Infant mortality in South Africa - distribution, associations and policy implications, 2007: an ecological spatial analysis

Table 1 Univariate and Bayesian multivariable infant mortality risk factor analysis, South Africa, 2007

Indicator	Univariate analysis		Multivariable analysis
	Zero-inflated Poisson model		Zero-inflated convolution CAR ⁱ spatial Poisson model
	IRR (95% CI)	p-value	IRR (95% BCI ⁱⁱ)	p-value
Proportion of previous siblings that have died	1.135 (1.13,1.141)	<0.001	1.032 (0.989,1.081)	0.088
Proportion of mothers that have died	1.108 (1.104,1.113)	<0.001	1.034 (1,1.073)	0.025
HIV antenatal sero-prevalence ⁱⁱⁱ in 2007	1.035 (1.034,1.037)	<0.001	1.017 (1,1.037)	0.022
Ratio of male to female infants	1.042 (1.041,1.043)	<0.001	1.021 (1.013,1.029)	<0.001
Gini-coefficient for income inequality	1.017 (1.016,1.019)	<0.001	1.003 (0.994,1.014)	0.266
Proportion of females with no schooling	1.031 (1.03,1.032)	<0.001	^v	---
Poor basic service delivery ^iv	1.009 (1.009,1.009)	<0.001	^v	---
Combined lack of female schooling and basic service delivery indicators	1.012 (1.011,1.012)	<0.001	1.003 (0.993,1.002)	0.912
Constant (b0)	---	---	-1.198 (-1.664,-0.727)	---
σ²_ε (unstructured sub-district heterogeneity)	---	---	0.446 (0.352,0.552)	---
σ²_φ (spatially structured heterogeneity)	---	---	0.015 (0,0.142)	---

i: Incorporated an unstructured sub-district random effect and a structured normal CAR spatial random effect;ii: Bayesian credibility interval; iii: District level; iv: includes lack of basic service (water, toilet and rubbish disposal) and increasing ratio of infants to clinics within the sub-district
v: in multivariable model we have combined lack of female schooling with poor basic service delivery as they are strongly correlated (ρ = 0.5633, p < 0.01)