Table 2

Sleep variables in early childhood and socio-emotional functioning at 24 months

Sleep variables in early childhood
Mean (SD)MedianMinimumMaximum
BISQ total sleep duration, hours
 3 months14.3 (1.8)14.56.020.0
 8 months13.3 (1.2)13.59.020.0
 18 months12.3 (0.9)12.28.016.0
 24 months11.9 (0.9)12.08.315.0
BISQ proportion daytime sleep
 3 months36.2 (8.2)36.410.077.8
 8 months25.5 (6.5)25.010.053.8
 18 months16.7 (4.9)16.06.039.3
 24 months15.7 (5.0)15.90.040.0
BISQ bedtime, hh:mm
 3 months21:48 (1:11)21:3218:0002:10
 8 months20:52 (0:54)21:0018:2001:30
 18 months20:42 (0:42)20:3018:3023:40
 24 months20:55 (0:40)21:0018:4523:30
ISQ sleep-onset latency
 3 months1.9 (1.8)1.00.06.0
 8 months1.1 (1.2)1.00.06.0
 18 months1.0 (1.1)1.00.06.0
 24 months1.4 (1.5)1.00.06.0
ISQ number of night wakings
 3 months1.6 (1.3)2.00.05.0
 8 months2.0 (1.4)2.00.05.0
 18 months1.0 (1.2)1.00.05.0
 24 months1.0 (1.0)1.00.05.0
Socio-emotional functioning at 24 months
Symptom scoresMean (SD)MedianMinimumMaximum
 BITSEA externalising3.1 (2.2)3.00.011.0
 BITSEA internalising1.6 (1.5)1.00.09.0
 BITSEA dysregulation3.1 (2.4)3.00.012.0
  • BISQ variables are all continuous variables, while ISQ sleep-onset latency and ISQ number of night wakings are categorical variables: in ISQ sleep-onset latency, 0=<10 min; 1=10–19 min; 2=20–29 min; 3=30–39 min; 4=40–49 min; 5=50–59 min; and 6=≥60 min; and in ISQ number of night wakings, 0=0 times/night; 1=once/night; 2=twice/night; 3=three times/night; 4=four times/night; and 5=five times/night.

  • BISQ=Brief Infant Sleep Questionnaire; BITSEA, Brief Infant-Toddler Social and Emotional Assessment; ISQ, Infant Sleep Questionnaire.