Short Afternoon Nap Research Articles

Effects of a short afternoon nap on cognitive and psychomotor functions of non-sleep-deprived subjects

Objectives: A short nap is a countermeasure against fatigue; however, the possibility of sleep inertia (SI) persists. Understanding its effects on piloting mental functions is crucial for the implementation of strategic naps. Material and Methods: Fifty well-slept healthy male volunteers, aged 24–45 years (mean ± standard deviation: 33 ± 5.5 years), participated in this study. Psychomotor aspects, executive control functions, and higher-order cognitive functions were studied. Psychometry was conducted using simple reaction time test (SRTT), Stroop test (ST), and digit symbol substitution test (DSST). An afternoon nap of 30-min served as the intervention. Pre-nap data were collected at 0800 h and at 1330 hours (h). After 1400 h, participants were allowed to sleep for 30-min. Data were collected for 2 h post-nap, every 15-min during the 1st h and every 30-min during the 2nd h. Results: SRTT response time was longer (p < 0.0001) in the post-nap period, and this effect persisted for 2-h. However, there was no post-nap change (p = 0.0527) in response accuracy. There was no significant change (p = 0.379) in the Stroop effect after the nap. The DSST, response time remained unchanged immediately post-nap (p = 0.367) but shortened and persisted after 30-min post-nap (p = 0.0088) for 2-h. The accuracy of responses in the DSST was unaffected. Conclusion: An afternoon nap of 30 minutes is sufficient to produce SI, thus impairing the motor speed. However, the accuracy of psychomotor and cognitive functions was unaffected. Meanwhile, the speed of higher-order cognitive functions was improved. Although the findings caution about the policy of using short naps as a countermeasure against fatigue in aviation, it is recommended to further validate the research after addressing the limitations mentioned in the study.

Effects of a brief afternoon nap on declarative and procedural memory

The relationship between sleep and memory consolidation has not been fully revealed. The current study aimed to investigate how a brief afternoon nap contributed to the consolidation of declarative and procedural memory by exploring the relationship between sleep characteristics (i.e., the durations of sleep stages and slow oscillation, slow-wave activity, and spindle activity extracted from sleep) and task performance and the relationship between delta, theta, alpha, and beta bands extracted from wake during task performance and task performance. Twenty-three healthy young adults underwent a paired associates learning task and a sequential finger-tapping task with easy and difficult levels and were tested for memory performance before and after the intervention (i.e., an about 30-min nap or stay awake). Electroencephalogram (EEG) signals were continously recorded during the whole experiment. Results revealed that a short afternoon nap improved movement speed for the procedural memory task, regardless of the task difficulty, but unaffected the performance on the declarative memory task. Besides, the improvement in movement speed for the easy procedural memory task was positively correlated with slow-wave activity (SWA) during non-rapid-eye-movement (NREM) sleep but negatively correlated with slow oscillation and spindle activity during sleep stage 2 and NREM sleep, and the improvement in the difficult procedural memory task correlated positively with SWA during NREM sleep. Moreover, performance on the easy declarative and procedural memory tasks was negatively correlated with the relative power of alpha or theta; whereas the alpha band was positively correlated with the difficult declarative memory performance. These findings suggested that a brief afternoon nap with NREM sleep would benefit procedural memory consolidation but not declarative memory; such contribution of napping to memory consolidation would be either explained by the sleep characteristics or physiological arousal during performing tasks; task difficulty would moderate the relationship between the declarative memory performance and EEGs during task performance.

Lifestyle-Related Factors and Total Mortality in a Mediterranean Prospective Cohort

