From January 2017 to December 2019, a total of 383 children (age < 3 years) were admitted to the Qingdao Eye Hospital (1 person had normal high intraocular pressure and was included in the normal child group), and family history of eye diseases was excluded from the study. Together with these children, we evaluated 159 siblings for a total of 541 children from 383 separate families. Among them, there were 229 single-child families and 154 multiple-child families (about 1.5:1).
The incidence of ophthalmic diseases was here found to vary with parity. The prevalence of ophthalmic diseases was 62.2% (239/384) in the oldest child, 90.8% (139/153) in the second child, and 100% (4/4) in the third.
The mother’s age at childbirth for the affected children was 27.1 ± 5.3 years, and the mother’s age at childbirth was 26.7 ± 3.7 years for unaffected children (p = 0.322). The father’s age at childbirth was 28.3 ± 5.6 years for unaffected children and 27.8 ± 4.0 years for affected children (p = 0.251).
The mother’s average highest level of education was 3.9 ± 1.3 among affected children and 4.3 ± 1.6 for unaffected children (p = 0.008). The father’s highest level of education was 4.1 ± 1.3 for affected children and 4.4 ± 1.5 for unaffected children (p = 0.023). Whether the child was born prematurely was also found to differ statistically significantly between the affected and unaffected children (p = 0.031). The child’s sex, birth weight, caesarian vs vaginal delivery, and whether the mother was sick or took medicine during pregnancy showed no statistically significant difference between the affected and unaffected children (p > 0.05).
Table 1
Characteristics of the Study Population
| | Number | Average | Standard deviation | 95% CI | Min | Max |
Birth weight | Unaffected | 159 | 3.4 | 0.4 | 3.3–3.4 | 2.5 | 4.5 |
Affected | 382 | 3.4 | 0.5 | 3.3–3.4 | 1 | 4.5 |
Total | 541 | 3.4 | 0.5 | 3.3–3.4 | 1 | 4.5 |
mother's age at childbirth | Unaffected | 159 | 26.7 | 3.7 | 26.1–27.2 | 20 | 45 |
Affected | 382 | 27.1 | 5.3 | 26.6–27.6 | 20 | 48 |
Total | 541 | 27.0 | 4.9 | 26.6–27.4 | 20 | 48 |
mother's highest level of education | Unaffected | 159 | 4.3 | 1.6 | 4.0-4.5 | 2 | 8 |
Affected | 382 | 3.9 | 1.3 | 3.8-4.0 | 2 | 8 |
Total | 541 | 4.0 | 1.4 | 3.9–4.1 | 2 | 8 |
father's age at childbirth | Unaffected | 159 | 27.8 | 4.0 | 27.1–28.4 | 20 | 46 |
Affected | 382 | 28.3 | 5.6 | 27.8–28.9 | 20 | 50 |
Total | 541 | 28.2 | 5.2 | 27.7–28.6 | 20 | 50 |
father's highest level of education | Unaffected | 159 | 4.4 | 1.5 | 4.2–4.6 | 2 | 7 |
Affected | 382 | 4.1 | 1.3 | 4.0-4.2 | 2 | 7 |
Total | 541 | 4.2 | 1.3 | 4.1–4.3 | 2 | 7 |
Binary regression analysis showed parity to be related to whether the child had eye disease (OR = 7.392 [4.030–13.559], p < 0.001). The same was true for both the mother’s (OR = 0.807 [0.658–0.990], p = 0.008) and father’s highest level of education (OR = 0.935 [0.756–1.156], p = 0.023). Preterm birth (p = 0.999) and whether the mother was sick or took medication during pregnancy was found not to be related to whether the child had ophthalmic diseases (p = 0.13).
Table 2
Characteristics of the Multi-child families
| | Number | Average | Standard deviation | 95% CI | Min | Max |
Birth weight | Unaffected | 159 | 3.4 | 0.4 | 3.3–3.4 | 2.5 | 4.5 |
Affected | 153 | 3.4 | 0.5 | 3.4–3.5 | 1.5 | 4.5 |
Total | 312 | 3.4 | 0.4 | 3.4–3.4 | 1.5 | 4.5 |
mother's age at childbirth | Unaffected | 159 | 26.7 | 3.7 | 26.1–27.2 | 20 | 45 |
Affected | 153 | 32.0 | 4.6 | 31.2–32.7 | 20 | 48 |
Total | 312 | 29.3 | 4.9 | 28.7–29.8 | 20 | 48 |
father's age at childbirth | Unaffected | 159 | 27.8 | 4.0 | 27.1–28.4 | 20 | 46 |
Affected | 153 | 33.3 | 5.0 | 32.5–34.1 | 22 | 50 |
Total | 312 | 30.5 | 5.3 | 29.9–31.1 | 20 | 50 |
In multi-child families, the prevalence of ophthalmic diseases was 6.5% in the first child (10/155), 90.8% in the second child (139/153), and 100% in the third child (4/4).
In multi-child families, the mother’s age at childbirth was 32.0 ± 4.6 years for affected children, averaged across all families and all affected children, while the mother’s age at normal childbirth was 26.7 ± 3.7 years (p < 0.001). The father’s age at childbirth was 33.3 ± 5.0 years, while the father’s age at the birth of an unaffected child was 27.8 ± 4.0 years (p < 0.001). There were statistically significant differences in whether the child was born prematurely (p = 0.012), whether the mother was sick during pregnancy, or if she took medication (p = 0.027) between the affected and unaffected groups.
The average age difference between the second child and the first child was 6.1 ± 3.7 years (1–18 years), and the difference in birth weight was 38 ± 370 g (-1700–1700 g).