Midday Nap Research Articles

Promoting subjective preferences in simple economic choices during nap.

Sleep is known to benefit consolidation of memories, especially those of motivational relevance. Yet, it remains largely unknown the extent to which sleep influences reward-associated behavior, in particular, whether and how sleep modulates reward evaluation that critically underlies value-based decisions. Here, we show that neural processing during sleep can selectively bias preferences in simple economic choices when the sleeper is stimulated by covert, reward-associated cues. Specifically, presenting the spoken name of a familiar, valued snack item during midday nap significantly improves the preference for that item relative to items not externally cued. The cueing-specific preference enhancement is sleep-dependent and can be predicted by cue-induced neurophysiological signals at the subject and item level. Computational modeling further suggests that sleep cueing accelerates evidence accumulation for cued options during the post-sleep choice process in a manner consistent with the preference shift. These findings suggest that neurocognitive processing during sleep contributes to the fine-tuning of subjective preferences in a flexible, selective manner.

Sleep extension reduces pain sensitivity

IntroductionInsufficient sleep increases pain sensitivity in healthy individuals. Additionally, extending sleep (eg, increasing nocturnal sleep time or adding a mid-day nap) has been shown to restore pain sensitivity to baseline levels in sleep deprived/restricted individuals. Whether sleep extension can reduce pain sensitivity beyond baseline levels in non-sleep restricted/deprived individuals remains unknown. MethodsIn a sample of 27 healthy, pain-free, normally-sleeping individuals (17 males, mean age ∼24 yrs), we examined the impact of five nights of sleep extension on pain sensitivity. Pain threshold (elapsed time until the participant reported pain) and pain tolerance (total time the participant kept the hand submerged in the cold water) were measured using the Cold Pressor Task. Furthermore, we assessed the extent to which self-reported sleep amount in relation to the minimal subjective sleep requirement for adequate performance (sleep credit) was associated with pain sensitivity changes. ResultsOn average individuals slept almost 2 extra hours per night. Our results indicate that sleep extension increases pain tolerance beyond baseline levels. However, sleep extension did not impact pain threshold. We also found that individuals with a smaller sleep credit (ie, those who habitually obtain less sleep than they feel they need) experienced greater increases in pain tolerance after extending sleep. ConclusionsThe present findings suggest that sleep extension may increase pain tolerance but not pain threshold in healthy individuals who normally sleep the recommended amount. Our findings also support the idea that sleep credit may be a strong indicator of sleep debt in the context of pain sensitivity.

Naps Do Not Change Delay Discounting Behavior in Young Adults.

When offered a choice of $40 today or $50 later, many would choose the immediate reward over the greater delayed reward. Such behavior is a result of future gains being discounted such that their value is rendered less than that of the immediate gain. Extreme discounting behaviors are associated with impulsivity and addiction. Given recent evidence of sleep’s role in decision making, we tested the hypothesis that sleep would reduce delayed discounting behavior. Twenty young adults (M = 20.19 years, SD = 0.98 years; 6 males) performed a hypothetical delay discounting task, making a series of choices between an immediate reward (from $0 to $50) or a larger reward ($50) available at a delay of 2, 4, 8, 14, or 22 weeks. Participants performed the task before and after a mid-day nap, and before and after an equivalent interval of wake (within subject, order counterbalanced, wake, and sleep conditions separated by 1 week). As expected, indifference points decreased with longer delays both prior to and following the nap/wake interval. However, the impact of a nap interval on discounting did not differ from the impact of a wake interval. Thus, while sleep has been shown to play an active role in some financial decision-making tasks, a nap is not sufficient to change delay discounting behavior.

Association between nighttime sleep duration, midday naps, and glycemic levels in Japanese patients with type 2 diabetes