Lifestyle-related habits have a strong influence on morbidity and mortality worldwide. This study investigates the association between a multidimensional healthy lifestyle score and all-cause mortality risk, including in the score some less-studied lifestyle-related factors. Participants (n=20,094) of the Seguimiento Universidad de Navarra cohort were followed up from 1999 to 2018. The analysis was conducted in 2019. A 10-point healthy lifestyle score previously associated with a lower risk of major cardiovascular events was applied, assigning 1 point to each of the following items: never smoking, moderate-to-high physical activity, moderate-to-high Mediterranean diet adherence, healthy BMI, moderate alcohol consumption, avoidance of binge drinking, low TV exposure, short afternoon nap, time spent with friends, and working ≥40 hours per week. During a median follow-up of 10.8 years, 407 deaths were documented. In the multivariable adjusted analysis, the highest category of adherence to the score (7-10 points) showed a 60% lower risk of all-cause mortality than the lowest category (0-3 points) (hazard ratio=0.40, 95% CI=0.27, 0.60, p<0.001 for trend). In analyses of the healthy lifestyle score as a continuous variable, for each additional point in the score, a 18% relatively lower risk of all-cause mortality was observed (adjusted hazard ratio=0.82, 95% CI=0.76, 0.88). Adherence to a healthy lifestyle score, including some less-studied lifestyle-related factors, was longitudinally associated with a substantially lower mortality rate in a Mediterranean cohort. Comprehensive health promotion should be a public health priority.

Siesta and Risk for Ischemic Stroke: Results from a Case-Control Study.

Background and objectives: Siesta, which is a short afternoon nap, is a habit that is commonly practiced in the Mediterranean and tropical areas. Data on the association between siesta and coronary artery disease has been conflicting. A protective effect has been demonstrated in the countries that commonly practice siesta, but a harmful effect has been observed in the countries that infrequently practice the siesta habit. Information on the association between siesta and ischemic stroke has been, however, lacking. Hence, the purpose of our study was to determine the effect of siesta on ischemic stroke. Materials and Methods: This was a case-control study, conducted on the patients with acute ischemic stroke who came for their first follow-up visit to the neurology clinic. Controls were randomly selected from the patients visiting the neurology clinic on the same day as the patients with ischemic stroke. In addition to basic demographics and the occurrence of established stroke risk factors, information about siesta practice was also collected from both groups. A multivariate logistic regression analysis was utilized to determine the relationship between siesta practice and ischemic stroke. Results: A total of 206 patients were recruited from the neurology clinic of King Khalid university hospital; of which only 194 subjects were included in the analysis (98 ischemic stroke cases and 96 controls). The mean age of the participants was 59.68 ± 13.75 years and 98 (50.52%) were male. Interestingly, 43% of the whole study cohort practiced regular siesta. However, when compared to the stroke population, the control group practiced siesta more frequently (30% vs. 56%). In a multivariate logistic regression analysis, hypertension, diabetes mellitus, excess body weight (body mass index > 25 kg/m2) and dyslipidemia were found to increase the risk of ischemic stroke (OR 2.12, 95% CI: 1.02–4.66, p = 0.005; OR 2.72, 95% CI: 1.94–4.88, p = 0.014; OR 2.94, 95% CI: 1.5164–5.7121 p = 0.0014; OR 3.27, 95% CI: 2.42–5.199, p ≤ 0.001, respectively). On the contrary, the practice of regular siesta lowered the risk of ischemic stroke (OR 0.58, 95% CI: 0.3551–0.9526, p = 0.031). Conclusions: Siesta was associated with a reduced risk for the occurrence of ischemic stroke. Large prospective longitudinal studies should be conducted to verify the protective effect of siesta on stroke.

Lifestyles and the risk of depression in the “Seguimiento Universidad de Navarra” cohort

BackgroundLifestyles are involved in the pathogenesis of depression and many of these factors can be modified for the potential prevention of depression. Our aim was to assess the association between a healthy-lifestyle score, that includes some less-studied lifestyle indicators, and the risk of depression. MethodsWe followed 14,908 participants initially free of any history of depression in the “Seguimiento Universidad de Navarra” (SUN) cohort. Information was collected biennially from 1999 to December 2016. We calculated a healthy-lifestyle score (0–10 points), previously associated with cardioprotection, by giving one point to each of the following components: never smoking, physical activity (> 20 METs-h/week), Mediterranean diet adherence (≥ 4 points), healthy body mass index (≤ 22 kg/m2), moderate alcohol consumption (women 0.1–5 g/d; men 0.1–10 g/d of ethanol), avoidance of binge drinking (never more than 5 alcoholic drinks in a row), low television exposure (≤ 2 h/d), short afternoon nap (≤ 30 min/day), time spent with friends (>1 h/d) and working at least 40 h/week. ResultsDuring a median follow-up of 10.4 years, we observed 774 new cases of major depression among participants initially free of depression. The highest category (8–10 factors) showed a significant inverse association with a 32% relative risk reduction for depression compared to the lowest category (0–3 factors) (multivariable-adjusted hazard ratio: 0.68; 95% CI:0.49-0.95) (p for trend = 0.010). ConclusionsAdopting a healthy-lifestyle was associated with a lower risk of incident depression in the SUN cohort. This index, including ten simple healthy lifestyle habits, may be useful for a more integrative approach to depression prevention.

