Preschoolers' Sleep: Current U.S. Community Data within a Historical and Sociocultural Context
Keefe-Cooperman, Kathleen, Brady-Amoon, Peggy, Journal of Early Childhood and Infant Psychology
Sleep is a critically important yet understudied phenomenon in psychology and education. Parents and others often talk about preschoolers' sleep. They express concerns ranging from how much sleep is appropriate to difficulties with night awakenings. Many a visit with the pediatrician involves a discussion about sleep patterns. However, suggestions offered by clinicians, grandparents, and family friends are often based on personal experience or generally accepted yet unexamined and unsupported guidelines (US Department of Health and Human Services; HHS, 2003). Despite the attention given to sleep disorders in the medical and medically-related literature, little is known about normal human sleep (HHS, 2003) including typically-developing preschool children's sleep patterns (Bates, Viken, Alexander, Beyers, & Stockton, 2002).
Sleep accounts for 40% of the daily life of children and adolescents (Mindell & Owens, 2003) and is central to the preschool child's development and growth (HHS, 2003). More specifically, sleep is associated with preschoolers' behavior and cognitive readiness for learning (Bates et al., 2002). A more regular sleep schedule is also associated with preschool adjustment. Children with a regular sleep schedule adjust better to preschool than their peers with more disrupted sleep patterns (Bates et al., 2002). Regular and earlier bedtimes are also associated with fewer behavioral difficulties (Hale, Berger, LeBourgeois, & Brooks-Gunn, 2010). Conversely, less sleep at night and during a 24 hour period has been linked with a higher number of externalizing behavior problems such as defiance (Lavigne et al., 1999). Consistent with this line of inquiry, a regular bedtime was found to be the greatest predictor of a developmentally appropriate outcome at age 4, with less hyperactivity, inattention, and impulsivity manifested (Gaylor, 2010). For all of these reasons, sleep is an important area for psychologists to consider.
Although the National Sleep Foundation (NSF, 2011) recommends preschoolers get between 11-13 hours of sleep per night, there is no evidence to show this has been or continues to be normative or optimal in any setting. Overall, despite its limitations, sleep research shows wide variation in preschoolers' normative sleep patterns, some of which are associated with demographic differences (Hale et al., 2009; HHS, 2003).
Preschool children's sleep patterns are important to study given their association with daily behaviors, adjustment, and learning (Bates et al. 2002; Hale et al., 2009; Lavigne et al., 1999). In addition to filling a much needed gap, the study of sleep patterns has the potential to contribute to the school readiness, early identification of developmental concerns, and an intervention knowledge-base. Furthermore, the identification of current sleep patterns for a typically- developing sample would provide additional evidence about current sleep guidelines (NSF, 2011) and foundational biological aspects of normative functioning. Third, given the long, intermittent interest in sleep research (Matricciani, Olds, & Petkov, 2011), we posited that looking at current data within a historical context would provide information about preschool children's sleep patterns over time. The next section offers a review of published research focused on preschoolers' sleep over the last century.
The Historical Context of Sleep
The first known large-scale observational studies of preschooler sleep were published primarily by women in the 1920s (Chant & Blatz, 1928; Flemming, 1925; Foster, Goodenough, & Anderson, 1928). For example, Flemming discovered the recommended but unnamed schedules for sleep provided by pediatricians and child-care specialists to be vastly different than her findings. Experts recommended sleep allotments for 3-4 year olds of 12-14 hours per night as reported by Foster et al. (1928). Taken together, these early studies found that preschoolers slept an hour or two less, on average, than the then-popular recommendations of self-proclaimed authorities (Healy, 1972). This finding was confirmed by Jenni and O'Connor (2005) who reported that early 20th century studies indicated children did not get enough sleep based on 19th century recommendations. Overall, these studies used parent/guardian reports of children's typical bedtimes and wake times to calculate children's average nightly and sometimes day time sleep.
It is interesting to note that many historical studies of preschooler sleep interpreted data according to the predominant theoretical foci of the time. For instance, early researchers considered children's sleep in relation to whether a window was open in the bedroom (Flemming, 1925), ways in which the negative personality traits of the parent became incorporated into child rearing practices (Harris, Gough, & Martin, 1950), and the belief that a mother's ongoing concerns about the sleep of a 2 year old indicated greater potential for psychopathology (Ragins & Schachter, 1971). In reviewing the historical data, it soon became apparent that a thorough analysis could not be conducted due to the differences in reported variables. Researchers would actually need to conduct dose-response studies to examine the effect of different allotted amounts of sleep on alertness, cognitive, and adaptive functioning to effectively research the impact of sleep (Matricciani, Olds, Blunden, Rigney, & Williams, 2012). The majority of historical research is survey based with vastly different criteria analyzed. Furthermore, methodological rigor, including demographic reporting, was not at the same level as seen today.
