Rhinoconjunctivitis among Adolescents in Kuwait and Associated Risk Factors: A Cross-Sectional Study

Table 4

Crude and adjusted associations between the total number of siblings, number of older siblings, and number of younger siblings and current rhinoconjunctivitis.

	Rhinoconjunctivitis, % (n/total)	Crude PR (95% CI)	Adjusted PR^† (95% CI)
Total siblings
0	18.0 (7/39)	1.00 (ref.)	1.00 (ref.)
1	15.8 (32/202)	0.88 (0.42–1.86)	0.84 (0.42–1.69)
2	15.8 (60/381)	0.88 (0.43–1.79)	0.81 (0.41–1.57)
3	16.9 (116/688)	0.94 (0.47–1.88)	0.86 (0.45–1.65)
≥4	11.9 (277/2330)	0.66 (0.34–1.31)	0.62 (0.33–1.18)
Per additional sibling	—	0.91 (0.87–0.95)	0.92 (0.88–0.96)
Ptrend	—	<0.001	<0.001
Older siblings
0	14.4 (152/1055)	1.00 (ref.)	1.00 (ref.)
1	14.3 (112/784)	0.96 (0.77–1.21)	0.93 (0.74–1.16)
2	16.5 (101/614)	1.04 (0.82–1.32)	0.98 (0.77–1.23)
3	11.8 (57/485)	0.74 (0.55–0.99)	0.71 (0.53–0.95)
≥4	10.0 (74/743)	0.61 (0.45–0.81)	0.59 (0.44–0.80)
Per additional older sibling	—	0.90 (0.86–0.95)	0.90 (0.85–0.94)
Ptrend	—	<0.001	<0.001
Younger siblings
0	13.1 (69/526)	1.00 (ref.)	1.00 (ref.)
1	13.9 (102/736)	0.98 (0.73–1.30)	0.97 (0.72–1.30)
2	14.9 (113/761)	0.98 (0.73–1.30)	1.02 (0.76–1.36)
3	14.8 (114/770)	0.92 (0.69–1.23)	0.94 (0.70–1.27)
≥4	11.1 (92/831)	0.68 (0.50–0.92)	0.74 (0.54–1.01)
Per additional younger sibling	—	0.93 (0.88–0.98)	0.94 (0.89–1.00)
Ptrend	—	0.008	0.050

PR: prevalence ratio; CI: confidence interval; ref.: reference. PRs of older siblings were simultaneously adjusted for younger siblings, and PRs of younger siblings were simultaneously adjusted for older siblings. ^†Adjusted for sex, age, body mass index, mode of birth, current cat exposure, dog exposure in infancy, environmental tobacco smoke exposure, parental history of rhinitis, parental history of asthma, and parental history of eczema. Additionally, PRs of older siblings were simultaneously adjusted for younger siblings, and PRs of younger siblings were simultaneously adjusted for older siblings.