Normal sleep patterns in infants and children: a systematic review of observational studies.
This is a systematic review of the scientific literature with regard to normal sleep patterns in infants and children (0-12 years). The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Mean and variability data for sleep duration, number of night wakings, sleep latency, longest sleep period overnight, and number of daytime naps were extracted from questionnaire or diary data from 34 eligible studies. Meta-analysis was conducted within age-bands and categories. In addition, fractional polynomial regression models were used to estimate best-fit equations for the sleep variables in relation to age. Reference values (means) and ranges (±1.96 SD) for sleep duration (hours) were: infant, 12.8 (9.7-15.9); toddler/preschool, 11.9 (9.9-13.8); and child, 9.2 (7.6-10.8). The best-fit (R(2)=0.89) equation for hours over the 0-12 year age range was 10.49-5.56×[(age/10)^0.5-0.71]. Meta-regression showed predominantly Asian countries had significantly shorter sleep (1h less over the 0-12 year range) compared to studies from Caucasian/non-Asian countries. Night waking data provided 4 age-bands up to 2 years ranging from 0 to 3.4 wakes per night for infants (0-2 months), to 0-2.5 per night (1-2 year-olds). Sleep latency data were sparse but estimated to be stable across 0-6 years. Because the main data analysis combined data from different countries and cultures, the reference values should be considered as global norms. Copyright © 2011 Elsevier Ltd. All rights reserved.