In this study by Jakubowski and colleagues, they found that frequent napping may interfere with nocturnal sleep during adolescence.
They found that in a sample of adolescents who slept on average significantly less than the recommended 9 hr per night, their results suggest daytime napping is a prevalent behavior. Participants completed sleep diaries every morning and evening for one school week and weekend, simultaneous with actigraphy measures. Actigraph devices, such as actiwatches, are worn on the wrist and record movements and accelerations; using activity counts and diary records of bedtime and wake time, periods of sleep and wake can be estimated. 89% of adolescents demonstrated at least one actigraphy-assessed nap and 62% reported at least one diary-assessed nap during the week-long study period. They reported that adolescents napped on about one third of the days, as assessed by actigraphy, and on about one fifth of days, as assessed by sleep diaries. A temporal (related to time) relationship emerged between short nocturnal sleep duration leading to more daytime napping and vice versa, measured either by actigraphy or by diary. Furthermore, they suggested that the pattern of results was largely confirmed by congruently measured naps (assessed by both actigraphy and diary), which supports to their individual findings based on actigraphy and diaries.
Karen P. Jakubowski, Martica H. Hall, Laisze Lee, and Karen A. Matthews
University of Pittsburgh, United States
The researchers stated that the primary objective of the study was to examine the temporal relationship between nocturnal sleep and daytime napping in healthy adolescents who participated in a week-long study of actigraphy and diary measures of sleep.
They tested whether (a) shorter nocturnal sleep, lower sleep efficiency, and self-reported sleep quality predicted both the occurrence and duration of napping the following day; and (b) occurrence and duration of napping predicted shorter nocturnal sleep, lower sleep efficiency, and self-reported sleep quality that night.
They also investigated whether napping predicted a later bedtime, which would lead to shorter nocturnal sleep. A secondary objective was to describe the frequency and duration of daytime naps in healthy adolescents, as well as potential differences in napping associations by race and gender.
The researchers remarked that to their knowledge, only two studies had examined the temporal relationships between napping and nocturnal sleep, albeit in samples of middle-aged and elderly adults. They noted that given adults may nap for different reasons than adolescents (e.g., more free time due to retirement, chronic illnesses), it was worthwhile to investigate whether temporal relationships between naps and nocturnal sleep are apparent in healthy adolescents.
The researchers tested 250 adolescents between the ages of 14 and 19 enrolled at a single public high school. Participants completed sleep diaries every morning and evening for one school week and weekend, simultaneous with actigraphy measures. They also completed sleep questionnaires and measures of cardiovascular risk. Following exclusions, the researchers retained a final analytic sample of 236 participants.
ScientiFix tip: The researchers noted a mismatch between actigraphy-assessed and diary naps. It appeared that diary naps reflected fewer and longer nap episodes, whereas actigraphy-assessed naps reflected more frequent and shorter nap episodes. However, when analyses were constrained to actigraphy-assessed naps with a congruent, or matching, diary nap, the pattern of results was similar to that found with actigraphy-assessed or diary-reported naps alone. They suggested that it is likely that diary and actigraphy methods obtain somewhat different information about napping. For example, their results suggested that actigraphy may capture a broader range of nap behavior, including planned and also unplanned naps that may have spontaneously occurred in response to sleepiness, which they suggested may explain why more actigraphy-assessed naps were captured, but they were of shorter duration. They noted that since napping is a behavior that typically occurs with less regularity than nocturnal sleep, it might have been more difficult for participants to track, especially since they completed the diaries at night prior to bedtime rather than online throughout the day. This is a great example of the possible limitations of self-report measures, and why being able to use more reliable, objective, and automated methods such as actigraphy are likely preferable.