Genetic confounding in the association of early motor development with childhood and adolescent exercise behavior

Table 1 Means, standard deviations (SD) of early motor development and later exercise behavior traits

Traits	Total		MZM		DZM		MZF		DZF		DOS
Traits	Mean (SD)	N	Mean (SD)	N	Mean (SD)	N	Mean (SD)	N	Mean (SD)	N	Mean (SD)	N
MD-FS	0.00 (1.00)	20,911	0.0 (1.0)	3510	0.0 (1.0)	3527	0.0 (1.0)	3724	−0.1 (1.0)	3258	0.0 (1.0)	6874
GM5	0.55 (0.98)	17,189	0.6 (1.0)	2914	0.6 (1.0)	2900	0.4 (0.8)	3161	0.4 (0.9)	2687	0.6 (1.1)	5527
MET7	733 (665)	3632	871 (800)	675	871 (800)	665	536 (514)	618	510 (507)	526	799 (659)	1148
MET10	1120 (867)	3735	1274 (885)	691	1274 (885)	672	824 (679)	651	818 (714)	525	1205 (870)	1196
MET12	1322 (1068)	7043	1104 (1584)	1269	1567 (1104)	1153	944 (863)	1314	947 (860)	1040	1466 (1104)	2267
MET14	1420 (1265)	3990	1261 (1584)	612	1712 (1261)	520	1072 (1009)	915	1134 (1064)	705	1610 (1409)	1238

Note The total column depicts the mean/SD across all twin pairs, whereas ensuing columns stratify results per zygosity: MZM, monozygotic male twins; DZM, dizygotic male twins; MZF, monozygotic female twins; DZF, dizygotic female twins; DOS, dizygotic opposite-sex twins. N is the number of complete twin pairs, i.e. pairs without missing data in either twin or co-twin. MD-FS, the factor score of motor development before age 2; GM5, gross motor development at age 5; MET7, MET10, MET12, and MET14 represent the exercise behavior at each age (7, 10, 12, and 14 years)

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