Effect of Sunshine Duration on Myopia in Primary School Students from Northern and Southern China

Figures & data

Table 1 Characteristics of Demography in Different Grades of Students from 4 Cities

	Shenyang	Qingdao	Qingyuan	Fangchenggang
Number	2278	2262	2300	2331
Grade 1 (%)	375 (16.5)	376 (16.6)	377 (16.4)	382 (16.4)
Grade 2 (%)	399 (17.5)	373 (16.5)	402 (17.5)	375 (16.0)
Grade 3 (%)	399 (17.1)	396 (17.5)	400 (17.4)	414 (16.5)
Grade 4 (%)	377 (16.5)	373 (16.4)	375 (16.3)	373 (17.8)
Grade 5 (%)	362 (15.9)	370 (16.4)	354 (15.4)	376 (16.1)
Grade 6 (%)	376 (16.5)	374 (16.5)	392 (17.0)	411 (17.7)
Male (%)	1191 (52.3)	1202 (53.1)	1242 (54.0)	1276 (54.7)

Figure 1 Flowchart showing the process of screening participants.

Table 2 Sample Characteristics and Myopia Prevalence Among Schoolchildren in Different Regions

	Shenyang	Qingdao	Qingyuan	Fangchenggang
Annual Sunshine duration (h)	2495	2075	1632	1896
Annual Temperature (°C)	9	14	21.1	28.4
Altitude (m)	50	77	32	15
Latitude (degree)	41°48ʹ N	36°06ʹ N	24°49ʹ N	21°45ʹ N
Longitude (degree)	123°23ʹ E	120°19ʹ E	112°29ʹ E	108°21ʹ E
Myopia prevalence (%)	24.5	26.4	28.1	31.3

Figure 2 Distribution of myopia between north and south school children by Grades.

Figure 3 Distribution of spherical equivalent refractive error in different regions by grades. Error bars show SDs.

Table 3 Myopia Severity Category by Gender, Grades, Average Annual Sunshine Duration, and Temperature

Risk Factors	Low Myopia		Moderate Myopia		High Myopia		All
	Prevalence, %	95% CI	Prevalence, %	95% CI	Prevalence, %	95% CI	Prevalence, %	95% CI
Gender
Boys	21.0	19.4–22.6	5.0	4.2–5.9	0.5	0.3–0.9	26.5	24.7–28.3	c^2 = 6.2, P = 0.013
Girls	23.7	21.9–25.6	5.6	4.6–6.6	0.5	0.2–0.9	29.8	27.8–31.8
Grades
1	7.30	5.5–9.4	0.30	0.0–1.0	0.0	0.0–0.5	7.5	5.8–9.7	c^2 = 559.5, P < 0.001
2	12.10	9.9–14.7	0.90	0.4–1.9	0.1	0.0–0.7	13.2	10.9–15.8
3	19.00	16.3–21.9	2.30	1.3–3.5	0.1	0.0–0.7	21.4	18.6–24.4
4	26.60	23.5–29.9	4.80	3.4–6.6	0.0	0.0–0.5	31.4	28.1–34.9
5	33.90	30.5–37.5	10.00	7.9–12.4	0.7	0.2–1.6	44.6	41.0–48.3
6	35.00	31.7–38.5	13.60	11.3–16.3	1.9	1.1–3.2	50.6	47.0–54.2
Annual sunshine duration (hours)
1500–1900	24.00	22.3–25.8	5.10	4.2–6.0	0.6	0.4–1.1	29.7	27.9–31.6	c^2 = 8.0, P = 0.018
1900–2300	21.40	19.1–23.9	5.40	4.2–6.9	0.4	0.1–1.0	27.3	24.7–30.0
2300	19.50	17.2–21.9	5.60	4.3–7.1	0.2	0.0–0.6	25.2	22.7–27.8
Annual temperature (°C)
5–15	20.40	18.8–22.2	5.50	4.6–6.5	0.3	0.1–0.6	26.3	24.5–28.1	c^2 = 9.7, P = 0.008
15–25	24.30	21.8–26.8	3.20	2.3–4.4	0.6	0.2–1.3	28.1	25.5–30.8
25	23.80	21.3–26.3	6.90	5.5–8.5	0.7	0.3–1.3	31.3	28.6–34.1

Note: P value was calculated using the Pearson Chi-squared tests, comparing the total prevalence among groups.

Table 4 Logistic Regression Analysis for Myopia, with Gender, Grade, Annual Sunshine Duration and Temperature as Risk Factors

Risk Factors	Univariate Analysis				Multiple Analysis
	β	OR	95% CI	P value	β	OR	95% CI	P value
Gender
Boys		1				1
Girls	0.163	1.178	1.035–1.340	0.013	0.189	1.208	1.052–1.387	0.007
Grade	0.5	1.649	1.578–1.724	<0.001	0.502	1.652	1.580–1.726	<0.001
1
2
3
4
5
6
Annual sunshine duration (hours)
1500–1900		1				1
1900–2300	−0.118	0.889	0.759–1.041	0.143	−0.202	0.817	0.674–0.991	0.04
2300	−0.227	0.797	0.679–0.937	0.006	−0.327	0.721	0.593–0.877	0.001
Annual temperature (°C)
5–15		1				1
15–25	0.093	1.097	0.936–1.286	0.254	−0.157	0.854	0.706–1.035	0.107
25	0.247	1.28	1.096–1.495	0.002

Note: Significance P value < 0.05.

Abbreviations: CI, confidence interval; OR, odds ratio.