A summary overview of published historical data on preschoolers' sleep patterns is presented in Table 1. As indicated above, early researchers presented the first wave of information about preschoolers' actual sleep. Flemming (1925) found that 24 to 36 month old children slept a total of 12 hours, 49 minutes per day, including naps. She found little variation with children aged 36 months to 41 months, who were reported to have slept a total of 12 hours, 34 minutes per day with naps. Only three years later, Foster et al. (1928) reported significantly different findings from their study of the sleep patterns of children of varying ages. The total mean nighttime sleep for children aged 30 to 35 months was 10 hours, 57 minutes. Children aged 36 to 41 months were found to have a mean night-sleep total of 11 hours, 4 minutes. Only 7.4% of children aged 30 to 35 months did not take a nap, and 12.5% of children aged 36 to 47 months did not take a daily nap.
There was no known published research on preschoolers' sleep patterns between the late 1930s and Klackenberg's 1968 study (as cited in Iglowstein, Jenni, Molinari, & Largo, 2003). Klackenberg found a mean total sleep time of 12.5 hours for 3 year olds. Only twelve years later, Jacklin, Snow, Gahart, and Maccoby (1980) found a total sleep time of 11.8 hours per night (SD = 2.96) for 33-month-old children and examined the possible influence of gender on sleep patterns, finding no significant differences in sleep patterns by gender. In 1999, Lavigne et al. found that 3-year-olds were reported to have slept a mean total of 11 hours, 45 minutes over a 24 hour period, including naps. They also reported that nap-time sleep and overall sleep decreased as the children's age increased. This review of the published data shows that children today sleep less than the average 3-year-old in the 1920s and 30s, and those historically reported children slept for shorter lengths of time than experts of the day recommended. An ongoing trend for at least 90 years involves experts prescribing longer amounts of sleep than preschoolers ever seem to obtain.
Historical overview of bedtimes and wake times. Total sleep is only one of the sleep factors that are associated with human health and well-being. As such, researchers have also examined bedtimes and wake times. To illustrate, in a historical study that logged preschoolers' bedtimes, Chant and Blatz (1928) studied 16 children and found a modal bedtime of 6:30 PM (SD = 39 mins). More than 65 years later with a much larger sample, Armstrong, Quinn, and Dadds (1994) studied 351 children aged 25-38 months. A bedtime between the hours of 6:00 and 8:00 PM was found to be the norm for 64.4% of the sample. A bedtime between 8:00 and 10:00 PM was reported for 30.7% of the children, and only 4.1% were reported to have had a bedtime at or after 10:00 PM.
Only a few years later, Lavigne et al. (1999) found that the 3 year olds in their study had a mean bedtime of 8:58 PM. The study was conducted in Chicago. Although it might be posited that children who live in urban environments are more likely to have later bedtimes than their rural counterparts, there is still no empirical evidence to support this position. In addition to lending support to the position that children today go to bed later than their peers of earlier generations, Lavigne et al.'s study also provides the first-known published empirical account of preschooler's wake times. This same study also appears to be on the forefront in considering preschool children's sleep in the context of socioeconomic factors.
Lavigne et al. (1999) found the mean wake time for 3 year olds was 7:29 AM. They also found that naps decreased with age. Furthermore, their findings showed that children from a lower socioeconomic environment went to bed later, woke for the day later, took longer naps, and napped more frequently. Lavigne et al. also reported that the lower socioeconomic sample logged more total sleep in a 24 hour period. Extending this research to a sample outside of the U.S., Ottaviano, Giannotti, Cortesi, Bruni, and Ottaviano (1996) found that 25-48 month old children in an urban area of Rome went to sleep on average at 9:43 PM (SD = 43 mins). Ottaviano et al. (1996) also found a significant positive association between later onset sleep time, overall lower total night-time sleep in a 24 hour period, and total night-time sleep across all age groups (M = 10 hours, 30 minutes; SD = 45 mins). Ottaviano et al. also reported that the average reported rise time was 7:08 AM (SD = 45 mins). The apparent differences in bedtimes, wake times, and total sleep reported by Ottaviano et al. and Lavigne et al.'s study of a U.S. urban sample lead to the additional question of cultural and/or geographic differences in preschooler bedtimes, wake times, and total amount of sleep.
In another international study, Iglowstein et al. (2003) examined generational sleep trends. This study, conducted in Zurich, recruited cohort groups of children born between 1974 through 1993. Iglowstein et al. recruited 450 children in three birth cohorts (1974-1978, 1979-1985, and 1986-1993) to examine trends in total sleep, bedtimes, and wake times over time. Three year-olds in the first cohort were reported to have slept an average of 12.5 hours in a 24 hour period (SD = 1.1 hrs) and to have had a night-time sleep duration of 11.43 hours (SD = 0.8 hrs). Fifty percent of the children were found to nap. Interestingly, children in the second and third cohort groups showed a pattern of going to bed later but getting up at approximately the same time.
