Table 2. Effect of single modifiable factors on myopia incidence.

Variables	Total			1–6 grades			7–11 grades
	PR (95% CI)	P		PR (95% CI)	P		PR (95% CI)	P
Note: The model adjusted sex, residence (urban or rural), grade, parents’ myopia status (0 or 1 or 2 parents with myopia), and the cluster effect of the PLAD. Abbreviation: PR=prevalence ratio; CI=confidence interval; PLAD=provincial-level administrative division.
Outdoor time
0	Ref			Ref			Ref
1	0.92 (0.78, 1.08)	0.315		0.93 (0.77, 1.12)	0.434		0.90 (0.64, 1.26)	0.530
Eye exercises
0	Ref			Ref			Ref
1	0.96 (0.80, 1.14)	0.611		1.00 (0.81, 1.22)	0.974		0.82 (0.57, 1.17)	0.272
Screen time
0	Ref			Ref			Ref
1	1.04 (0.84, 1.30)	0.697		0.92 (0.69, 1.23)	0.586		1.19 (0.86, 1.66)	0.297
Lying down watching/reading
0	Ref			Ref			Ref
1	0.96 (0.71, 1.30)	0.785		0.76 (0.50, 1.16)	0.205		1.17 (0.76, 1.80)	0.474
Watching screen in darkness
0	Ref			Ref			Ref
1	0.98 (0.66, 1.45)	0.911		0.69 (0.37, 1.29)	0.244		1.14 (0.69, 1.87)	0.607
Posture reminding
0	Ref			Ref			Ref
1	0.98 (0.83, 1.16)	0.845		0.95 (0.79, 1.14)	0.578		1.11 (0.78, 1.59)	0.558
Desktop brightness in sunny day
0	Ref			Ref			Ref
1	0.86 (0.73, 1.01)	0.070		0.91 (0.75, 1.11)	0.359		0.74 (0.55, 1.00)	0.050
Light brightness in the evening
0	Ref			Ref			Ref
1	1.15 (0.78, 1.70)	0.484		1.49 (0.85, 2.63)	0.164		0.79 (0.46, 1.34)	0.380
Seat/desk fitted for height
0	Ref			Ref			Ref
1	0.82 (0.65, 1.03)	0.092		0.89 (0.65, 1.22)	0.477		0.70 (0.49, 0.99)	0.044
Sleeping duration
0	Ref			Ref			Ref
1	0.90 (0.76, 1.07)	0.229		0.89 (0.74, 1.08)	0.227		0.94 (0.64, 1.38)	0.475
Sedentary time
0	Ref			Ref			Ref
1	0.93 (0.79, 1.10)	0.403		0.95 (0.79, 1.14)	0.579		0.87 (0.60, 1.26)	0.748