Healthy Lifestyle and Incidence of Metabolic Syndrome in the SUN Cohort.

We assessed the relationship between a healthy lifestyle and the subsequent risk of developing metabolic syndrome. The “Seguimiento Universidad de Navarra” (SUN) Project is a prospective cohort study, focused on nutrition, lifestyle, and chronic diseases. Participants (n = 10,807, mean age 37 years, 67% women) initially free of metabolic syndrome were followed prospectively for a minimum of 6 years. To evaluate healthy lifestyle, nine habits were used to derive a Healthy Lifestyle Score (HLS): Never smoking, moderate to high physical activity (>20 MET-h/week), Mediterranean diet (≥4/8 adherence points), moderate alcohol consumption (women, 0.1–5.0 g/day; men, 0.1–10.0 g/day), low television exposure (<2 h/day), no binge drinking (≤5 alcoholic drinks at any time), taking a short afternoon nap (<30 min/day), meeting up with friends >1 h/day, and working at least 40 h/week. Metabolic syndrome was defined according to the harmonizing definition. The association between the baseline HLS and metabolic syndrome at follow-up was assessed with multivariable-adjusted logistic regressions. During follow-up, we observed 458 (4.24%) new cases of metabolic syndrome. Participants in the highest category of HLS adherence (7–9 points) enjoyed a significantly reduced risk of developing metabolic syndrome compared to those in the lowest category (0–3 points) (adjusted odds ratio (OR) = 0.66, 95% confidence interval (CI) = 0.47–0.93). Higher adherence to the Healthy Lifestyle Score was associated with a lower risk of developing metabolic syndrome. The HLS may be a simple metabolic health promotion tool.

The influence of an afternoon nap on the endurance performance of trained runners

The effectiveness of a nap as a recovery strategy for endurance exercise is unknown and therefore the present study investigated the effect of napping on endurance exercise performance. Eleven trained male runners completed this randomised crossover study. On two occasions, runners completed treadmill running for 30 min at 75% ⩒O2max in the morning, returning that evening to run for 20 min at 60% ⩒O2max, and then to exhaustion at 90% ⩒O2max. On one trial, runners had an afternoon nap approximately 90 min before the evening exercise (NAP) whilst on the other, runners did not (CON). All runners napped (20 ± 10 min), but time to exhaustion (TTE) was not improved in all runners (NAP 596 ± 148 s vs. CON 589 ± 216 s, P = .83). Runners that improved TTE after the nap slept less at night than those that did not improve TTE (night-time sleep 6.4 ± 0.7 h vs. 7.5 ± 0.4 h, P < .01). Furthermore, night-time sleep predicted change in TTE, indicating that runners sleeping least at night improved TTE the most after the nap compared to CON (r2 = −0.76, P = .001). In runners that improved TTE, ratings of perceived exertion (RPE) were lower during the TTE on NAP than CON compared to runners that did not improve (−0.4 ± 0.6 vs. 0 ± 0, P = .05). Reduced exercising sense of effort (RPE) may account for the improved TTE after the nap. In conclusion, a short afternoon nap improves endurance performance in runners that obtain less than 7 h night-time sleep.

