Participant characteristics are summarised in Table 1. In the univariable analysis, BMI was not found to be associated with any of the three outcome measures therefore we examined the associations of height and weight, but not BMI, in each of the multivariable analyses. Univariate analysis found females had a reduced teenage AXL (-0.499 mm; 95% CI: -0.583,-0.415) and steeper corneas (RCC) (-0.100 mm; 95% CI: -0.125,-0.075) compared to males, however no interactions were identified.
Table 1. Characteristics of participants (mothers and children).
Mother
|
|
Age (years)
Height (cm)
Weight (kg)
|
29.37 (4.4)
164.24(6.4)
62.19 (10.8)
|
Mother’s education
CCE/vocational
O level
A-level
Degree equivalent
|
272 (16.9)
570 (35.3)
466 (28.9)
305 (18.9)
|
Social Class*
I
II
III non-manual
III manual
IV/V
|
300 (18.6)
526 (32.2)
606 (37.6)
77 (4.8)
104 (6.5)
|
Child
|
|
Gender
Male
Female
|
748 (46.4%)
865 (53.6%)
|
Gestational age at birth
(weeks)
|
39.60 (1.6)
|
Birth weight (g)
|
3445.05 (508.5)
|
Breast Fed
No
Yes
|
212 (13.1%)
1401 (86.9%)
|
Myopia at 15 years
(average MSE ≤ 0.50 D)
|
|
No
|
1355 (84.0%)
|
Yes
|
258 (16.0%)
|
Values are numbers (%) or mean (SD)a
Family social class is defined as the highest household reported occupation, ranging from I (professional), II,III (subdivided manual and non-manual) IV, and V.
Life Stage: Prenatal (Table 2)
The factors found to be significant in univariable analysis and included in the multivariable prenatal life stage model were: maternal age at conception (years), maternal height (cm), pre-natal weight (kg), maternal education level, and parental socio-economic status.
No prenatal association was found between maternal height or weight with MSE. Maternal height was positively associated with a longer teenage AXL (0.010 mm; 95% CI: 0.003, 0.017) and greater RCC (0.005 mm; 95% CI: 0.003, 0.007), increased maternal weight was also associated with an increase in AXL (0.004 mm; 95% CI: 0.0001, 0.008). (Table 2)
Table 2. Associations between prenatal (maternal) factors and refractive error mean spherical equivalent (MSE in dioptres), axial length (AXL in mm) and radius of corneal curvature (RCC in mm) measured at age 15 years.
|
Multivariable analysis
|
P value
|
Mean Spherical Equivalent
|
(ß coefficient (95% CI))
|
|
Maternal weight (kg)
|
0.001 (-0.003,0.005)
|
p=0.530
|
Maternal height (cm)
|
0.0002 (-0.006,0.006)
|
p=0.050
|
Axial length
|
|
|
Maternal weight (kg)
|
0.004 (0.0001,0.008)
|
p=0.042
|
Maternal height (cm)
|
0.010 (0.003,0.017)
|
p=0.006
|
Corneal Curvature
|
|
|
Maternal weight (kg)
|
0.0004 (-0.0009,0.002)
|
P=0.553
|
Maternal height (cm)
|
0.005 (0.003,0.007)
|
p<0.001
|
Life Stage: Birth (Table 3)
The multivariable model of the birth life stage included gestational age (weeks), birth weight (g), and length at birth (cm). No association was found between birth length or weight with MSE. Birth length was associated with an increase in teenage AXL (0.067 mm; 95% CI: 0.032, 0.10) and flatter RCC (0.023 mm; 95% CI: 0.013, 0.034) respectively. An increase in birth weight was also associated with flatter RCC (0.005 mm; 95% CI: 0.0003, 0.009).
Table3. Associations between birth factors and refractive error mean spherical equivalent (MSE dioptres), axial length (AXL mm) and radius of corneal curvature (RCC mm) measured at age 15 years.
|
Multivariable analysis
|
P value
|
Mean Spherical Equivalent
|
(ß coefficient (95% CI))
|
|
Birth weight (per 100g)
|
0.002 (-0.011,0.014)
|
p=0.793
|
Birth length (cm)
|
-0.025 (-0.056,0.007)
|
p=0.125
|
Axial length
|
|
|
Birth weight (per 100g)
|
0.006 (-0.008,0.021)
|
p=0.381
|
Birth length (cm)
|
0.067 (0.032,0.102)
|
p<0.001
|
Corneal Curvature
|
|
|
Birth weight (per 100g)
|
0.005 (0.0003,0.009)
|
p=0.035
|
Birth length (cm)
|
0.023 (0.013,0.034)
|
p<0.001
|
Life Stage: Teenage (15 years) (Table 4)
Factors included in the teenage life stage model included weight (kg) and height (cm) at 15 years of age. An increase in teenage height was associated with a reduction in MSE (-0.007 D; 95% CI: -0.013, -0.001), an increase in AXL (0.021 mm; 95% CI: 0.015, 0.028) and flatter RCC (0.008 mm; 95% CI: 0.006, 0.010). Weight at 15 years was also associated with an increase in AXL (0.005 mm; 95% CI: 0.001, 0.009)
Table4. Associations between teenage factors height and weight and refractive error mean spherical equivalent (MSE dioptres), axial length (AXL mm) and radius of corneal curvature (RCC mm) measured at age 15 years.
|
Multivariable analysis
|
P value
|
Mean Spherical Equivalent
|
(ß coefficient (95% CI))
|
|
Teenage Weight (kg)
|
0.002 (-0.0015,0.006)
|
p=0.254
|
Teenage Height (cm)
|
-0.007 (-0.013,-0.001)
|
p=0.028
|
|
|
|
Axial length
|
|
|
Teenage Weight (kg)
|
0.005 (0.001,0.009)
|
p=0.023
|
Teenage Height (cm)
|
0.021(0.015,0.028)
|
p<0.001
|
|
|
|
Corneal Curvature
|
|
|
Teenage Weight (kg)
|
0.0002 (-0.001,0.001)
|
p=0.730
|
Teenage Height (cm)
|
0.008(0.006,0.010)
|
p<0.001
|