ObjectivesTo clarify the relationship between nighttime sleep duration, midday naps, and glycemic control in Japanese patients diagnosed with type 2 diabetes (n = 355) or impaired glucose tolerance (n = 43). MethodsA total of 398 patients completed a self-administered questionnaire on sleep duration/quality and were divided into five groups according to their self-reported nighttime sleep duration: <5 h, 5–6 h, 6–7 h, 7–8 h, and >8 h. Each group was further divided into two subgroups each according to the presence or absence of midday naps. Poor glycemic control was defined as HbA1c ≥ 7.0%. ResultsShort nighttime sleep (<5 h), poor sleep induction, daytime sleepiness, and low sleep satisfaction were associated with high HbA1c levels. HbA1c was higher in the short nighttime sleep/no nap group than in non-nappers with different nighttime sleep duration, whereas the short nighttime sleep/nap group showed similar HbA1c levels to the other nap subgroups. In multivariate logistic regression models, after adjusting for a number of potential confounders, short (<5 h) nighttime sleep without nap was significantly associated with poor glycemic control compared with 6–7 h nighttime sleep without nap (OR [95% CI]: 7.14 [2.20–23.20]). However, taking naps reduced this risk for poor glycemic control in short sleepers. Other risk factors for poor glycemic control were low sleep satisfaction (1.73 [1.10–2.70]) and poor sleep induction (1.69 [1.14–2.50]). ConclusionsPoor sleep quality and quantity could aggravate glycemic control in type 2 diabetes. Midday naps could mitigate the deleterious effects of short nighttime sleep on glycemic control. Clinical trials registrationUMIN 000017887.

Effects of a short midday nap on habitual nappers' alertness, mood and mental performance across cognitive domains.

This study examines whether the benefits of a short midday nap on habitual nappers' mental performance depend on the cognitive domain and the task difficulty. Eighteen healthy college students with the long-term habit of a midday nap (13:00-14:00hours) participated in a nap-deprivation study. On two separate days with at least 3days in between, participants either took a nap or remained awake, and were subsequently tested on a simple sustained attention task (Psychomotor Vigilance Test), two more complex attention tasks (Go/No-Go and Flanker task) and one working memory task (2-back). For each task, an easy and a difficult version were administered. The time course of subjective sleepiness and mood were also measured in both napping conditions. The results revealed that short midday nap deprivation significantly impaired participants' performance on both the easy and difficult versions of the Psychomotor Vigilance Test task, as well as accuracy but not reaction speed in the Go/No-Go task. Accuracy in the difficult version of the Flanker task and the 2-back task was also lower in the no-nap condition, while reaction speed in the 2-back task but not the Flanker task was reduced without a nap in both the easy and difficult versions. Moreover, subjective sleepiness was significantly increased after nap deprivation, but moods remained unaffected in the no-nap condition. These findings contribute to current research suggesting that effects of a midday nap on task performance depend on the cognitive domain as well as task difficulty. Our study highlights the importance of considering task characteristics to evaluate the benefits of a regular midday nap in practical working life.

Salivary Cortisol Levels Predict Therapeutic Response to a Sleep-Promoting Method in Children with Postural Tachycardia Syndrome

To determine the value of salivary cortisol concentrations in predicting the efficacy of sleep-promoting treatment in children with postural tachycardia syndrome (POTS). This prospective study involved 40 children with POTS and 20 healthy children (controls). POTS was diagnosed using the head-up or head-up tilt test. Patients with POTS received a sleep-promoting treatment: >8 hours of sleep every night and a midday nap in an appropriate environment; no drinking water or exercising before bedtime; and urination before bedtime. The Pittsburgh Sleep Quality Index was used to evaluate sleep quality, and symptom scores were used to assess POTS severity. Salivary samples were collected upon awakening, 30 minutes after awakening, at 12:00 p.m., 4:00 p.m., and 8:00 p.m., and at bedtime before treatment. Enzyme-linked immunosorbent assay was used to measure salivary cortisol concentrations. Cortisol concentrations were significantly higher in patients with POTS than in the controls at all time points (P < .05 for all). PSQI scores were significantly higher in patients with POTS (7.2 ± 3.0) than in the controls (1.35 ± 1.39; t = -10.370, P <.001). Salivary cortisol concentrations at awakening were significantly higher in responders than in nonresponders (4.83 ± 0.73 vs 4.05 ± 0.79 ng/mL, t = -3.197, P = .003). The area under the receiver operating characteristic curve was 75.8%, (95% CI 59.3%-92%). Cut-off at-awakening salivary cortisol concentrations of >4.1 ng/mL yielded 83.3% sensitivity and 68.7% specificity in predicting therapeutic efficacy. At-awakening salivary cortisol concentrations may predict the efficacy of sleep-promoting treatment in patients with POTS.