Association Between a Healthy Lifestyle Score and the Risk of Cardiovascular Disease in the SUN Cohort

Introduction and objectivesA healthy lifestyle (HLS) is essential to attaining optimal cardiovascular health. Our objective was to assess the association between a HLS score and the incidence of hard cardiovascular disease (CVD) events. MethodsThe SUN project is a dynamic, prospective, multipurpose cohort of Spanish university graduates with a retention proportion of 92%. In 19 336 participants, we calculated a HLS score ranging from 0 to 10 points: never smoking, physical activity (> 20 METs-h/wk), Mediterranean diet adherence (≥ 4/8 points), low body mass index (≤ 22), moderate alcohol intake (women, 0.1-5g/d; men, 0.1-10g/d), low television exposure (≤ 2h/d), no binge drinking (≤ 5 alcoholic drinks anytime), taking a short afternoon nap (< 30min/d), meeting up with friends> 1h/d and working> 40h/wk. ResultsAfter a median follow-up of 10.4 years, we identified 140 incident cases of CVD. After adjustment for potential confounders, the highest category of HLS score adherence (7-10 points) showed a significant 78% relative reduction in the risk of primary CVD compared with the lowest category (0-3 points) (adjusted HR, 0.22; 95%CI, 0.11-0.46). Each healthy habit was individually associated with a lower risk of CVD. ConclusionsA HLS score including several simple healthy habits was associated with a lower risk of developing primary CVD. This index may be useful to reinforce CVD prevention without the need to include traditional risk factors.

Relación entre un índice de estilo de vida saludable y el riesgo de enfermedad cardiovascular en la cohorte SUN

Introduction and objectivesA healthy lifestyle (HLS) is essential to attaining optimal cardiovascular health. Our objective was to assess the association between a HLS score and the incidence of hard cardiovascular disease (CVD) events. MethodsThe SUN project is a dynamic, prospective, multipurpose cohort of Spanish university graduates with a retention proportion of 92%. In 19 336 participants, we calculated a HLS score ranging from 0 to 10 points: never smoking, physical activity (> 20 METs-h/wk), Mediterranean diet adherence (≥ 4/8 points), low body mass index (≤ 22), moderate alcohol intake (women, 0.1-5g/d; men, 0.1-10g/d), low television exposure (≤ 2h/d), no binge drinking (≤ 5 alcoholic drinks anytime), taking a short afternoon nap (< 30min/d), meeting up with friends> 1h/d and working> 40h/wk. ResultsAfter a median follow-up of 10.4 years, we identified 140 incident cases of CVD. After adjustment for potential confounders, the highest category of HLS score adherence (7-10 points) showed a significant 78% relative reduction in the risk of primary CVD compared with the lowest category (0-3 points) (adjusted HR, 0.22; 95%CI, 0.11-0.46). Each healthy habit was individually associated with a lower risk of CVD. ConclusionsA HLS score including several simple healthy habits was associated with a lower risk of developing primary CVD. This index may be useful to reinforce CVD prevention without the need to include traditional risk factors.Full English text available from:www.revespcardiol.org/enFull English text available from:www.revespcardiol.org/en

The effects of short afternoon nap and bright light on task switching performance and error-related negativity

The aim of the present study was to demonstrate the effects of a short nap (20 min) and bright light (>2000 lux) in the afternoon on task switching ability (i.e., switch cost and mixing cost) and error-related negativity (Ne/ERN). The effects of a short nap and bright light on task switching performance have been less reported despite the importance and frequency of task switching as a common activity in many occupational situations. Sixteen volunteers performed a switching task twice a day (1200–1330 h and 1430–21600 h). Participants completed a total of four experimental conditions (control, short nap, bright light, and short nap with bright light). A short nap was taken during the break between the first and second tasks. During the second task, bright light treatment was applied in two of the four conditions. A short afternoon nap improved task-switching performance (i.e., switch cost) and enlarged Ne/ERN amplitude. No effects were found for light conditions on task-switching performance and Ne/ERN amplitude. The results suggest that: (i) a short afternoon nap improves executive functions and self-monitoring that involve the prefrontal cortex; and (ii) the effect of bright light on task-switching performance is smaller compared to a short nap.

Alarm Fatigue Can Decrease the Safety of Dental Office Sedation and Anesthesia

Alarm Fatigue Can Decrease the Safety of Dental Office Sedation and Anesthesia

Can a short nap and bright light function as implicit learning and visual search enhancers?

