Inverse L-Shaped Association Between Body Mass Index and Myopia in Chinese Schoolchildren: A Pilot Study

Figures & data

Table 1 Baseline Characteristics of the Participants

Characteristics	All participants	With Myopia		P-value
		Yes	No
No.	3658	2116	1542
Sex, n (%)				0.001
Female	1817 (49.7)	1102 (52.1)	715 (46.4)
Male	1841 (50.3)	1014 (47.9)	827 (53.6)
BMI (kg/m^2), Mean ± SD	19.8 ± 4.0	20.8 ± 4.1	18.5 ± 3.6	< 0.001
AL (mm), Mean ± SD	23.9 ± 1.3	24.5 ± 1.3	23.0 ± 0.8	< 0.001
SE (D), Mean ± SD	−1.6 ± 2.3	−3.0 ± 2.1	0.2 ± 0.6	< 0.001
Weekdays study time (hours), (IQR)	150.0 (110.0, 210.0)	180.0 (120.0, 240.0)	120.0 (90.0, 180.0)	< 0.001
Weekend study time (hours), (IQR)	180.0 (120.0, 280.0)	210.0 (120.0, 300.0)	150.0 (90.5, 237.5)	< 0.001
Weekdays outdoor time (hours), (IQR)	30.0 (20.0, 60.0)	35.0 (20.0, 60.0)	30.0 (20.0, 60.0)	< 0.001
Weekend outdoor time (hours), (IQR)	90.0 (60.0, 120.0)	60.0 (60.0, 120.0)	120.0 (60.0, 120.0)	< 0.001

Abbreviations: BMI, body mass index; AL, axial length; SE, spherical equivalent; D, diopters.

Table 2 Association Between BMI and Myopia in Multivariate Logistic Regression

BMI	Total (n)	Event (%)	Crude OR (95% CI)	Adjusted OR (95% CI)
				Model 1	Model 2
BMI, kg/m^2	3658	2116 (57.8)	1.18 (1.16~1.20)	1.19 (1.16–1.21)	1.14 (1.12–1.17)
BMI group
Q1	3269	1820 (55.7)	1 (Reference)	1 (Reference)	1 (Reference)
Q2	307	232 (75.6)	2.46 (1.88–3.22)	2.59 (1.97–3.39)	2.15 (1.62–2.86)
Q3	82	64 (78)	2.83 (1.67–4.8)	2.9 (1.74–5.01)	2.39 (1.37–4.18)

Notes: Model 1 was adjusted for sex. Model 2 was adjusted for sex, time spent studying on weekdays, time spent studying on weekends, time spent outdoors on weekdays, and time spent outdoors on weekends. BMI group: Q1 (less than 25 kg/m²); Q2: (25.0–29.9 kg/m²); Q3: (30.0 kg/m² or more).

Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index.

Figure 1 Association between BMI and myopia.

Table 3 Threshold Effect Analysis of the Relationship Between BMI and Myopia

Threshold of BMI, kg/m^2	OR	95% CI	P-value
<25	1.244	1.211–1.277	<0.001
≥25	1.063	0.964–1.171	0.219
Nonlinear test			0.004

Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index.

Figure 2 Association between BMI and myopia odds ratio. Solid and dashed lines represent the predicted value and 95% confidence intervals. Only 99% of the data are shown.