Sleeping Disorders among Medical Students in Saudi Arabia in Relation to Anti-Insomnia Medications

Background: due to their demanding lifestyle, sleep deprivation is common amongst the medical students. A study, which followed 1,007 young adults at a health maintenance organization for 3.5 years, found that a history of insomnia predicted new-onset depression, also other psychiatric disorders. Another study showed that sleeping disorders and insomnia are negatively associated with academic performance in medical students in Saudi Arabia. The relationship between sleeping disorders among medical students in Saudi Arabia; about anti-insomnia medications is insufficiently addressed in the literature. This study aimed to assess the relationship between sleep habits and sleep duration with academic performance in the medical students. Objectives: this study aimed to determine sleep pattern disorders among medical students, as well as, the use of anti-insomnia medications and alsoto define the relation regarding the academic performance among the sample medical students in Saudi Arabia. Methods: this is a cross-sectional study which was conducted among the medical students at three different medical schools, Riyadh, Saudi Arabia from May 2014 to December 2014.. A self-administrated randomized questionnaire was developed and designed in the Arabic language in the form of multiple choices and short answers, concerning age, gender, educational level, grade point average GPA, financial status, total sleep hours per day, mid-day naps duration, quality and latency of sleep and using of anti-insomnia medications. Epworth Sleepiness Scale (ESS) was also involved in the questionnaire. Results: out of 276 received questionnaires, 237 questionnaires were completed. Out of those 237 subjects, 92 subjects were female students (38.7%), and 145 were male students (60.9%). The mean age was 22 ±2.37. Regarding GPA, 122 participants got below average GPA, 28 participants got average GPA, 62 participants got an average GPA, while 25 participants got an excellent GPA (51.3%, 11.8%, 26.1%,10.5% respectively). 127 of the participants were used medications to help them to sleep, and 9.7% used it occasionally, whereas 110 of the participants did not use any medication. Out of 127 participants who used the medications, 92.5% of them agreed that medications they took were helpful and effective.Conclusion: this study showed a significant relationship between the use of anti-insomnia medications and the academic performance of medical students, further committee and education should be established by the universities and faculties to enhance the student’s awareness to the issue of the chronic use of anti-insomnia medications at first and to apply a perfectly healthy environment with less stress and condensed classes and exams.

Sleep quality is associated with weight loss maintenance status: the MedWeight study

Sleep duration and quality have been associated with many health outcomes, including weight management. We aimed to investigate the effect of self-reported sleep duration and quality on weight loss maintenance in participants of the MedWeight study, a registry of individuals that lost at least 10% of body weight in the past and either maintained the loss (maintainers: weight maintenance of at least 10% of initial weight loss) or regained it (regainers: weight ≥95% of their maximum body weight). Study participants included 528 volunteers (61% women). Sleep quantity referred to the reported duration of nocturnal sleep, as well as the frequency of mid-day naps during the last month. Sleep quality was assessed through the Athens Insomnia Scale (AIS). Reported sleep quantity was associated with weight maintenance status, but the association became non-significant when the AIS score entered the model. In specific, AIS was inversely associated with the likelihood of being a maintainer (OR=0.89 per AIS unit, 95% CI: 0.81 – 0.98), even after adjusting for potential confounders. Sex-specific analysis revealed that the association between the AIS score and maintenance status was evident in men but not in women. Future studies are needed to confirm these results in other population groups and reveal underlying mechanisms.

A "healthy diet-optimal sleep" lifestyle pattern is inversely associated with liver stiffness and insulin resistance in patients with nonalcoholic fatty liver disease.

Several lifestyle habits have been described as risk factors for nonalcoholic fatty liver disease (NAFLD). Given that both healthy and unhealthy habits tend to cluster, the aim of this study was to identify lifestyle patterns and explore their potential associations with clinical characteristics of individuals with NAFLD. One hundred and thirty-six consecutive patients with ultrasound-proven NAFLD were included. Diet and physical activity level were assessed through appropriate questionnaires. Habitual night sleep hours and duration of midday naps were recorded. Optimal sleep duration was defined as sleep hours ≥ 7 and ≤ 9 h/day. Lifestyle patterns were identified using principal component analysis. Eight components were derived explaining 67% of total variation of lifestyle characteristics. Lifestyle pattern 3, namely high consumption of low-fat dairy products, vegetables, fish, and optimal sleep duration was negatively associated with insulin resistance (β = -1.66, P = 0.008) and liver stiffness (β = -1.62, P = 0.05) after controlling for age, sex, body mass index, energy intake, smoking habits, adiponectin, and tumor necrosis factor-α. Lifestyle pattern 1, namely high consumption of full-fat dairy products, refined cereals, potatoes, red meat, and high television viewing time was positively associated with insulin resistance (β = 1.66, P = 0.005), although this association was weakened after adjusting for adiponectin and tumor necrosis factor-α. A "healthy diet-optimal sleep" lifestyle pattern was beneficially associated with insulin resistance and liver stiffness in NAFLD patients independent of body weight status and energy intake.

