Our findings indicate that 32% of our study participants napped regardless of whether or not they had asthma. This finding is striking given the National Sleep Foundation’s Sleep in America Poll results that reported only 2% of 6 year old children napped daily and that children who got the age recommended amount of nighttime sleep were the least likely to nap26
. The nap percentages we found are also higher than previous reports that 1 to 14% in school-aged children nap32, 33
. Our percentages are higher than previously reported which may have been influenced by our recruitment strategies. Parents concerned about their child’s sleep may have chosen to participate in greater numbers than those with fewer sleep concerns. Their children may indeed have had more problematic sleep and thus napped more then a representative sample of all children with and without asthma. Future research with children of these ages, where sleep is only one of many recruitment foci, could help determine if the high percentage of napping we found is more prevalent today than in the past or was largely influenced by our recruitment procedures.
In our study the average nighttime sleep duration measured objectively via actigraphy was 7.52 hours (7.29 hr and 7.75 hr for nappers and non nappers respectively). This is much less than the parent reported mean of 9.4 hours in the Sleep in America Poll for 1st
graders and the 10–11 hours recommended by experts on the Sleep of American Children web site. The mean bedtime (sleep onset) in our study was near 11pm for nappers. This contrasts with the mean of 9pm for school age children in the 2004 Sleep in America Poll26
. Our high rate of napping may be related to the study children’s inadequate nighttime sleep, asthma, and variability in sleep onset times.
In our study, nappers were more likely to be diagnosed with asthma. Indeed 44% of the children with asthma self-reported daytime naps in their diary. Average nighttime sleep duration between children with asthma and without asthma via actigraphy did not differ however. Physiologic demands of asthma with unrecognized nighttime symptoms, or the fact that perhaps children with asthma require more sleep than their non-asthma peers may be responsible for this combination of findings. A recent study found that parents of children with asthma report less satisfaction with their child’s sleep than do parents of children without asthma34
. Additional research is warranted on sleep patterns and nighttime symptoms in children with chronic illnesses, especially asthma. Whether subtle respiratory symptoms in children with asthma influence nighttime sleep and drive for daytime naps requires further investigation. Symptoms common in asthma (wheeze and chronic cough) have been associated with difficulty falling asleep, restless sleep, and daytime sleepiness35
. The specific etiologies of the differential sleep characteristics between children with and without asthma must be identified to develop effective interventions in the children with asthma.
Total nighttime sleep as measured by actigraphy was shorter for nappers than non-nappers. Rise times (sleep offset times) seen in this study were likely due to school start times, since the majority of children in our study participated during the school year, Sunday through Thursday night. In our study, nappers had more variability in their bed times/sleep onset (30 minutes) but not their rise times. Daytime napping may compensate for insufficient nighttime sleep however; this may be impractical when school, social or athletic activities prevent adequate daytime rest periods. A recent study found that a 30 minute extension of sleep or an hour restriction impacted healthy children’s neurocognitive function the following day36
. A 30 minute extension was associated with improvements in memory, sustained attention, and behavioral inhibition tasks. Additional research is warranted to determine the impact of sleep extension and restriction in healthy children and in those with chronic illness. If a 20–30 minute difference in nighttime sleep as seen in our study lead children to nap, could an in-home intervention to extend sleep by this amount provide beneficial effects and alleviate the need for daytime napping for children. Parents, counselors and health care providers may believe it too difficult to enact behavior changes that require large increases in nighttime sleep but may be willing to attempt interventions targeting a 20–30 minute extension if they felt it would bring improvements for the child’s health and functioning. If such extensions brought desired outcomes, families might then be motivated to make further improvements in the child’s sleep until the recommended amount of sleep is obtained on a regular basis.
If daytime napping is indeed an indication of the need for more nighttime sleep, attention needs to be given children who report naps even if they do not concurrently report morning tiredness, sleepiness or overall poor sleep quality. We found such morning self reports did not differ by nap status and others have found only modest correlations as well37
. Self-report may be insensitive to the subtle need to supplement inadequate nighttime sleep in most children, particularly when self report is obtained upon awakening in the morning. In addition, sleepiness, tiredness, and alertness are subjective states and what is ‘typical’ for the child may soon become ‘normal’ for the child and not be perceived by them as worthy of special comment. Indeed, the more slowly and chronic the perception, the less likely the child may be to report it as unusual. Relying on the child to complain of morning sleepiness/tiredness to initiate a more formal assessment of sleep thus appears inadequate. Parent or child report of napping however should always trigger assessment. Future research should examine the extent to which self-report of napping actually captures even brief naps children may take while watching TV, videos, or studying by verifying them with daytime actigraphy analysis.