Returning to the U.S., Ward, Gay, Anders, Alkon, and Lee (2008) studied 52 children aged 3-5 and found the mean sleep time to be about 10 hours (SD = 38 mins). Children who slept during the day reportedly slept less at night. It was also found that children tended to nap when presented with an opportunity to do so.
Although focused on older children, aged 5-18, Matricciani et al.'s (2011) historical analysis of actual and imputed data from sleep studies from 1905 through 2008 found a total sleep decrease of 1 hour over the targeted period. This lends support to the conclusion reached throughout this review: children today sleep less than children in earlier times. Matricciani et al.'s analysis also showed a trend toward later bedtimes while wake times remained relatively constant. They also noted differences between sleep during the school week and on weekends, but it should be noted that this was a school aged population. This is in contrast with the findings of a longitudinal Icelandic study that found that children in the early years of life maintained the same approximate sleep schedule during both the week and weekend (Thorleifsdottir, Bjornsson, Benediktsdottir, Gislason, & Kristbjarnarson, 2002).
A review of the literature shows a wide range of total sleep times, bedtimes, wake times, and napping patterns. A trend towards later bedtimes, decreased naps, and lesser amounts of total sleep over time is also evident. These differences may be due to varied norms across a range of geographic areas. One question that is yet to be examined is the influence, if any, of a rural or urban environment on preschoolers' sleep patterns. Differences in sleep patterns related to racial, cultural, and socioeconomic characteristics have also emphasized the need for more research in this area as well.
Sociocultural influences on preschoolers' sleep. Bates et al. (2002) examined 4-5 year old children's sleep patterns in a mainly lower income community sample. Children in this study were found to go to bed about 1 hour later than Weissbluth (2003) found in his 1980 study of 2,019 White, mid-western, middle-class children. Acebo et al. (2005) also considered the influence of family socioeconomic status (SES) in their examination of the sleep/wake patterns of 169 children in the U.S. based on activity monitoring and maternal report. Their findings showed a significant association between SES and the sleep/wake pattern. Acebo et al.'s findings indicate that children from higher SES status families tended to get out of bed earlier; spend less time in bed during the night; and demonstrated greater sleep efficiency, defined as longer periods of continuous sleep. They also found less nightly variability, that is bed times and length of sleep, among preschool children from high SES families than their lower SES peers.
Moving from SES to racial/cultural influences, Hale et al. (2009) found 72% of European American mothers reported a regular use of a bedtime in contrast with 65% of Latina mothers, 66% of African American mothers, and 68% of mothers who identified as members of other racial/ethnic groups. The differences between the groups are small yet suggest that bedtimes may be influenced by sociocultural as well as individual needs. Of note, Hale et al. found that 86% of the families in which a father or father figure was present were more likely to report having and using a bedtime than those in which a father figure was not present. The father's presence was not broken down by racial/cultural influences.
Another U.S. study found differences between 2-8 year old African American and European American children's sleep patterns (Crosby, LeBourgeois, & Harsh, 2005). Napping and nighttime sleep differences were reported between the 2 groups by age 3. African American children were 76.5 times more likely to take a nap and logged less night-time sleep than their European American peers. Racial/ethnic differences in how mothers manage and perceive the sleep of their 35.5 (SD = 2.34) month old children was also seen in a study comparing European American, African American, and Latina mothers (Milan, Snow, & Belay, 2007). Mother's education also appears to be influential in preschooler sleep. Although not specifically focused on preschoolers, a study of elementary-school-aged students' sleep in Saudi Arabia offers additional perspectives. BaHammam, Bin Saeed, Al-Faris, and Shaikh (2006) found that children of mothers who reported lower levels of formal education had significantly later mean bedtimes than children whose mothers had a college or post college education. This study also found that student participants whose mothers had a high school education or higher, as well as those whose mothers were working outside the home, logged more total sleep on weekdays than their peers whose mothers had less formal education and were not working outside the home. The total sleep time for girls was higher than boys but no significant difference was found when the results were stratified by age.
It is clear from this review of published data that less is known about typically developing preschoolers' sleep patterns than is commonly believed. Thus the first purpose of this study was to identify normative sleep patterns--that is bedtimes, wake times, and total hours slept in a present-day U.S. sample of typically developing 3 year-olds. The second purpose was to compare the data collected with widely held recommended sleep guidelines (i.e., NSF, 2011). The third purpose was to complete a historical comparison of relevant preschoolers' sleep patterns from published data. Lastly, given the apparent variations in sleep patterns reported above, the fourth and final purpose of this study was to consider the influence of two previously identified sociocultural factors, that is race/ethnicity and socioeconomic status, on preschoolers' sleep patterns.