EP 118. Can midday naps boost learning in older adults?

Naps as well as a night of sleep were found to improve motor learning in young individuals (Doyon et al., 2009). The capacity of older adults to learn and stabilize motor memory traces (consolidation) during over-night sleep is limited (Pan and Rickard, 2015, Backhaus et al., 2015). However a small number of studies suggested sleep-dependent consolidation in healthy older adults, immediately after sleep (Gudberg et al., 2015, Al-Sharman and Siengsukon, 2014) or after a delayed period (Tucker et al., 2011, Korman et al., 2015). Can midday naps enhance motor learning in older adults? We evaluated the performance changes of a sample of thirty-three healthy older adults (60–82 years) by implementing a napping paradigm in a motor learning setup (sequence learning and motor adaption). The participants were randomly assigned to one of three groups; short nap group (a forty-five minutes nap opportunity, 10–20 min sleep), long nap group (ninety minutes nap opportunity, 50–80 min sleep) or a forty-five minutes period of wakefulness. Three learning sessions on two consecutive days were compared for both tasks with the repeated measures mixed model approach. All older adults were able to improve their task performance in both tasks throughout all sessions. For sequence learning no differences between the nap groups could be found following the midday nap, nor after an extended period of consolidation, i.e. the following day. Similarly no significant differences between the groups could be found directly after the midday break when performing the motor adaptation task. However during the final block of the last session nappers performed significantly better (p = 0.023) than those adults staying awake. Although midday naps may have a great recuperative value (Tamaki et al., 1999, Campbell et al., 2011), these effects could not be projected on motor learning and subsequent motor performance directly after napping. Based on the current results we conclude that short daytime naps do not enhance the effects of motor learning and consolidation. Thus, deficits in consolidation apparent in older adults are not dependent of the duration of sleep but rather of the process of consolidation during sleep, which seems to be impaired in older adults. This work was supported by the Stiftung der Deutschen Wirtschaft providing a PhD Scholarship to W.B. W.B and F.C.H. hold a research grant from the Werner-Otto-Foundation (9/87).

Napping reduces emotional attention bias during early childhood.

Sleep loss alters processing of emotional stimuli in preschool-aged children. However, the mechanism by which sleep modifies emotional processing in early childhood is unknown. We tested the hypothesis that a nap, compared to an equivalent time spent awake, reduces biases in attention allocation to affective information. Children (n=43; M=55.40months, SD=8.05months) completed a Dot Probe task, which provides a measure of attention biases to emotional stimuli, following a mid-day nap and an equivalent interval spent awake. No emotional attention biases emerged when children napped. However, when nap-deprived, children exhibited biases towards negative and positive stimuli. This emotional bias after wake was greater in children who napped habitually. Gender differences also emerged such that females were more attentive to positive emotional stimuli whereas males showed heightened attention to negative emotional stimuli, regardless of having napped or not. Moreover, greater slow wave activity (SWA) during the nap was associated with faster responding, which suggests that SWA may promote efficiency of attention allocation. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=JIoZ8mzxQgg.

Motor Performance Is not Enhanced by Daytime Naps in Older Adults

The impact of sleep on motor learning in the aging brain was investigated using an experimental diurnal nap setup. As the brain ages several components of learning as well as motor performance change. In addition, aging is also related to sleep architectural changes. This combination of slowed learning processes and impaired sleep behavior raises the question of whether sleep can enhance learning and specifically performance of procedural tasks in healthy, older adults. Previous research was able to show sleep-dependent consolidation overnight for numerous tasks in young adults. Some of these study findings can also be replicated for older adults. This study aims to clarify whether sleep-dependent consolidation can also be found during shorter periods of diurnal sleep. The impact of midday naps on motor consolidation was analyzed by comparing procedural learning using a sequence and a motor adaptation task, in a crossover fashion in healthy, non-sleep deprived, older adults randomly subjected to wake (45 min), short nap (10–20 min sleep) or long nap (50–70 min sleep) conditions. Older adults exhibited learning gains, these were not found to be sleep-dependent in either task. The results suggest that daytime naps do not have an impact on performance and motor learning in an aging population.

