Table 3.

OR for getting rheumatoid arthritis among the infant-exposed group comparing with two reference groups, stratified by region, sex and BMI

Stratified factors	Infant-exposed group (reference: non-exposed group)	Infant-exposed group (reference: age-balanced group†)
	1.44 (1.28 to 1.63)***	1.17 (1.03 to 1.336)*
Region
Rural	1.31 (1.05 to 1.63)*	1.12 (0.92 to 1.37)
Non-severe	1.20 (0.90 to 1.60)	1.10 (0.84 to 1.42)
Severe	1.40 (0.90 to 2.16)	0.99 (0.67 to 1.44)
P value for difference	<0.05	<0.05
Urban	1.57 (1.28 to 1.93)***	1.22 (1.02 to 1.46)*
Non-severe	1.46 (1.09 to 1.94)**	1.19 (0.92 to 1.52)
Severe	1.80 (1.24 to 2.60)**	1.27 (0.92 to 1.74)
P value for difference	<0.001	<0.001
Sex
Male	1.24 (0.98 to 1.57)	1.24 (0.95 to 1.59)
Female	1.44 (1.20 to 1.72)***	1.15 (1.02 to 1.34)*
P value for difference	<0.001	<0.001
BMI
BMI <24	1.40 (1.13 to 1.73)**	1.07 (0.88 to 1.30)
BMI ≥24	1.49 (1.20 to 1.83)***	1.28 (1.06 to 1.53)**
P value for difference	<0.001	<0.001

All analyses were adjusted for monthly income, highest education, alcohol consumption, tobacco use, BMI and metabolic equivalent of task hours.

*P<0.05, **P<0.01, ***P<0.001.

†Combined prenatal-exposed and preschool-exposed groups.

BMI, body mass index.