Table 1. Demographic characteristics in participants with complete or incomplete information on potential confounders.
| Variable | Sample with incomplete information (N=63,842) | Sample with full information (N=25,278) | P-value |
|---|---|---|---|
| Age (years) a | 59.0 (7.2) | 51.7 (7.2) | <1.0E-99 |
| Birth weight (kg) a | 3.3 (0.7) | 3.4 (0.6) | 3.70E-07 |
| Townsend Deprivation Index (natural log) a | 2.0 (0.4) | 2.0 (0.4) | 7.60E-03 |
| Time spent outdoors currently (hours/day) a | 3.9 (2.3) | 3.4 (2.2) | <1.0E-99 |
| Age completed full time education (years) a,b | 16.6 (2.1) | 17.1 (2.0) | <1.0E-99 |
| Female gender | 33075 (51.8%) | 15104 (59.8%) | <1.0E-99 |
|
| |||
| Maternal age category c | 4.00E-14 | ||
| <20 | 383 (3.7%) | 888 (3.5%) | |
| 20-24 | 2842 (27.8%) | 7842 (31.0%) | |
| 25-29 | 3987 (38.9%) | 9894 (39.1%) | |
| 30-34 | 2149 (21.0%) | 4955 (19.6%) | |
| 35+ | 879 (8.6%) | 1699 (6.7%) | |
|
| |||
| Birth order c | <1.0E-99 | ||
| First born | 28598 (44.8%) | 13621 (53.9%) | |
| Second born | 19457 (30.5%) | 7583 (30.0%) | |
| Third born | 8432 (13.2%) | 2738 (10.8%) | |
| Fourth or higher born | 7355 (11.5%) | 1336 (5.3%) | |
|
| |||
| Highest educational qualification c | <1.0E-99 | ||
| None | 11375 (17.8%) | 1693 (6.7%) | |
| O-levels, CSEs or equivalent | 16575 (26.0%) | 7496 (29.7%) | |
| A-levels, professional, or equivalent | 14891 (23.3%) | 5708 (22.6%) | |
| Degree | 21001 (32.9%) | 10381 (41.1%) | |
|
| |||
| Refractive error category c | 1.2E-27 | ||
| Non-myopic (>-0.75 D) | 45059 (70.6%) | 16898 (66.8%) | |
| Low/moderate myopia (≤-0.75 D & >-6.00 D) | 16389 (25.7%) | 7231 (28.6%) | |
| High myopia (≤-6.00 D) | 2394 (3.7%) | 1149 (4.5%) | |
a
Values give the mean ± SD.
b
Age completed full time education was only asked of individuals who did not report having a college or University degree.
c
Values give percentage within each sample.