This study utilized secondary data collected as part of comprehensive evaluations for possible referral to school-district based intervention services in two suburban counties in New York State. The majority of referrals were for articulation issues, followed by overall speech delays, gross motor functioning, fine motor functioning, and then behavioral concerns. Parents wishing to refer their children for possible therapeutic services initiate the process through the Committee on Preschool Special Education (CPSE) for their school district. All children close to 3 years of age, and until they enter kindergarten, are served by this department. Each child receives a psychological evaluation, which includes a social history, to rule out any major developmental delay that would result in referral for more intensive services. Services from birth until 3 years of age are provided by Early Intervention. Children who receive services through Early Intervention for the delays mentioned previously are transferred to CPSE once their 3rd birthday is reached. The children undergo a full re-evaluation that includes a psychological evaluation, social history, educational evaluation, and an evaluation related to the area of concern to ensure services are required and for treatment planning purposes.
All children lived in the extended areas of Westchester and Rockland counties in New York State. The counties are large suburbs outside of New York city. The results of the evaluations show that the large majority of children were typically functioning and representative of the community in which they lived. The mean FSIQ score for our sample was 99.45. Behavior Assessment System for Children (BASC-2) scores indicated the overwhelming majority were in the Adequate range of adaptive functioning. The vast majority of children who attended preschool were in a regular education setting. Children with disabilities that interfered with daily functioning tended to comprise a small minority of the participants, as they were usually involved with a site-based program, and would receive the full evaluation on site. Thus, this sample is most appropriately considered a community sample. The results of screenings confirmed that the vast majority of children in the sample were typically developing. Confirming this determination, results of a longitudinal study (MGT, 2007) show that few preschool children were classified subsequent to early intervention screenings such as the one that generated the data set from which this secondary data was derived. Furthermore, this same study found that 22% of preschool children who initially received services were declassified by kindergarten.
This community based sample was comprised of 874 children, ranging in age from 22 to 63 months, with a mean age of 40.01(SD = 8.26) months, a modal age of 33 and 35 months, and a median age of 36.00 months. Three-hundred-twenty were female and 554 were male. Parents or legal guardians reported their children's race/ethnicity as follows: European American or White (733; 83.86%), Latino or Hispanic (48; 5.49%), African American (54; 6.17%), and Asian or Asian American (39; 4.46%). The population was over representative of European Americans as compared to the make-up of the geographic area.
Using zip codes and U.S. census reports, we estimated that 74.3% of the children (n = 649) lived in middle income areas, 18.8% (n = 164) in higher SES areas, and 7.0% (n = 61) in lower SES areas. The majority of the female caregivers reported having attained at least a college degree (75.3%). The remaining caregivers self-reported having some college (15.9%), having a high school degree (7.6%), or not finishing high school (.9%).
Parent/caregiver reports of preschoolers' sleep. The first author contributed to the compilation of the secondary data set by conducting structured interviews that asked the parent(s)/caregiver to indicate their child's average bedtime, wake time, and total hours of night-time sleep as representative of current patterns. Parent(s)/caregivers' reports of their child's sleep patterns were used because of the nature of the structured social history interview. Actigraphy, electronic monitoring of sleep cycles, has been used with increasing frequency. However, parent(s)/ caregiver reports have been shown to more accurately represent children's regular sleep behaviors over time (Geiger, Achermann, & Jenni, 2010) and are positively correlated with objective sleep measures (Matricciani et al., 2011). This is comparable with Bodnarchuk and Eaton's (2004) finding that parents' reports of children's development are more accurate than professional evaluators' reports. Parents and caregivers were also asked to indicate whether their children slept through the night and if they napped on a regular basis.
Prior to conducting the analyses that follow, the data was screened for outliers, using box plots, graphical analysis, and visual inspection. Several outliers on all measures: total night-time sleep, bedtimes, and wake times, were identified. It was determined through individual case review that the reported data accurately represented individual variations. As a result, no data was excluded. The full sample of 874 was included in the analyses that follow.
Sleep patterns of children in this sample. Preschoolers in this study averaged 10 hours, 54 minutes (SD = 57 mins) of total night-time sleep. The mean bedtime was 8:15 PM (SD = 51.6 mins) and the mean wake up time was 7:10 AM (SD = 49.8 mins). Table 2 presents means, standard deviations, and ranges for bedtimes, waketimes, and total sleep. Sleep duration was computed from each reported bedtime and wake time. There was no significant relationship between age in months and bedtimes, r(874) =.05, p =.142. A small, yet significant, correlation was found between age and wake-up time, r(873) =.099, p =.004. Children showed a tendency towards getting up later as they increased in age. No significant correlation was found between the age of the child and hours slept, r(874) =.029, p = .334 (See Table 3). Parents reported that 3-year-old children tended to get up at the same time during the work week and on weekends.
