Table 2.
Univariable linear mixed-effects model estimates of monthly changes in height and height SDS from 1.5 to 3 years of age according to sleep characteristics, demographic characteristics, and socioeconomic factors.
| Univariable model | Height B (×10−3 cm/month) |
p-value | Height SDS B (×10−3 SD/month) |
p-value |
|---|---|---|---|---|
| Sleep duration (≥ 10 h vs. < 10 h) |
5.10 (2.28, 7.92) | <0.001 | 0.41 (−0.32, 1.13) | 0.274 |
| Sleep duration (hrs) | 3.86 (2.39, 5.34) | <0.001 | 0.43 (0.05, 0.81) | 0.026 |
| Bedtime (20:00–21:59 vs. ≥ 22:00) |
7.57 (4.12, 11.02) | <0.001 | 2.48 (1.59, 3.37) | <0.001 |
| Nighttime awakenings (< 3 vs. ≥ 3) |
8.31 (−1.47, 18.09) | 0.096 | 3.01 (0.48, 5.53) | 0.020 |
| Sex (male vs. female) | −13.10 (−15.74, −10.37) | <0.001 | −3.56 (−4.25, −2.86) | <0.001 |
| Maternal height SDS | 17.16 (15.80, 18.53) | <0.001 | 2.29 (1.94, 2.65) | <0.001 |
| Paternal height SDS | 17.00 (15.60, 18.40) | <0.001 | 2.49 (2.13, 2.85) | <0.001 |
| Maternal education status (post-secondary education vs. ≤ senior high school) | 5.99 (3.08, 8.89) | <0.001 | 3.56 (2.81, 4.31) | <0.001 |
| Paternal education status (post-secondary education vs. ≤ senior high school) | 1.87 (−0.88, 4.62) | 0.183 | 1.67 (0.95, 2.38) | <0.001 |
| Annual household income (≥ 6 million yen vs. < 6 million yen) | 2.64 (−0.40, 5.69) | 0.089 | 2.26 (1.47, 3.04) | <0.001 |
| Worker (multi-earner households vs. single-earner households) | 3.28 (0.49, 6.06) | 0.021 | 3.92 (3.20, 4.64) | <0.001 |
B, regression coefficient; CI, confidence interval; SDS, standard deviation score. Values are presented as B (95% CI). Estimates represent the monthly change in height or height SDS. For categorical variables, estimates represent the difference between the indicated group and the reference group, with comparisons shown as [target group] vs. [reference group]. For continuous variables, estimates represent the change per unit increase in the variable.