| 0 - 2 years (parents’ report) | both genders | boys | girls | gender difference | |||
| n | % | n | % | n | % | ||
| sleep problems in general | 514/2275 | 22.6% | 259/1172 | 22.1% | 255/1103 | 23.1% | χ² = 0.338, p = 0.561 |
| difficulties falling asleep | 198/2275 | 8.7% | 95/1172 | 8.1% | 103/1103 | 9.3% | χ² = 1.086, p = 0.297 |
| difficulties sleeping through the night | 398/2275 | 17.5% | 205/1172 | 17.5% | 193/1103 | 17.5% | χ² = 0.000, p = 0.997 |
| difficulties falling asleep and difficulties sleeping through the night | 103/2275 | 4.5% | 51/1172 | 4.4% | 52/1103 | 4.7% | χ² = 0.173, p = 0.677 |
| 3 - 6 years (parents’ report) | |||||||
| sleep problems in general | 563/3528 | 16.0% | 272/1819 | 15.0% | 291/1709 | 17.0% | χ² = 2.827, p = 0.093 |
| difficulties falling asleep | 317/3529 | 9.0% | 157/1819 | 8.6% | 160/1710 | 9.4% | χ² = 0.568, p = 0.451 |
| difficulties sleeping through the night | 330/3529 | 9.4% | 154/1819 | 8.5% | 176/1710 | 10.3% | χ² = 3.468, p = 0.063 |
| difficulties falling asleep and difficulties sleeping through the night | 96/3528 | 2.7% | 45/1819 | 2.5% | 51/1709 | 3.0% | χ² = 0.867, p = 0.352 |
| 7 - 10 years (parents’ report) | |||||||
| sleep problems in general | 607/3698 | 16.4% | 321/1898 | 16.9% | 286/1800 | 15.9% | χ² = 0.706, p = 0.401 |
| difficulties falling asleep | 502/3699 | 13.6% | 258/1899 | 13.6% | 244/1800 | 13.6% | χ² = 0.001, p = 0.978 |
| difficulties sleeping through the night | 182/3699 | 4.9% | 100/1899 | 5.3% | 82/1800 | 4.6% | χ² = 0.997, p = 0.318 |
| difficulties falling asleep and difficulties sleeping through the night | 101/3699 | 2.7% | 52/1899 | 2.7% | 49/1800 | 2.7% | χ² = 0.001, p = 0.976 |
| 11 - 13 years (self report) | |||||||
| sleep problems in general | 695/3009 | 23.1% | 332/1535 | 21.6% | 363/1474 | 24.6% | χ² = 3.805, p = 0.051 |
| difficulties falling asleep | 513/3009 | 17.0% | 243/1535 | 15.8% | 20/1474 | 18.3% | χ² = 3.288, p = 0.070 |
| difficulties sleeping through the night | 234/3009 | 7.8% | 110/1535 | 7.2% | 124/1474 | 8.4% | χ² = 1.629, p = 0.202 |
| difficulties falling asleep and difficulties sleeping through the night | 66/3009 | 2.2% | 27/1535 | 1.8% | 39/1474 | 2.6% | χ² = 2.757, p = 0.097 |
| 14 - 17 years (self report) | |||||||
| sleep problems in general | 948/4590 | 20.7% | 393/2353 | 16.7% | 555/2237 | 24.8% | χ² = 46.002, p = 0.000 |
| difficulties falling asleep | 693/4591 | 15.1% | 300/2354 | 12.7% | 393/2237 | 17.6% | χ² = 20.826, p = 0.000 |
| difficulties sleeping through the night | 365/4591 | 8.0% | 120/2234 | 5.1% | 245/2237 | 11.0% | χ² = 53.719, p = 0.000 |
| difficulties falling asleep and difficulties sleeping through the night | 146/4590 | 3.2% | 39/2353 | 1.7% | 107/2237 | 4.8% | χ² = 36.381, p = 0.000 |