The study found that children who went to bed later also tended to wake up later, r(871) =.376, p =.000. However, the results also show that children who went to sleep later tended to get less sleep, indicating a negative relationship between bedtimes and total hours of sleep, r(873) = -.570, p = .000.
The bedtimes, wake-up times, and hours slept for children who took naps were also compared to those who did not nap. The mean bedtime for children who napped (n = 386, 44%) was 8:21 PM (SD = 53 mins), and the mean bedtime for children who did not nap was 8:10 PM (SD = 50 mins). This 11 minute difference was found to be significant, t(861) = 3.190, p =.001. Children who took a nap had a significantly later bedtime than children who did not take a nap. Children who took a nap woke at a mean time of 7:07 AM (SD = 47 mins), while children who did not take a nap got up at 7:14 AM (SD = 50 mins). Thus, children who took a daily nap got up 7 minutes earlier on average than children who did not. This difference was found to be significant, t(860) = - 2.148, p =.032. Although children who napped slept an average of 18 minutes less per night (10 hours, 45 minutes, SD = 59 mins), significantly less, t(862) = -4.421, p =.000, than those who did not nap (11 hours, 3 minutes, SD= 54 mins), their parents/caregivers' reported they logged more total sleep over a 24 hour cycle. A significant difference, t(873) = -2.194, p =.028, was found between girls and boys related to amount of nightly sleep. Girls were found to sleep about 10 minutes more than boys on a nightly average.
Not surprisingly, in our preliminary analyses, we found significant collinearity, as measured by high levels of tolerance and Variance Inflation Factor (VIF) scores among children's bedtimes, wake times, and total hours of sleep. High tolerance and VIF scores are measures of the degree of shared variance and the likelihood of artificially inflated multivariate analysis results. Multicollinearity was also evident in mothers' report of their children's racial/ethnic identity, their highest level of educational attainment, and their child(ren)'s bedtimes, wake times, and total hours of sleep. We also found a significant negative correlation, r(704) = -.18, p < .01, between mothers' highest level of education and racial/ethnic identity among the mothers in this predominantly European American, college-educated sample. As a result, we restricted the within-sample analyses that followed to correlational analysis and ANOVAs with appropriate post-hoc analysis.
Comparing Sample Results with Expert Guidelines
As shown in Table 2, the 3-year-old children in this sample slept 10 hours, 54 minutes per night, just shy of the 11 hours recommended by the NSF (2011). The results also show wide individual variability in mean total night-time sleep with reported sleep-times ranging from 6 hours, 45 minutes to 14 hours per night (SD = 57 mins).
Putting Sample Results in a Historical Context
To answer the third research question about the change, if any, in preschool children's sleep patterns over time, we conducted a systematic review of the empirical literature. Using a variety of academic databases (e.g., Psyclnfo) we identified published reports of 3 year-old's bedtimes, wake times, and total hours of nighttime sleep, much of which is described in the introduction. To date, most children's sleep research has and continues to rely on parent/caregiver report. However, more recently, physiological recording devices (e.g., actigraphs) have been utilized. Both methods are currently considered appropriate for data gathering, however, as discussed above, parent report is considered more accurate than electronic methods (Bodnarchuk & Eaton, 2004; Geiger et al., 2010; Matricciani et al., 2011).
The mean total sleep time for 3 year-olds reported in the 1920s (Chant & Blatz, 1928; Flemming, 1925; Foster et al., 1928) was 12 hours, 36 minutes. In contrast, the mean total sleep time reported by U.S. researchers in the 1990s was 11 hours, 28 minutes, and the mean reported by U.S. researchers in the 2000s was 10 hours, 22 minutes. The results of the current study show a mean total night-time sleep for 3 year-olds of 10 hours, 54 minutes, a little higher than the average found in the 2000s, but still lower than reported earlier.
In contrast, Ottaviano et al.'s (1996) study of children in Rome, found mean total night-time sleep of 10 hours, 33 minutes, lower than the mean reported by all of the U.S researchers, including the current study. Additionally, Iglowstein et al.'s (2003) study of three cohort-groups in Zurich found total mean sleep-times ranging from 11 hours, 43 minutes for the cohort born in 1974-1978 to 11 hours, 28 minutes for the cohort born 1986-1993.
This review also shows that preschool children are going to bed, on average, much later than in the 1920s. Chant and Blatz (1928), the only researchers found in the 1920s to publish bedtime data, reported a modal bedtime of 6:30 PM. In contrast, the mean bedtime reported by U.S. researchers in the 2000s was 8:36 PM. The children in this study were reported to have had a mean bedtime of 8:15 PM. Having later bedtimes while maintaining a constant wake time is consistent with findings for children aged 5_18 (Matricciani et al., 2011).
Once again, the international data differs from the U.S. data. Ottaviano et al. (1996) reported average bedtimes of 9:48 PM and 8:58 PM for their sample of children in Rome. In contrast, Iglowstein et al.'s (2003) study of children in Zurich reported bedtimes ranging from 7:35 to 8:07 PM.