Daytime sleep has no effect on the time course of motor sequence and visuomotor adaptation learning

Sleep has previously been claimed to be essential for the continued learning processes of declarative information as well as procedural learning. This study was conducted to examine the importance of sleep, especially the effects of midday naps, on motor sequence and visuomotor adaptation learning. Thirty-five (27 females) healthy, young adults aged between 18 and 30years of age participated in the current study. Addressing potential differences in explicit sequence and motor adaptation learning participants were asked to learn both, a nine-element explicit sequence and a motor adaptation task, in a crossover fashion on two consecutive days. Both tasks were performed with their non-dominant left hand. Prior to learning, each participant was randomized to one of three interventions; (1) power nap: 10–20min sleep, (2) long nap: 50–80min sleep or (3) a 45-min wake-condition. Performance of the motor learning task took place prior to and after a midday rest period, as well as after a night of sleep. Both sleep conditions were dominated by Stage N2 sleep with embedded sleep spindles, which have been described to be associated with enhancement of motor performance. Significant performance changes were observed in both tasks across all interventions (sleep and wake) confirming that learning took place. In the present setup, the magnitude of motor learning was not sleep-dependent in young adults – no differences between the intervention groups (short nap, long nap, no nap) could be found. The effect of the following night of sleep was not influenced by the previous midday rest or sleep period. This finding may be related to the selectiveness of the human brain enhancing especially memory being thought of as important in the future. Previous findings on motor learning enhancing effects of sleep, especially of daytime sleep, are challenged.

Napping to modulate frustration and impulsivity: A pilot study

Recent research has shown that napping can increase positive mood, and improve immune functioning, demonstrating the additional benefits of naps beyond reducing sleepiness and fatigue. Because prolonged wakefulness is becoming more common, it is becoming increasingly important to identify effective approaches to decrease resultant cognitive deficiencies. The present study aimed to examine the impact of a brief, midday nap on an aspect of executive functioning, emotional control. 40 subjects were randomized into a nap or no-nap condition, and emotional control was measured with a self-report impulsivity measure and frustration tolerance task. Results revealed that nappers showed a decrease in self-reported impulsivity and increased tolerance for frustration, while those in the no-nap condition showed the opposite pattern. These results indicate that emotional control may become impaired from wakefulness that builds across the day, and that napping may be an effective countermeasure.

Naps show no enhancing effects on movement performance in healthy young adults

Background: Sleep has previously been found to be essential in the continued learning processes of declarative information, such as word-pairs. To examine the importance of sleep, especially the effects of midday naps, on motor learning, this randomized trial was conducted. Purpose: This trial is part of a larger study evaluating the effect of sleep intervention involving midday-naps on movement performance and learning, in relation to an equivalent period of wakefulness, in various populations. This research will provide a basis for future sleep-related developments of health care plans, especially concerning people with chronic disability, such as stroke. Methods: The study was approved by the ethics committee Hamburg and each participant provided informed consent prior to the study. 35 healthy, right-handed, young adults participated (18–30yrs), learningboth a 9-element sequence task (SE) and a motor adaptation (MA) task in a crossover fashion on two consecutive days. Both tasks were performed with the left hand. Prior to learning, each subject was randomized to one of three conditions;

Improving sleep and cognition by hypnotic suggestion in the elderly

Sleep quality markedly declines across the human lifespan. Particularly the amount of slow-wave sleep (SWS) decreases with age and this decrease is paralleled by a loss of cognitive functioning in the elderly. Here we show in healthy elderly females that the amount of SWS can be extended by a hypnotic suggestion “to sleep deeper” before sleep. In a placebo-controlled cross-over design, participants listened to hypnotic suggestions or a control tape before a midday nap while high density electroencephalography was recorded. After the hypnotic suggestion, we observed a 57% increase in SWS in females suggestible to hypnosis as compared to the control condition. Furthermore, left frontal slow-wave activity (SWA), characteristic for SWS, was significantly increased, followed by a significant improvement in prefrontal cognitive functioning after sleep. Our results suggest that hypnotic suggestions might be a successful alternative for widely-used sleep-enhancing medication to extend SWS and improve cognition in the elderly.

The effects of midday nap duration on the risk of hypertension in a middle-aged and older Chinese population: a preliminary evidence from the Tongji-Dongfeng Cohort Study, China.

