The Impact of Sleep Inertia on Physical, Cognitive, and Subjective Performance Following a 1- or 2-Hour Afternoon Nap in Semiprofessional Athletes

From physiological awakening to pathological sleep inertia: Neurophysiological and behavioural characteristics of the sleep-to-wake transition

Sleep inertia refers to the transient physiological state of hypoarousal upon awakening, associated with various degrees of impaired neurobehavioral performance, confusion, a desire to return to sleep and often a negative emotional state. Scalp and intracranial electro-encephalography as well as functional imaging studies have provided evidence that the sleep inertia phenomenon is underpinned by an heterogenous cerebral state mixing local sleep and local wake patterns of activity, at the neuronal and network levels. Sleep inertia is modulated by homeostasis and circadian processes, sleep stage upon awakening, and individual factors; this translates into a huge variability in its intensity even under physiological conditions. In sleep disorders, especially in hypersomnolence disorders such as idiopathic hypersomnia, sleep inertia may be a daily, serious and long-lasting symptom leading to severe impairment. To date, few tools have been developed to assess sleep inertia in clinical practice. They include mainly questionnaires and behavioral tests such as the psychomotor vigilance task. Only one neurophysiological protocol has been evaluated in hypersomnia, the forced awakening test which is based on an event-related potentials paradigm upon awakening. This contrasts with the major functional consequences of sleep inertia and its potentially dangerous consequences in subjects required to perform safety-critical tasks soon after awakening. There is a great need to identify reproducible biomarkers correlated with sleep inertia-associated cognitive and behavioral impairment. These biomarkers will aim at better understanding and measuring sleep inertia in physiological and pathological conditions, as well as objectively evaluating wake-promoting treatments or non-pharmacological countermeasures to reduce this phenomenon.

Daytime naps improve afternoon power and perceptual measures in elite rugby union athletes-a randomized cross-over trial

Daytime naps are used by elite athletes in both training and match-day settings. Currently, there are limited interventional studies on the efficacy of napping on physical performance in elite team-sport athletes. Therefore, the objective was to investigate the effect of a daytime nap (<1 hour) on afternoon performance of peak power, reaction time, self-reported wellness, and aerobic performance in professional rugby union athletes. A randomized cross-over design was carried out among 15 professional rugby union athletes. Athletes performed nap (NAP) and no nap (CON) conditions on two occasions, separated by 1 week. Baseline testing of reaction time, self-reported wellness, and a 6-second peak power test on a cycle ergometer were completed in the morning, followed by 2 × 45-minute training sessions, after which athletes completed the NAP or CON condition at 1200 hours. Following the nap period, baseline measures were retested in addition to a 30-minute fixed-intensity interval cycle and a 4-minute maximal effort cycling test. A significant group × time interaction was determined for 6-second peak power output (+157.6 W, p < 0.01, d = 1.53), perceived fatigue (-0.2 AU, p = 0.01, d = 0.37), and muscle soreness (-0.1 AU, p = 0.04, d = 0.75) in favor of the NAP condition. A significantly lower perceived exertion rating (-1.2 AU, p < 0.01, d = 1.72) was recorded for the fixed-intensity session in favor of NAP. This study highlights that utilizing daytime naps between training sessions on the same day improved afternoon peak power and lowered perceptions of fatigue, soreness, and exertion during afternoon training in professional rugby union athletes.

Association of sleep status with depressive state in centenarians: Evidence from Hainan centenarian cohort

OBJECTIVE

The objective of this study is to analyze the association between sleep quality, sleep duration, sleep patterns, and depressive states among centenarians due to the crucial impact of depression on the well-being of elderly individuals, particularly the oldest. Recognizing easily identifiable manifestations and risk factors is essential since the onset of depressive states tends to be insidious.

METHODS

The baseline data from the China Hainan Centenarians Cohort Study (CHCCS) served as the basis for this study. Questionnaire surveys were conducted to obtain research indicators, with depressive states evaluated using the GDS-15 scale and sleep quality evaluated using the Pittsburgh Sleep Quality Index (PSQI). Logistic regression was employed to describe the association between sleep status and depressive states.

RESULTS

A total of 994 centenarians, with an age range of 100-116 years and a mean age of 102.77 ± 2.75 years, were included in this study. Among these participants, 815 were female, accounting for 82.0 %. After adjustment, the odds ratio (OR) for the association between poor sleep quality and depressive states was 2.07 (95 % CI: 1.54-2.77) compared to those with normal sleep quality. Additionally, there were associations between depressive states and both nighttime sleep duration and total sleep duration. After adjustment, the strongest association between depressive state and sleep patterns was found for those who had >9 h of nighttime sleep and ≥2 h of daytime sleep (OR = 1.80, 95%CI: 1.02-3.16). Moreover, compared to centenarians with 7-9 h of sleep duration and good sleep quality, the highest odds ratio (OR = 3.44, 95%CI: 2.18-5.43) for the association between depressive states and sleep duration ≤7 h and poor sleep quality was observed.

CONCLUSION

The findings of this study indicate that there is an association between poor sleep quality and depressive states in centenarians. Furthermore, both sleep quality and long/short total sleep duration are associated with depressive states in this population. Therefore, special attention should be given to the psychological state of elderly individuals with short sleep duration and poor sleep quality in order to prevent depression and minimize its negative impact on their overall health.

Is daytime napping an effective strategy to improve sport-related cognitive and physical performance and reduce fatigue? A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To estimate the association between daytime napping and cognitive and physical sport performance and fatigue after normal sleep and partial sleep deprivation (less sleep duration than necessary).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

The PubMed, Scopus, Web of Science, Cochrane Central, SportDiscus and PsycINFO databases.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials on the effect of daytime napping on sport performance and fatigue available from inception to 2 December 2022. Standardised mean differences (SMD) and their 95% compatibility intervals (CI) were estimated with the DerSimonian-Laird method through random effect models.

RESULTS

In the 22 included trials, 291 male participants (164 trained athletes and 127 physically active adults) aged between 18 and 35 years were studied. When performed after a normal night of sleep, napping from 12:30 hours to 16:50 hours (with 14:00 hours being the most frequent time) improved cognitive (SMD=0.69, 95% CI: 0.37 to 1.00; I²=71.5%) and physical performance (SMD=0.99, 95% CI: 0.67 to 1.31; I²=89.1%) and reduced the perception of fatigue (SMD=-0.76, 95% CI: -1.24 to -0.28; I²=89.5%). The positive effects of napping were also confirmed after partial sleep deprivation. Overall, the benefits were higher with a nap duration between 30 and <60 min and when the time from nap awakening to test was greater than 1 hour.

CONCLUSIONS

After a night of normal sleep or partial sleep deprivation, a daytime nap between 30 and <60 min has a moderate-to-high effect on the improvement of cognitive performance and physical performance and on the reduction of perceived fatigue.

PROSPERO REGISTRATION NUMBER

CRD42020212272.