Sleep Differences by Racial/Ethnic and Socioeconomic Status
We also analyzed sleep patterns by parents' report of their child(ren)'s race/ ethnicity as African American, Asian American, European American, or Latino/a. A breakdown of sleep patterns by race/ethnicity can be seen in Table 4. ANOVA results for this sample show that bedtimes, wake times, and total hours of night-time sleep were significantly influenced by participants' racial/ethnic identity, F(3, 867) = 25.690, p = .000. A greater level of variability (SD = 1 hr, 15 min) was seen in total nightly sleep African American children received compared with other groups. However, given the significant within-group variability of all groups, this level of variability was not significantly different. There was also no significant difference between racial/ethnic group members in naps or total hours slept per night.
In terms of total night-time hours slept, parents of children identified as European American reported the longest sleep times, while Asian American children were reported to have slept fewer hours than any other group. ANOVA results show a significant between-groups difference in the average total number of hours per sleep reported, F(3, 870) = 12.667, p = .000. Using Dunnett's post-hoc analysis revealed no significant difference (p = .147) between reports that European American children slept an average of 10 hours, 59 minutes per night and reports that Latino/a children slept an average of 10 hours, 41 minutes per night. However, Dunnett's post-hoc analysis also found significant differences between reports that African American children slept an average of 10 hours, 26 minutes per night, Asian American children slept an average of 10 hours, 18 minutes per night, and European American children slept an average of 10 hours, 59 minutes per night.
Similarly, European American children were found to have the earliest bedtimes (8:10 PM), with each of the other groups showing a significant difference in bedtimes as compared with this group. In comparison with European American children, Latino/a children had an average reported bedtime of 8:37 PM, African American children had an average reported bedtime of 8:43 PM, and Asian American children in this sample had the latest average reported bedtime at 8:58 PM. Correspondingly, European American children woke up earliest, on average with a mean wake time of 7:09 AM (SD = 48 mins) and Asian American had the latest mean wake up time (7:22 AM, SD = 60 mins).
Sleep Differences by Mother's Highest Level of Formal Education
Children's mean bedtimes, waketimes, and hours of night-time sleep, arrayed by mothers' highest level of formal education are displayed in Table 5. Overall, we found a significant positive association between mothers' highest level of formal education and their child(ren)'s reported sleep patterns, F(3, 654) = 3.777, p = .010. More specifically, our findings show a significant positive association between mothers' educational level and their child(ren)'s bedtime, r(658) = - .114, p < .01, and wake times, r(658) = -.102, p < .01, but not between mothers' educational level and their child(ren)'s mean hours of night-time sleep, r(660) = .012, p = .754.
Additionally, our results show that mothers with the lowest levels of formal education reported the latest preschool child(ren)'s bedtimes and earliest wake times and, correspondingly, the lowest mean totals of night-time sleep. Conversely, mothers with the highest levels of formal education reported the earliest bedtimes. However, the difference between maternal education groups was not significant with the exception of the very small (n = 8) subsample of children whose mothers did not graduate from high school. Those children slept significantly fewer hours per night than the children whose mothers reported higher levels of formal educational attainment. We did not find any evidence that mothers' educational level was associated with total hours of sleep.
This study identified sleep patterns in a current U.S. community sample, compared those results with generally accepted guidelines, and reviewed those results within a historical and sociocultural context. The results provide a large community-based normative sampling of preschool children's sleep patterns. This is important as most sleep research, particularly children's sleep research, has been focused on sleep disorders with clinical populations (Bates et al., 2002; HHS, 2003). This is also important given that sleep is central to children's development and healthy human physical and psychological functioning (Bates et al., 2002; Gaylor, 2010; Hale et al., 2010; HHS, 2003; Lavigne et al., 1999).
The average child in this sample sleeps 10 hours, 54 minutes per night. He or she goes to bed at 8:15 PM and wakes up at 7:10 AM, seven days a week. The older the preschool child, the more likely it is that he or she gets up a little later. Nappers, comprising 44% of the sample, went to bed later and woke up earlier yet logged more total sleep than the non-nappers. However, there is no average child. The results also showed significant and far ranging individual variations in preschoolers' sleep patterns ranging from 6 hours, 45 minutes to 14 hours and similar individual differences in bedtimes and wake up times as reported in Table 2. The results of this study also lend support to earlier research (Crosby et al., 2005; Hale et al., 2009; Ottaviano et al., 1996) that found racial/ethnic, socioeconomic, and cultural differences in preschool children's sleep patterns. Notwithstanding the established guidelines, these results suggest that healthy, typically- developing children, like adults, may have very different sleep needs and patterns than those that are commonly prescribed. Individual variations are being taken into account to a greater degree, and this study supports that recommendation.
