Table 4.
Comparison of sleep and sleep-related habits and activity between the “Nenne-meet” and “Nenne-not-meet” groups.
| Sleep Habits and Daytime Behavior | Nenne-meet (n = 752) | Nenne-not-meet (n = 1,372) | P a | P b | Effect Size r | ||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Median | Interquartile Range | Mean | Median | Interquartile Range | ||||
| Wake-up time | 7:09 am | 7:08 am | 6:48–7:33 am | 7:24 am | 7:19 am | 6:49–7:51 am | < .001 | < .001 | .12 |
| Irregularity of wake-up time (min) | 22.4 | 20.9 | 14.5–28.7 | 30.2 | 27.8 | 19.8–37.7 | < .001 | < .001 | .26 |
| Bedtime | 8:30 pm | 8:35 pm | 8:06–8:59 pm | 9:18 pm | 9:17 pm | 8:52–9:43 pm | < .001 | < .001 | .51 |
| Irregularity of bedtime (min) | 19.8 | 15.9 | 10.5–26.2 | 29.1 | 25.5 | 16.0–36.8 | < .001 | < .001 | .28 |
| Sleep-onset latency (min) | 19.5 | 17.9 | 8.6–27.1 | 23.1 | 20.0 | 11.4–30.7 | < .001 | < .001 | .10 |
| Irregularity of sleep-onset latency (min) | 10.6 | 9.9 | 7.0–14.1 | 13.5 | 11.3 | 8.7–16.8 | < .001 | < .001 | .13 |
| Nocturnal sleep duration | 10 h, 18 min | 10 h, 14 min | 9 h, 54 min–10 h, 39 min | 9 h, 39 min | 9 h, 36 min | 9 h, 12 min–10 h, 4 min | < .001 | < .001 | −.46 |
| Irregularity of nocturnal sleep duration (min) | 30.1 | 27.6 | 19.2–37.1 | 42.8 | 38.7 | 28.4–52.5 | < .001 | < .001 | .34 |
| Social jetlag (min) | 17.5 | 14.0 | 6.0–26.0 | 24.4 | 18.0 | 9.0–34.0 | < .001 | < .001 | .16 |
| Number of times awakening after sleep onset | 0.2 | 0.1 | 0–0.3 | 0.5 | 0.1 | 0–0.6 | < .001 | < .001 | .18 |
| Breastfeeding at night (%) | 4.4 | 0* | 0–0* | 25.0 | 0* | 0–50.0 | < .001 | < .001 | .26 |
| Nap start time | 1:02 pm | 1:00 pm | 12:24–1:39 pm | 1:14 pm | 1:04 pm | 12:33–1:52 pm | < .005 | < .001 | .07 |
| Irregularity of nap start time (min) | 52.7 | 48.3 | 27.5–74.9 | 59.7 | 53.7 | 32.2–81.8 | < .001 | < .001 | .09 |
| Nap end time | 2:48 pm | 2:49 pm | 2:14–3:23 pm | 3:13 pm | 3:04 pm | 2:34–3:49 pm | < .001 | < .001 | .17 |
| Irregularity of nap end time (min) | 55.3 | 51.2 | 27.5–76.8 | 63.3 | 59.5 | 32.2–88.5 | < .001 | < .001 | .10 |
| Nap duration | 1 h, 24 min | 1 h, 27 min | 1 h, 1 min–1 h, 49 min | 1 h, 37 min | 1 h, 41 min | 1 h, 14 min–2 h, 1 min | < .001 | < .001 | .17 |
| Irregularity of nap duration (min) | 31.4 | 29.8 | 19.8–42.0 | 35.9 | 34.3 | 22.8–46.5 | < .001 | < .005 | .11 |
| Total sleep duration | 11 h, 43 min | 11 h, 44 min | 11 h, 18 min–12 h, 5 min | 11 h, 17 min | 11 h, 17 min | 10 h, 52 min–11 h, 44 min | < .001 | < .001 | −.30 |
| Irregularity of total sleep duration (min) | 40.4 | 37.8 | 27.7–50.8 | 51.1 | 46.9 | 34.8–62.8 | < .001 | < .001 | .24 |
| TV-viewing time | 1 h, 52 min | 1 h, 43 min | 56 min–2 h, 28 min | 1 h, 53 min | 1 h, 39 min | 1 h–2 h, 34 min | .678 | .085 | .01 |
| End time of TV viewing | 7:39 pm | 7:50 pm | 6:56–8:30 pm | 8:32 pm | 8:43 pm | 7:45–9:20 pm | < .001 | < .001 | .34 |
| Smartphone-viewing time (min) | 9.13 | 0* | 0–7.0 | 17.8 | 1.0 | 0–17.0 | < .001 | < .005 | .12 |
