Table 1 Baseline Characteristics according to Age of Puberty from Hong Kong’s “Children of 1997” Birth Cohort. (Available case Analysis).
From: Age of puberty and Sleep duration: Observational and Mendelian randomization study
Characteristic | Classification | n | Onset of Breast/Genitalia Mean (SD), y | P value | n | Onset of Pubic Hair Development Mean (SD), y | P value | n | Age of Menarche/Voice breaking, Mean (SD), y | P value |
|---|---|---|---|---|---|---|---|---|---|---|
Gender | <0.01 | <0.01 | <0.01 | |||||||
Boys | 1921 | 10.88 (1.08) | 1428 | 11.48 (1.09) | 1781 | 13.08 (1.18) | ||||
Girls | 2961 | 9.60 (1.28) | 1736 | 10.56 (1.03) | 3177 | 11.94 (1.08) | ||||
Parents’ birthplace | <0.01 | <0.01 | 0.109 | |||||||
Both parents migrant | 1156 | 10.00 (1.33) | 716 | 10.86 (1.07) | 1244 | 12.37 (1.26) | ||||
One parent migrant | 980 | 10.03 (1.42) | 638 | 10.90 (1.16) | 1055 | 12.30 (1.23) | ||||
Both parents Hong Kong | 2608 | 10.18 (1.34) | 1717 | 11.06 (1.17) | 2555 | 12.39 (1.25) | ||||
Highest parental occupation | <0.01 | 0.02 | <0.01 | |||||||
I (professional) | 1046 | 10.2 (1.38) | 691 | 11.06 (1.20) | 1089 | 12.45 (1.26) | ||||
II (managerial) | 625 | 10.05 (1.30) | 403 | 11.00 (1.14) | 639 | 12.33 (1.24) | ||||
IIINM (nonmanual skilled) | 1298 | 10.14 (1.39) | 855 | 10.97 (1.16) | 1262 | 12.34 (1.21) | ||||
IIIM (manual skilled) | 700 | 10.03 (1.36) | 454 | 10.94 (1.11) | 748 | 12.35 (1.26) | ||||
IV (semi-skilled) | 404 | 9.96 (1.28) | 261 | 10.87 (1.17) | 420 | 12.26 (1.22) | ||||
V (unskilled) | 155 | 9.95 (1.30) | 99 | 10.98 (1.08) | 141 | 12.29 (1.30) | ||||
Household income per head in quintiles | 0.04 | 0.01 | 0.03 | |||||||
1st quintile (HK$ 1751 ± 413) | 806 | 10.03 (1.38) | 519 | 10.87 (1.11) | 835 | 12.26 (1.23) | ||||
2nd quintile (HK$ 2856 ± 325) | 899 | 10.09 (1.40) | 570 | 10.92 (1.21) | 868 | 12.34 (1.27) | ||||
3rd quintile (HK$ 4362 ± 556) | 845 | 10.06 (1.33) | 555 | 10.99 (1.12) | 897 | 12.38 (1.22) | ||||
4th quintile (HK$ 6822 ± 886) | 901 | 10.16 (1.35) | 616 | 11.06 (1.14) | 892 | 12.36 (1.24) | ||||
5th quintile (HK$ 14850 ± 16050) | 900 | 10.21 (1.34) | 564 | 11.07 (1.22) | 908 | 12.45 (1.23) | ||||
Highest parental education level | <0.01 | <0.01 | <0.01 | |||||||
Grade 9 or below | 1415 | 10.02 (1.37) | 894 | 10.90 (1.12) | 1457 | 12.25 (1.25) | ||||
Grade 10–11 | 2115 | 10.12 (1.35) | 1397 | 10.96 (1.13) | 2121 | 12.40 (1.25) | ||||
Grade 12 or above | 1286 | 10.17 (1.37) | 831 | 11.08 (1.21) | 1333 | 12.41 (1.23) | ||||