The third purpose of this study was to consider the current data in a historical context. This review confirms and extends Matricciani et al.'s (2011) finding that 5-18 year old school children today sleep fewer hours per night than their peers just a few generations ago. More specifically, preschool children in this study slept an average of 10 hours and 54 minutes per evening. In comparison with the data presented in Table 1, the average child in this sample slept nearly 42 minutes less per night than Chant and Blatz (1928) reported. Although the total sleep for this sample was roughly equivalent with the 10 hours and 33 minutes reported by Ottaviano et al. (1996), it is still 34 minutes less total sleep than Lavigne et al. (1999) and Iglowstein et al. (2003) reported for their most recent cohort. There is one notable exception to this trend: Acebo et al.'s (2005) small-scale (N = 21) study that found mean total sleep of 10 hours, 5 minutes for boys and 10 hours, 6 minutes for girls. The different results may be due to the fact that Acebo et al. used actigraphy as opposed to parent/caregiver reports, the norm for sleep research to date (HHS, 2003) and the method employed by all the aforementioned researchers. This is also important because recommendations concerning total sleep for children do not take into account time the preschooler rests in bed without sleeping.
The results also show that children today are also going to bed later than was reported in the past. This suggests that preschooler sleep patterns are influenced by changing times and norms. Bedtimes and wake times may also be influenced by parents' work patterns and vary according to geographic location. Although many psychologists, educators, and other professionals sense this information, this study, the first known study to provide quantitative current data in a historical context, confirms and extends that general understanding.
The final purpose of the study was to examine socioeconomic and cultural differences related to preschoolers' sleep. This is a relatively recent focus in sleep research. Although the majority of participants were European American, there was sufficient representation of children who were identified as members of commonly under-studied populations, allowing for an analysis of sleep patterns by race/ethnicity and SES. The results of this study lend support to other research findings (e.g., Hale et al., 2009) that show sleep is culturally and socially influenced. Bedtimes appear to be particularly influenced by culture. European American preschoolers had earlier bedtimes and earlier wake times than African American, Latino/a, and Asian American preschoolers. The findings also show that European American preschoolers generally sleep longer than their peers who are identified as members of other racial/ethnic groups. We also found that maternal education was closely linked to sleep patterns, yet this finding may not be generalizable given the limitations of the sample.
There were several limitations to the current study. First, the sample was predominantly European American and middle class. Given the lower numbers of racial/ethnic minority children in the sample when compared to European American children, the associations between race/ethnicity and socioeconomic status may not be as generalizable as the rest of the results. The small number of mothers who did not graduate from high school were also overly represented in the African American and Latino/a subgroups and resided in zip codes with higher material poverty levels. This was clearly a limitation of the sample and study.
Preschool children's sleep warrants further exploration, with more deliberately representative samples, to further identify normative patterns of preschoolers' sleep and investigate the association among these patterns, race/ethnicity, culture, and SES. From a psychological and educational perspective, future researchers should further explore the association between normative sleep patterns and related behaviors. This may set the stage for evidence-based prevention and intervention guidelines
The findings of this study, as well as similar studies found in the literature, indicate that preschool children have individual sleep pattern needs. It is critically important that guidelines and recommendations be based on research with typically-developing and community samples. However, we caution psychologists and other concerned adults not to make individual recommendations based on statistical averages as this study also shows that there is wide variation in preschooler's sleeping patterns. Parent(s)/caregivers would benefit from the reassurance that they are likely in the best position to determine bedtimes and wake times based on personalized observations of their children and resultant daily functioning levels. This would likely reduce the stress and strain many parents and children experience in attempting to meet unsupported sleep guidelines and therefore contribute to more optimal parent-child relationships (Aring & Renk, 2010). In addition, children who get their individualized sleep needs met are more likely to thrive physically, cognitively, adaptively, and emotionally. Furthermore, given the importance of sleep in preschool children's lives and development, professional as well as parent/ caregiver recognition and respect of individual as well as group optimal sleep patterns appear to be the first step towards meeting this goal. Determining sleep patterns should be a key developmental question as its importance continues to grow with emerging research.
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Kathleen Keefe-Cooperman Long Island University & Peggy Brady-Amoon Seton Hall University, U.S.
Correspondence concerning this article should be sent to Kathleen Keefe- Cooperman, Department of Counseling and Development, Long Island University, 720 Northern Blvd., Brookville, NY 11548-1319 USA. Email: Kathleen.Keefe-Cooperman@liu.edu, Phone: (914) 673-3321, Fax: (866) 516-9363.