The present study examined effects of a short nap (20 min) and/or bright light (2000 lux) on visual search and implicit learning in a contextual cueing task. Fifteen participants performed a contextual cueing task twice a day (1200–1330 h and 1430–1600 h) and scored subjective sleepiness before and after a short afternoon nap or a break period. Participants served a total of four experimental conditions (control, short nap, bright light and short nap with bright light). During the second task, bright light treatment (BLT) was applied in the two of the four conditions. Participants performed both tasks in a dimly lit environment except during the light treatment. Results showed that a short nap reduced subjective sleepiness and improved visual search time, but it did not affect implicit learning. Bright light reduced subjective sleepiness. A short nap in the afternoon could be a countermeasure against sleepiness and an enhancer for visual search. Practitioner Summary: The study examined effects of a short afternoon nap (20 min) and/or bright light (2000 lux) on visual search and implicit learning. A short nap is a powerful countermeasure against sleepiness compared to bright light exposure in the afternoon.

The Relationship between Flow, Sleepiness and Cognitive Performance: The Effects of Short Afternoon Nap and Bright Light Exposure

"Flow" is a positive emotional state which typically occurs when a person perceives a balance between the challenges associated with a situation and his or her capabilities to accomplish these demands. While flow often occurs along with positive feelings and high introspective performance, only a few studies have investigated how it is associated with cognitive performance (i.e., objective performance). In the present study, we investigated the relationship between flow, emotions, and cognitive performance. A short nap (20 min) and bright light (>2,000 lux) techniques were used as experimental manipulations to enhance flow. Fifteen participants (31.3 ± 7.19 yr old) took part in four experimental conditions: rest, short nap, bright light, and nap and bright light. Pearson's correlation coefficients were calculated for flow and other indices using standardized data. Results showed that flow scores significantly increased after a short nap and under bright light exposure. The correlations between flow and reaction time were also significant. Flow was significantly associated with positive emotion and sleepiness. These results suggest that a short nap and bright light can be employed as a flow facilitator and that flow status can be used as an indicator in evaluating work efficiency and occupational mental health.

Self-Awakening, Sleep Inertia, and P3 Amplitude in Elderly People

It is well known that sleepiness is sometimes experienced in the afternoon. A short afternoon nap is thought to be effective in reducing sleepiness. However, sleep inertia occurs even after a short nap, and this could be a major risk factor for injuries from falling by the elderly. In the present study, the effect of self-awakening on sleep inertia after a 20-min. nap was examined. Nine participants (M=74.1 yr., SD=5.0 yr.) took part in the three experimental conditions: the self-awakened nap, the forced-awakened nap, and the control (no-nap) conditon. Analysis showed sleepiness and performance after the nap significantly improved compared with the control condition. P3 amplitude tended to be larger after self-awakening than after forced-awakening. The present study indicates a 20-min. nap reduces afternoon sleepiness, and the application of self-awakening may contribute to higher arousal after a nap taken by this elderly group.

Self-Awakening Prevents Acute Rise in Blood Pressure and Heart Rate at the Time of Awakening in Elderly People

Self-awakening, waking up at a designated time decided before sleeping, could prevent failure in the blood circulation vessel system such as heart attack, acute increases in heart rate or blood pressure upon waking. Previous research showed that anticipatory changes occurred in heart rate prior to awakening from a short nap by means of self-awakening for young participants. However, the effects of self-awakening remained unclear for elderly people. The present study examined the effects of self-awakening on heart rate and blood pressure in a short afternoon nap (20 min) among the elderly. Nine participants [74.1 (SD = 5.01) years old] underwent both self-awakening and forced-awakening conditions. In the self-awakening condition, it was revealed that blood pressure gradually increased before the scheduled time of awakening, and that heart rate did not show a rapid increase at arousal. In contrast, forced-awakening induced acute increases in both heart rate and blood pressure. These results suggest that self-awakening facilitates a more smooth transition from sleep to wakefulness via autonomic activation before the time of self-awakening.