Table 1.

Characteristics of the study subjects (N = 1488).

Variables	Total, n (%)	Case, n (%)	Control, n (%)	P*
Total	1488 (100)	494 (100)	994 (100)	NA
Age (year, mean (SD))	13.6 (1.8)	13.6 (1.8)	13.6 (1.8)	0.941
Gender
Boys	420 (28.2)	140 (28.3)	280 (28.2)	0.945
Girls	1068 (71.8)	354 (71.7)	714 (71.8)
Body height (m, mean (SD))	1.62 (0.1)	1.62 (0.1)	1.61 (0.1)	0.106
Body weight (kg, mean (SD))	50.47 (11.5)	48.32 (9.3)	51.55 (12.3)	<0.001
BMI (kg/m2, mean (SD))	19.2 (3.3)	18.2 (2.7)	19.6 (3.5)	<0.001
Ethnicity
Han	1406 (96.4)	475 (96.7)	931 (96.2)	0.587
Minorities	53 (3.6)	16 (3.3)	37 (3.8)
Missing data	29	NA	NA
Myopia
No	425 (28.7)	128 (26.0)	297 (30.1)	0.098
Yes	1055 (71.3)	365 (74.0)	690 (69.9)
Missing data	8	NA	NA
Family history of scoliosis
No	1355 (91.2)	431 (87.2)	924 (93.1)	<0.001
Yes	131 (8.8)	63 (12.8)	68 (6.9)
Missing data	2	NA	NA
Education level of father
Secondary school	236 (16.0)	72 (14.6)	164 (16.7)	0.005
High school	318 (21.5)	103 (20.9)	215 (21.9)
College/University	724 (49.0)	270 (54.7)	454 (46.2)
Unknown	199 (13.4)	49 (9.9)	150 (15.3)
Missing data	11	NA	NA
Education level of mother
Secondary school	284 (19.2)	92 (18.7)	192 (19.4)	<0.001
High school	370 (25.0)	105 (21.3)	71.6 (26.8)
College/University	630 (42.5)	255 (51.7)	375 (38.0)
Unknown	197 (13.3)	41 (8.3)	156 (15.8)
Missing data	7	NA	NA
Academic pressure
Above average	37 (2.5)	14 (2.9)	23 (2.3)	0.288
Average	1137 (77.0)	364 (74.6)	772 (78.2)
Below average	302 (20.5)	110 (22.5)	192 (19.5)
Missing Data	12	NA	NA
Dairy products intake
No	116 (7.8)	51 (10.3)	65 (6.6)	0.010
Yes	1368 (92.2)	442 (89.7)	926 (93.4)
Missing data	4	NA	NA
MVPA time (min/week, mean (SD))	50 (77.1)	37.1 (48.7)	56.3 (86.9)	<0.001

NA, not applicable or no data available.

Abbreviations: BMI, body mass index.