title: Short Daytime Naps Briefly Attenuate Objectively Measured Sleepiness Under Chronic Sleep Restriction Epidemiology of sports-related concussion in seven US high school and collegiate sports The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep patterns and injury occurrence in elite Australian footballers.
abstract: Study Objectives Napping is a useful countermeasure to the negative effects of acute sleep loss on alertness . The efficacy of naps to recover from chronic sleep loss is less well understood . Methods Following 2 baseline nights ( 10 hours ' time-in-bed ) , participants were restricted to 7 nights of 5-hour sleep opportunity .  Ten adults participated in the No-Nap condition , and a further 9 were assigned to a Nap condition with a daily 45-minute nap opportunity at 1300 h. Sleepiness was assessed using the multiple sleep latency test and a visual analogue scale at 2-hour intervals . Both objective and subjective indexes of sleepiness were normalized within subject as a difference from those at baseline prior to sleep restriction . Mixed-effects models examined how the daytime nap opportunity altered sleepiness across the day and across the protocol . Results Short daytime naps  attenuated sleepiness due to chronic sleep restriction for up to 6 - 8 hours after the nap . Benefits of the nap did not extend late into evening . Subjective sleepiness demonstrated a similar short-lived benefit that emerged later in the day when objective sleepiness already returned to pre-nap levels . Neither measure showed a benefit of the nap the following morning after the subsequent restriction night . Conclusions These data indicate a short daytime nap may attenuate sleepiness in chronic sleep restriction , yet subjective and objective benefits emerge at different time scales . Because neither measure showed a benefit the next day , the current study underscores the need for careful consideration before naps are used as routine counter measures to chronic sleep loss Background The epidemiology of sports-related concussion is not well-described in the literature . This paper presents a descriptive epidemiology of concussion in seven high school and collegiate sports . Methods We used the data from Concussion Prevention Initiative ( CPI ) , which enrolled 8905 athletes at 210 high schools and 26 colleges in a prospect i ve cohort study of 7 sports ( football , men ’s and women ’s soccer , men ’s and women ’s lacrosse , and men ’s and women ’s ice hockey ) between 1999 and 2001 . Injury risks and injury rates were used to characterize the incidence of concussion , and changes in symptoms over time were described . Results A total of 375 concussions were observed . The incidence of concussion was highest in football , followed by women ’s lacrosse , men ’s lacrosse , men ’s soccer , and women ’s soccer ( only 10 ice hockey teams were included , too few to quantify incidence ) . The rate of incident concussion was strongly associated with history of concussion in the previous 24 months ( rate ratio = 5.5 ; 95 % CI : 3.9 , 7.8 , for 2 or more concussions relative to no previous concussion ) . The most common symptoms at time of injury were headache ( 87 % ) , balance problems/dizziness ( 77 % ) , and feeling “ in a fog ” ( 62 % ) . Loss of consciousness and amnesia were present in relatively few cases ( 9 and 30 % ) . The most common mechanism of injury was collision with another player . Conclusions Sports-related concussions present with a diverse range of symptoms and are associated with previous concussion history OBJECTIVES To inform the debate over whether human sleep can be chronically reduced without consequences , we conducted a dose-response chronic sleep restriction experiment in which waking neurobehavioral and sleep physiological functions were monitored and compared to those for total sleep deprivation . DESIGN The chronic sleep restriction experiment involved r and omization to one of three sleep doses ( 4 h , 6 h , or 8 h time in bed per night ) , which were maintained for 14 consecutive days . The total sleep deprivation experiment involved 3 nights without sleep ( 0 h time in bed ) . Each study also involved 3 baseline ( pre-deprivation ) days and 3 recovery days . SETTING Both experiments were conducted under st and ardized laboratory conditions with continuous behavioral , physiological and medical monitoring . PARTICIPANTS A total of n = 48 healthy adults ( ages 21 - 38 ) participated in the experiments . INTERVENTIONS Noctumal sleep periods were restricted to 8 h , 6 h or 4 h per day for 14 days , or to 0 h for 3 days . All other sleep was prohibited . RESULTS Chronic restriction of sleep periods to 4 h or 6 h per night over 14 consecutive days result ed in significant cumulative , dose-dependent deficits in cognitive performance on all tasks . Subjective sleepiness ratings showed an acute response to sleep restriction but only small further increases on subsequent days , and did not significantly differentiate the 6 h and 4 h conditions . Polysomnographic variables and delta power in the non-REM sleep EEG-a putative marker of sleep homeostasis -- displayed an acute response to sleep restriction with negligible further changes across the 14 restricted nights . Comparison of chronic sleep restriction to total sleep deprivation showed that the latter result ed in disproportionately large waking neurobehavioral and sleep delta power responses relative to how much sleep was lost . A statistical model revealed that , regardless of the mode of sleep deprivation , lapses in behavioral alertness were near-linearly related to the cumulative duration of wakefulness in excess of 15.84 h ( s.e . 0.73 h ) . CONCLUSIONS Since chronic restriction of sleep to 6 h or less per night produced cognitive performance deficits equivalent to up to 2 nights of total sleep deprivation , it appears that even relatively moderate sleep restriction can seriously impair waking neurobehavioral functions in healthy adults . Sleepiness ratings suggest that subjects were largely unaware of these increasing cognitive deficits , which may explain why the impact of chronic sleep restriction on waking cognitive functions is often assumed to be benign . Physiological sleep responses to chronic restriction did not mirror waking neurobehavioral responses , but cumulative wakefulness in excess of a 15.84 h predicted performance lapses across all four experimental conditions . This suggests that sleep debt is perhaps best understood as result ing in additional wakefulness that has a neurobiological " cost " which accumulates over time OBJECTIVES To examine the potential relationship between sleep duration and efficiency and injury incidence in elite Australian footballers . DESIGN Prospect i ve cohort study . METHODS Australian footballers ( n=22 ) from one AFL club were studied across the 2013 competitive season . In each week sleep duration and efficiency were recorded via actigraphy for 5 nights ( the 3 nights preceding a game , the night of the game and the night after the game ) . Injury incidence was monitored and matched with sleep data : n=9 players suffered an injury that caused them to miss a game . Sleep in the week of the injury ( T2 ) was compared to the average of the previous 2 weeks ( T1 ) . A two-way repeated measures ANOVA was used to determine any effect of sleep duration and efficiency on injury . Significance was accepted at p<0.05 . RESULTS Injury incidence was not significantly affected by sleep duration , sleep efficiency or a combination of these factors . Analysis of individual nights for T2 versus T1 also showed no differences in sleep quality or efficiency . However , a main effect for time was found for sleep duration and efficiency , with these being slightly , but significantly greater ( p<0.05 ) at T2 ( 437±61min and 82±7 % ) than T1 ( 414±64min and 79±7 % ) . CONCLUSIONS No significant effect of sleep duration and efficiency on injury occurrence was found in elite Australian footballers
target: Conclusions : Chronic lack of sleep in adolescents is associated with greater risk of sports and musculoskeletal injuries .
  Current evidence can not yet definitively determine the effect of acute lack of sleep on injury rates .
background: Background : Although sleep has been identified as an important modifiable risk factor for injury , the effect of decreased sleep on sports injuries in adolescents is poorly studied .
  The objective of this study was to quantitatively and qualitatively review published literature to examine if a lack of sleep is associated with sports injuries in adolescents and to delineate the effects of chronic versus acute lack of sleep .