. 2021 Mar 3;8(3):188. doi: 10.3390/children8030188

Table 3.

Sleeping duration and quality in boys and girls by age in the three cities.

Variable	Sex	Age	Seville	Reykjavik	Tartu
Sleep duration (minutes)	Boys	13 years	424 ± 59 ^A	456 ± 69	462 ± 48
		14 years	440 ± 66 ^C	441 ± 64 ^D	469 ± 46
		15 years	458 ± 60 *	452 ± 71	444 ± 44
		16 years	432 ± 60 $Φ$	452 ± 62	432 ± 58 *, $λ$
	Girls	13 years	448 ± 57	440 ± 54	432 ± 46
		14 years	459 ± 64	440 ± 61	436 ± 63
		15 years	457 ± 64	440 ± 55	440 ± 39
		16 years	433 ± 59	447 ± 55 ^D	411 ± 55
Sleep quality (index)	Boys	13 years	4.33 ± 2.54	3.86 ± 2.13	4.00 ± 2.52
		14 years	4.85 ± 3.07 ^A	3.69 ± 2.09	3.84 ± 2.12
		15 years	4.88 ± 2.70	3.96 ± 2.07	4.69 ± 2.32
		16 years	5.11 ± 2.71	4.42 ± 2.08	5.41 ± 1.84 *, $λ$
	Girls	13 years	4.60 ± 2.66	4.38 ± 2.23	4.55 ± 2.26
		14 years	5.04 ± 2.57	4.51 ± 2.33	4.21 ± 1.84
		15 years	5.74 ± 3.024 *^{, A}	4.40 ± 1.75	4.85 ± 2.27
		16 years	6.46 ± 3.37 *, $λ$	5.66 ± 3.26	6.38 ± 2.36 *, $λ, Φ$

^A Significance of the difference between Sevilla vs. Reykjavik and Tartu; ^C Significance of the difference between Sevilla and Tartu; ^D Significance of the difference between Reykjavik and Tartu; * Statistical difference for 13 years; λ Statistical difference for 14 years; $Φ$ Statistical difference for 15 years.