. Author manuscript; available in PMC: 2014 Jun 1.

Published in final edited form as: Ophthalmic Epidemiol. 2013 Oct 29;20(6):10.3109/09286586.2013.848457. doi: 10.3109/09286586.2013.848457

Table 2. Demographic characteristics of the study groups by birth order.

	Number of subjects (%)

Birth order	ALSPAC	SCORM	REHS	IDFC
1	2168 (49.3%)	1800 (91.9%)	597 (47.2%)	NA
2	1525 (34.7%)	155 (7.9%)	382 (30.2%)	NA
3	532 (12.1%)	4 (0.2%)	186 (14.7%)	NA
≥4	176 (4.0%)	-	101 (8.0%)	NA

	Age of subjects (mean ± S.D.) in years

Birth order	ALSPAC	SCORM	REHS	IDFC
1	15.4 ± 0.3	13.1 ± 2.3	20.0 ± 0.4	NA
2	15.4 ± 0.3	12.6 ± 2.2	20.1 ± 0.5	NA
3	15.4 ± 0.3	13.0 ± 0.0	20.1 ± 0.5	NA
≥4	15.4 ± 0.3	-	20.0 ± 0.4	NA

NA: Information not available for release.