The onset of some adult diseases, e.g., cardiovascular disease, is known to be associated with lifestyles in childhood. The objective of this study was to clarify the relationship between total sleep duration (TSD) and systolic and diastolic blood pressure (SBP and DBP) among 117 children at ages 5-6 years. Parents reported their children's typical bedtimes and wake times for weekdays, and questions about mandatory nap times were answered by the preschool teachers. In the children, the mean TSD, SBP, and DBP were 624 ± 57 (standard deviation) min, 99 ± 10 mmHg, and 62 ± 9 mmHg, respectively. When the children were divided into quartile groups based on TSD, the SBP was significantly higher in the highest group (TSD > 660 min) than in the lowest group (TSD ≤ 585 min). The TSD was significantly correlated with SBP (r = 0.265) but not with DBP (r = 0.105), these relationships were similar when TSD and possible confounders such as age and body mass index were set as independent variables of multiple regression analysis. These findings suggest that sleep duration in preschool children is associated with SBP, and extremely short or long sleep may invite subclinical health problems.

Preschool children with sleep deficit may suffer from autonomic symptoms or hypotension. Heart rate variability, reflecting cardiac parasympathetic and sympathetic activities, and blood pressure were assessed to clarify the effects of nocturnal sleep duration on cardiac autonomic function in 134 preschool children aged 5 and 6 years. Parents reported their children's typical bedtimes and wake times for weekdays. In the children, the mean nocturnal sleep duration (± standard deviation) was 575 ± 42 min. The parasympathetic and sympathetic activities and systolic blood pressure (SBP) were significantly lower in the 80 children with short sleep (nocturnal sleep duration < 10 hrs) than in the 54 children with long sleep ( 10 hrs). Only the SBP was positively correlated with nocturnal sleep duration in the children ( p < 0.001); also, short nocturnal sleep duration was significantly related to hypotension (SBP < 100 mmHg), as judged by multiple logistic regression analysis. Among the children, inverse correlations were seen between the parasympathetic activity and SBP and between the sympathetic activity and diastolic blood pressure ( p < 0.05). These findings indicate that shortening of nocturnal sleep is associated with cardiac autonomic hypofunction and low SBP in preschool children. We suggest that sleep duration is an important predictor for autonomic development in childhood.nocturnal sleep duration; cardiac parasympathetic and sympathetic activities; blood pressure; preschool children

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