured by responses on a visual analogue scale (VAS) and sleep onset latency (SOL), respectively. Their correlation was calculated using single measures of VAS and SOL associated with a (daytime?) nap collected with 50 participants. The low correlation in this study was used to emphasize the point that VAS determined subjective sleepiness cannot be used as a substitute for objective sleepiness measured by SOL. Indeed, acceptable correlations for good measures of validity would normally have to be >0.70. Therefore, it could be dangerous to predict objective sleepiness at some specific time in a given individual from a single measure of subjective sleepiness