Table 3.

Results of multivariable modelling of risk factors associated with any LRTI (model A) and RSV LRTI (models B and C) in children to 2 years in the DCHS

		Model A: LRTI vs no LRTI		Model B: RSV LRTI vs no LRTI		Model C: RSV LRTI vs non-RSV LRTI
		Adjusted IRR (95% CI)	p value	Adjusted IRR (95% CI)	p value	Adjusted IRR (95% CI)	p value
Male sex (vs female)		1·48 (1·22–1·79)	<0·0001	1·16 (0·92–1·48)	0·21	0·77 (0·62–0·94)	0·01
Socioeconomic quartile (vs high)
	Lowest	1·24 (0·92–1·65)	0·15	1·05 (0·72–1·54)	0·79	0·86 (0·62–1·18)	0·34
	Low–moderate	1·34 (1·02–1·77)	0·04	1·27 (0·91–1·77)	0·17	0·89 (0·66–1·19)	0·42
	Moderate–high	1·05 (0·79–1·39)	0·75	1·16 (0·81–1·65)	0·42	1·02 (0·76–1·36)	0·89
Presence of other children in the household		0·92 (0·66–1·28)	0·61	1·06 (0·71–1·60)	0·78	1·19 (0·84–1·69)	0·33
HIV exposed (vs HIV unexposed)		1·49 (1·20–1·86)	<0·0004	1·37 (1·04–1·81)	0·027	0·87 (0·69–1·11)	0·28
Maternal smoking after birth (self-reports; vs non-smoker)		1·09 (0·88–1·35)	0·43	1·33 (1·04–1·70)	0·025	1·38 (1·11–1·72)	0·0035
Preterm (<37 weeks' gestation)		1·20 (0·93–1·4)	0·17	1·06 (0·78–1·43)	0·72	0·92 (0·66–1·27)	0·60
Low birthweight (weight <2·5 kgs)		1·48 (1·15–1·91)	0·0023	1·31 (0·98–1·77)	0·070	0·92 (0·66–1·28)	0·62
Season of birth (vs summer)
	Autumn (Mar–May)	1·42 (1·11–1·81)	0·0058	1·48 (1·11–1·97)	0·0071	1·13 (0·88–1·45)	0·35
	Winter (June–Aug)	0·93 (0·71–1·20)	0·57	0·77 (0·53–1·11)	0·16	0·86 (0·63–1·17)	0·35
	Spring (Sept–Nov)	0·97 (0·73–1·28)	0·83	0·58 (0·36–0·93)	0·024	0·65 (0·42–0·99)	0·046
Age at LRTI (or mid interval if no LRTI; years)		0·46 (0·40–0·52)	<0·001	1·00 (1·00–1·00)	<0·0001	0·79 (0·64–0·97)	0·025
Exclusive breastfeeding at 6 weeks		0·96 (0·79–1·17)	0·70	0·98 (0·77–1·25)	0·87	1·00 (0·80–1·24)	0·98

Results of generalised estimating equations expressed as incidence rate ratios (IRRs) and 95% CI. Models include all variables shown. LRTI=lower respiratory tract infection. RSV=respiratory syncytial virus. DCHS=Drakenstein Child Health Study.