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Table 2 Sleep characteristics of participants stratified by sex and setting group

From: Sleep and BMI in South African urban and rural, high and low-income preschool children

  All (n = 198) Boys (n = 98) Girls (n = 100) P-value Rural Low (n = 111) Urban Low (n = 65) Urban High (n = 22) P-value
Average
 Bedtime (hh:mm) 20:08 (19:32, 21:02) 20:12 (19:38, 21:12) 20:01 (19:22, 21:00) 0.085 19:38 (19:11, 20:08) 21:20 (21:01, 21:41)c 19:56 (19:35, 20:22) < 0.001
 Wake-up time (hh:mm) 06:40 (06:22, 07:09) 06:42 (06:22, 07:18) 06:39 (06:22, 07:00) 0.242 06:26 (06:11, 06:44) 07:11 (06:53, 07:32)c 06:43 (06:21, 07:19) < 0.001
 Nocturnal time-in-bed (h) 10.48 ± 0.77 10.44 ± 0.07 10.52 ± 0.08 0.478 10.76 ± 0.68 9.92 ± 0.68c 10.76 ± 0.61 < 0.001
 Nap duration (h)a 0.97 (0.80, 1.24) 0.86 (0.77, 1.13) 1.07 (0.90, 1.41) 0.008 0.94 (0.77, 1.22) 1.03 (0.83, 1.33) 0.89 (0.81, 1.02) 0.367
Week
 Bedtime (hh:mm) 20:02 (19:29, 21:01) 20:13 (19:37, 21:11) 19:54 (19:19, 20:53) 0.049 19:40 (19:10, 20:06) 21:18 (20:59, 21:41)c 19:49 (19:29, 20:13) < 0.001
 Wake-up time (hh:mm) 06:34 (06:11, 06:59) 06:37 (06:11, 07.11) 06:31 (06:11, 06:52) 0.268 06:17 (06:04, 06:34) 07:04 (06:40, 07:24)c 06:44 (06:23, 07:05) < 0.001
 Nocturnal time-in-bed (h) 10.39 ± 0.80 10.33 ± 0.07 10.45 ± 0.09 0.310 10.63 ± 0.68 9.81 ± 0.70c 10.90 ± 0.70 < 0.001
 Nap duration (h)a 1.00 (0.80, 1.30) 0.86 (0.77, 1.12) 1.11 (0.91, 1.48) 0.002 1.01 (0.79, 1.31) 1.03 (0.85, 1.45) 0.83 (0.74, 0.95) 0.182
Weekend
 Bedtime (hh:mm) 20:13 (19:30, 21:11) 20:19 (19:33, 21:14) 20:05 (19:26, 21:02) 0.350 20:21 (19:58, 20:49) 21:31 (20:55, 22:03)c 19:35 (19:13, 20:13) < 0.001
 Wake-up time (hh:mm) 06:59 (06:31, 07:32) 07:04 (06:30, 07:39) 06:58 (06:32, 07:23) 0.276 06.37 (06:17, 07:21) 07:41 (07:05, 07:59)c 06:46 (06:20, 07:10) < 0.001
 Nocturnal time-in-bed (h) 10.72 (10.04, 11.41) 10.57 (10.02, 11.44) 10.81 (10.05, 11.37) 0.995 10.32 (10.04, 10.88)b 10.10 (9.63, 10.58)c 11.14 (10.52, 11.54)b < 0.001
 Nap duration (h)a 0.90 ± 0.32 0.83 ± 0.34 0.99 ± 0.30 0.132 0.89 ± 0.30 0.85 ± 0.37 0.95 ± 0.30 0.644
  1. Data are presented as mean ± SD or median with interquartile range
  2. Significance was determined using independent t-tests, Mann Whitney-U, one-way ANOVA or Kruskal-Wallis ANOVA tests
  3. aSample size for naps: Average: n = 103, weekdays: n = 103 and weekend days: n = 40
  4. bPost hoc analyses indicate significant differences between two marked groups
  5. cPost hoc analyses indicate that marked group is significantly different to the other two groups. Significance was accepted at p < 0.05