Objective assessment of sleep onset and offset is necessary since we found neither parent nor child diary report of bedtime the same as time of sleep onset determined by actigraphy for most children. Objective measures should also be used to monitor improvements in sleep when interventions are implemented so reporting bias is minimized. We found actigraphy as an objective assessment tool to be acceptable to all children and parents in the study. Although children did at times forget to return the actigraphy to their wrist after bathing or swimming, the vast majority provided complete data. Children reported showing off their ‘wrist computer’ to peers and none reported feeling stigmatized by wearing it. If an underlying physiologic concern is suspected to cause inadequate sleep, a sleep specialist should be consulted to determine if a sleep laboratory polysomnographic objective assessment is advisable, either immediately or subsequent to actigraphy evaluation. Future polysomnographic research with children is also needed to determine if/how daytime napping in school age children alters nighttime sleep architecture since little is known in this area.
Similar to others, we found racial differences between minority and Caucasian children in time of sleep onset and trends in total sleep duration as well as variability of sleep duration and sleep offset, all with minority children showing disadvantage. Goodwin and colleagues found that young Hispanic children napped more frequently than young Caucasian children; however by age 9–11 these differences were no longer true33
. In addition, total night sleep time was less for these Hispanic children regardless of age which could suggest that daytime sleep was supplementing insufficient nighttime sleep. A recent report by Adam and colleagues found that Hispanic children also slept less on weekends38
. Sleep duration was associated with the child’s amount of television, computer and video game use, sports, and religious and social activities. Shorter nighttime sleep durations extending to the weekend continue any negative influences of inadequate weekday sleep, possibly contributing to academic disparities.
Evidence-based early interventions to improve children’s sleep are needed. Child health practitioners report that they feel ill equipped for this type of life style counseling and they want more clinical research in the area39
. Books are written to directly help parents of young children but less is available for the parents of school age children and the children themselves. The National Sleep Foundation web site provides brief materials to increase knowledge of the sleep needs of school age children however, improving family knowledge alone will probably be inadequate to generate and sustain the needed behavior change necessary for most youth. Cognitive behavioral approaches implemented by counselors or health practitioners using age appropriate motivational interviewing strategies with both parent and child might prove effective to resolve behavior related sleep problems before they become entrenched or resistant to brief interventions. Much more research is needed in the area to test effectiveness of theoretically sound strategies since evidence found in the current study continues to suggest American school age children are not getting adequate nighttime sleep.
There are several limitations to this study. First, the age range of children was limited to 9–11 years so, findings are not necessarily applicable to older or younger children. We studied only non-chronically ill children and those with asthma and possible concurrent allergies therefore, the extent to which findings can be generalized to children having additional chronic illnesses is unknown. We were particularly interested in weekdays when the children’s napping would be constrained by school starts and additional research protocols prohibited us from gathering data of the subsequent weekend nights’ sleep. Thus we do not know the stability of the children’s sleep patterns or the impact of the prior week’s sleep on weekend night and daytime sleep. Wording of recruitment fliers may have attracted parents whose children indeed had more sleep issues than typical 9-to −11 year old children and unexamined variables including the child’s prior night’s sleep architecture, home sleeping environment, cultural practices, family race, ethnicity, education and socio-economic status should be investigated for their potential influence on napping. Lastly, the child’s report of napping was self-report vs. actigraphy verified and without a day and time-stamp we are unable to verify that the children actually recorded twice a day to reduce recall problems. With improved digital diary equipment this limitation might be eliminated in future research.
In summary, we found napping to be a more common behavior in school age children then anticipated. Children with asthma and those of minority status were disproportionately represented in the napping group. Children self-reporting napping had evidence of later and more variable bedtimes, and they obtained less sleep than advisable for their age. Although napping may be a compensatory behavior for children with inadequate nighttime sleep, it is likely not available to the child when most needed; weekdays during the school year. Much more needs to be learned about sleep in school age children with and without chronic illnesses but, for now, the design and testing of effective strategies to reduce variability and increase duration of nighttime sleep in school age child who nap seems paramount.