Risk Factors for Incident Myopia among Teenaged Students of the Experimental Class of the Air Force in China

Table 2

Univariate analysis of potential risk factors for incident myopia.

Risk factor	Incident myopia, % (n)	value (χ^2)
Parental myopia
0 parents	27.48 (119)	0.7525	0.1330
1 parent	23.68 (18)
2 parents	30.77 (4)
Outdoor activity time (per week)
≥14 h	17.72 (14)	0.0063	0.0020
≥9.33 h to <14 h	21.66 (34)
<9.33 h	32.52 (93)
Near-work time (per week)
≥28 h	30.62 (128)	0.0010	0.0005
≥21 h to <28 h	12.60 (9)
<21 h	12.00 (4)
Reading/writing distance
<30 cm	42.86 (27)	0.0065	—
≥30 cm	24.84 (114)
Continuous reading/writing for 1 h or more
Seldom or none	26.64 (69)	0.8499	—
Frequently	27.38 (72)
Age at the start of primary school
>6 years	25.64 (40)	0.6452	—
≤6 years	27.60 (101)
Sleep duration (per week)
≤49 h	28.57 (90)	0.3221	—
>49 h	24.64 (51)
Dietary bias
One or more	30.04 (67)	0.1777	—
None	24.75 (74)