Evidence from epidemiological studies suggested that shorter and longer duration of nocturnal sleeping may increase the risk of hypertension for older adults. Little is known about the duration of midday nap on the variability of blood pressure among older adults. In this study, we examined whether duration of habitual midday nap is associated with level of blood pressure or the risk of hypertension in a middle-aged and older Chinese population. A total of 27 009 participants (mean age 63.6 years) from Dongfeng-Tongji Cohort Study received baseline examination including physical examination and laboratory tests, and a face-to-face-interview including demographic information, disease history, and lifestyle. Participants were categorized into five groups according to nap duration, such as no napping, less than 30 min, 30∼60 min, 60∼90 min, and at least 90 min. A series of categorical logistic regression models was used to examine the odd ratios of nap duration with hypertension. The level of SBP and DBP increased significantly with longer duration of habitual midday napping. Nappers with longer nap duration had considerably higher rate of hypertension. The longer duration of napping was related to higher blood pressure level and was associated with a higher risk of hypertension. After adjusting for possible confounders, the longer duration (>60 min) of napping was still associated with hypertension : Our findings showed that the practice of longer afternoon nap is associated with a higher increased risk of hypertension, independent of several covariates. Further prospective researches are needed to examine the midday nap duration for development of hypertension.

Exposure to low environmental radiation and longevity. Insights from the Ikaria Study

Ikaria, a medium-size island consisting mainly of igneous rocks, in central eastern Aegean Sea, Greece, has recently joined the “Blue Zones”, a part of a large anthropologic project of the Quest Network, Inc. funded by the National Institute on Aging and the National Geographic [1], as the percent of people over 90+ years was almost 10-fold than the European average. Following this observation, the Ikaria Study was conducted in 2009, to further explore the secrets of the long-livers. In a recent report from the study, it was suggested that consumption of a Mediterranean-type of diet, all-day enrollment to any type of physical activities, smoking cessation, mid-day naps, might depict some of the “secrets” of the long-livers [2].

Sleep spindles in midday naps enhance learning in preschool children

Despite the fact that midday naps are characteristic of early childhood, very little is understood about the structure and function of these sleep bouts. Given that sleep benefits memory in young adults, it is possible that naps serve a similar function for young children. However, children transition from biphasic to monophasic sleep patterns in early childhood, eliminating the nap from their daily sleep schedule. As such, naps may contain mostly light sleep stages and serve little function for learning and memory during this transitional age. Lacking scientific understanding of the function of naps in early childhood, policy makers may eliminate preschool classroom nap opportunities due to increasing curriculum demands. Here we show evidence that classroom naps support learning in preschool children by enhancing memories acquired earlier in the day compared with equivalent intervals spent awake. This nap benefit is greatest for children who nap habitually, regardless of age. Performance losses when nap-deprived are not recovered during subsequent overnight sleep. Physiological recordings of naps support a role of sleep spindles in memory performance. These results suggest that distributed sleep is critical in early learning; when short-term memory stores are limited, memory consolidation must take place frequently.

Midday naps and the risk of coronary artery disease: results of the Heinz Nixdorf Recall Study.

Several studies have assessed the association between midday nap and cardiovascular outcomes and reported heterogenous results. Concern exists that confounding might have distorted these results and contributed to discrepancies among them. This study prospectively examines the association between midday nap habits and the occurrence of coronary artery disease in a non-Mediterranean population. The baseline examination of 4,123 participants aged 45-75 years. Measurements included interviews, physical examinations, laboratory tests, and electron beam computed tomography. We studied the influence of midday nap habits on risk of coronary artery disease. We adjusted for several potential confounders including measures of subclinical atherosclerosis-such as coronary calcium score and ankle brachial index-at baseline. Cardiac events during a median follow-up of 8.1 years were defined as nonfatal myocardial infarction and sudden cardiac death. Overall, 135 of 4,123 subjects (3.3%) either suffered from acute myocardial infarction (81 subjects) or died due to a sudden cardiac death (54 subjects) during follow-up. After adjustment for several confounders including measures of subclinical atherosclerosis, regular long (> 60 min) midday nap was associated with an increased hazard ratio of cardiac events (hazard ratio 2.12, 95% confidence interval 1.11-4.05). As our detailed confounder analyses showed, confounding is not the sole explanation for this finding. Future research on midday naps should focus on biological mechanisms that may be responsible for increasing the risk of coronary artery disease among subjects taking regular long midday naps.