Table 1 Preschool Sleep Pattern Data over Time Author (Year) Location N Age Flemming (1925) U.S.A. Not reported 2.5-3 yrs. 3-3.5 yrs Chant & Blatz U.S.A 9 3-3 y, 11 mo (1928) Not in daycare 7 3 y Daycare Foster et al. U.S.A. 112 2-6-2-11 yrs 96 3-3.5 Jacklin et al. U.S.A 72 33 mo (1980) Ottaviano et al. Rome 769 25-48 mo (1996) Lavigne et al Chicago 124 3 yrs (1999) U.S.A Iglowstein et al. Zurich 455 3 yrs (2003) Birth Cohorts 74-78 79-85 86-93 Acebo et al. Rhode 21 36 mo (2005) Island U.S.A Boys 12 Girls 9 Author (Year) Bed Time Wake Time Nap Time Flemming (1925) Chant & Blatz 6:30 (39) lh, 29m (1928) mode 1h, 14m Foster et al. Jacklin et al. (1980) Ottaviano et al. 9:48 (43) 7:08 (45) 1h, 50m (44) (1996) Lavigne et al 8:58 7:29 1h, 17m (1999) Iglowstein et al. (2003) Birth Cohorts 74-78 7:35 (35) 7:18 (44) 79-85 7:53 (41) 7:27 (46) 86-93 8::07 (42) 7:35 (50) Acebo et al. (2005) Boys 8:52 (47) 7:20 (34) Girls 8:40 (70) 7:19 (68) Author (Year) Total Total Hours Night Sleep Slept Flemming (1925) 12h, 49m 12h, 34m Chant & Blatz llh, 36m 12h,52m (1928) Foster et al. 10h, 57m (44) 12h, 30m (47) 11h, 4m (40) 12h, 17m (44) Jacklin et al. 11hr, 49m (1980) (2h, 58m) Ottaviano et al. 9h, 19m (56) 10h, 33m.(73) (1996) Lavigne et al 10h, 32m 11h, 28m (1999) Iglowstein et al. (2003) Birth Cohorts 74-78 11b, 43m 79-85 11h, 34m 86-93 11h, 28m Acebo et al. (2005) Boys 10h,5m (.8) Girls 10h, 6m (.5) Note. All times are listed in hours (h) and minutes (m); standard deviations (SD) are provided in parentheses. Table 2 Summary of Means and Standard Deviations Measure n M SD Range 1. Bed-time 874 8:15 51.6 6-12 2. Wake-time 873 7:10 49.8 4-10:30 3. Total sleep 874 10h, 54m 57.0 6h,45m-14h Note. Bed-time and wake-time are reported as time of day, in hours. Total sleep is reported in hours (h) and minutes (m). Standard deviations (SD) are reported in minutes. Table 3 Intercorrelations between Children's Mean Bed-Times, Wake-Times, Mean Total Hours Night-Time Sleep, Gender, Race/Ethnicity, and Mother's Highest Level of Formal Education (N = 658) 1 2 3 4 5 6 1. Bed-times. 38 ** -.57 ** -0.03 .25 ** -.11 ** 2. Wake-times .53 ** 0.06 .53 ** -.10 ** 3. Mean night- .07 * -.20 ** 0.01 time sleep 4. Gender 0.01 -0.03 5. Race/ -.18 ** ethnicity 6. Mother's education * p < .05 ** p < .01 Table 4 Mean Bed Time, Wake Time, and Total Hours of Night-Time Sleep by Race/Ethnicity (N=872) Race/Ethnicity n Bed Time Wake Time Hours Night (% Total (SD) (SD) time sleep Sample) (SD) White/European 731 (83.9%) 8:10 (48m) 7.09 (48m) 10h, 59m (53m) Black/African 54 (6.2%) 8:44 (63m) 7:11 (53m) 10h, 26m (75m) Latino/a 48 (5.5%) 8:37 (56m) 7:17 (49m) 10h, 41m (55m) Asian/Asian 39 (4.5%) 8:58 (68m) 7:22 (60m) 10h, 18m (64 m) Table 5 Mean Bed Time, Wake Time, and Total Hours Night-Time Sleep by Mother's Highest Level of Formal Education (n=659) Education n Bed Time Wake Time Hours Night Level (% Total (SD) ( SD) time sleep Sample) (SD) Did not 8 (.9%) 8:30 (13m) 6:41 (93m) 10h, 11m (60m) graduate HS High School 50 (7.6%) 8:33 (55m) 7:35 (66m) 11h, 1m (57 m) graduate Some college 105 (15.9%) 8:25 (51m) 7:19 (54m) 10h, 53m (63 m) College 496 (75.3%) 8:15 (51m) 7:09 (45m) 10h, 54m (54m) degree or higher…
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Publication information: Article title: Preschoolers' Sleep: Current U.S. Community Data within a Historical and Sociocultural Context. Contributors: Keefe-Cooperman, Kathleen - Author, Brady-Amoon, Peggy - Author. Journal title: Journal of Early Childhood and Infant Psychology. Volume: 8. Publication date: Annual 2012. Page number: 35+. © 2009 Pace University Dba: Pace University Press. COPYRIGHT 2012 Gale Group.
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