| End time of smartphone viewing | 4:59 pm | 5:40 pm | 3:00–7:17 pm | 5:58 pm | 6:43 pm | 4:17–8:00 pm | < .001 | < .005 | .16 |
| Total media-viewing time | 2 h, 1 min | 1 h, 51 min | 1 h–2 h, 39 min | 2 h, 11 min | 1 h, 59 min | 1 h, 11 min–2 h, 50 min | < .05 | < .005 | .05 |
| End of total media-viewing time | 7:40 pm | 7:51 pm | 7:00–8:30 pm | 8:33 pm | 8:43 pm | 7:47–9:21 pm | < .001 | < .001 | .34 |
| Play outside for 30 minutes or more in the morning (%) | 32.7 | 29.0 | 14.0–57.0 | 27.1 | 14.0 | 0–43.0 | < .001 | .068 | −.11 |
| Dinner end time | 6:36 pm | 6:34 pm | 6:13–7:00 pm | 6:58 pm | 7:00 pm | 6:30–7:24 pm | < .001 | < .001 | .27 |
| Irregularity of dinner end time (min) | 22.2 | 21.0 | 13.6–28.8 | 26.7 | 25.0 | 16.0–34.7 | < .001 | < .001 | .15 |
| Bathing end time | 6:51 pm | 7:05 pm | 6:09–7:39 pm | 7:27 pm | 7:39 pm | 6:50–8:13 pm | < .001 | < .001 | .26 |
| Irregularity of bathing end time (min) | 29.8 | 22.5 | 13.6–39.3 | 36.0 | 28.7 | 17.3–49.0 | < .001 | < .001 | .14 |
| Time between bathing and bedtime | 1 h, 39 min | 1 h, 29 min | 57 min–2 h, 9 min | 1 h, 52 min | 1 h, 38 min | 1 h, 10 min–2 h, 23 min | < .001 | < .001 | .12 |
| Irregularity of time between bathing and bedtime (min) | 27.3 | 20.8 | 12.2–35.6 | 34.6 | 28.0 | 16.4–45.9 | < .001 | < .001 | .17 |
| Going out after 7:00 p.m. (%) | 3.5 | 0* | 0–0* | 7.7 | 0* | 0–14.0 | < .001 | < .001 | .18 |
| Caregiver wake-up time | 6:43 am | 6:45 am | 6:19–7:09 am | 6:49 am | 6:49 am | 6:16–7:19 am | < .05 | < .001 | .05 |
| Irregularity of caregiver wake-up time (min) | 29.2 | 25.7 | 16.9–38.2 | 36.6 | 32.3 | 20.9–47.0 | < .001 | < .001 | .17 |
| Caregiver bedtime | 10:43 pm | 10:45 pm | 9:43–11:36 pm | 10:58 pm | 10:54 pm | 10:04–11:44 pm | < .001 | < .005 | .08 |
| Irregularity of caregiver bedtime (min) | 43.2 | 36.4 | 20.0–59.5 | 43.9 | 37.8 | 22.7–57.6 | .260 | .969 | .02 |
| Caregiver sleep-onset latency (min) | 29.8 | 21.3 | 12.5–38.8 | 32.2 | 23.1 | 12.5–44.4 | .061 | < .05 | .04 |
| Irregularity of caregiver sleep-onset latency (min) | 14.9 | 10.8 | 6.6–20.2 | 15.9 | 11.3 | 6.6–22.3 | .242 | < .01 | .03 |
| Caregiver nocturnal sleep duration | 7 h, 29 min | 7 h, 31 min | 6 h, 46 min–8 h, 16 min | 7 h, 18 min | 7 h, 22 min | 6 h, 36 min–8 h, 5 min | < .005 | < .05 | −.07 |
| Irregularity of caregiver nocturnal sleep duration (min) | 52.9 | 48.0 | 32.2–68.9 | 56.8 | 51.5 | 35.7–71.4 | < .005 | < .05 | .07 |
| Caregiver social jetlag (min) | 27.3 | 19.0 | 9.0–38.0 | 32.7 | 25.0 | 11.0–47.0 | < .001 | < .005 | .09 |
The percentages of “Breastfeeding at night” were calculated from the population who answered “breastfeeding” in the demographic survey, and who answered “breastfed at night,” “breastfed before 30 minutes of bedtime,” or “breastfed in the bed” in daily question, n = 408. a Mann–Whitney U test. b Multiple regression analysis, adjusted for toddler’s age, nursery school attendance, number of siblings, mother’s age, father’s age, mother’s educational level, and mother’s employment status. * Most of the data were 0. TV = television.