Poverty, urban-rural classification and term infant mortality: a population-based multilevel analysis

Yousra A. Mohamoud,Deborah B. Ehrenthal,Russell S. Kirby

doi:10.1186/s12884-019-2190-1

Yousra A. Mohamoud, Deborah B. Ehrenthal + Show 1 more

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https://doi.org/10.1186/s12884-019-2190-1

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Abstract

BackgroundU.S. mortality rate of term infants is higher than most other developed countries. Term infant mortality is associated with exogenous socio-environmental factors. Previous research links low socioeconomic status and rurality with high infant mortality, but does not examine the effect of individual level factors on this association. Separating out the effect of contextual factors from individual level factors has important implications for targeting interventions. Therefore, we aim to estimate the independent effect of poverty and urban-rural classification on term infant mortality.MethodsWe used linked 2013 period cohort birth-infant death files from the National Center for Health Statistics (NCHS). Counties were assigned to low, medium and high poverty groups using US Census Bureau county-level percent of children ≤18 years living in poverty, and were classified based on NCHS urban-rural classification. Bivariate and multilevel logistic regression models were used to estimate odds of term infant death, accounting for individual and county level variables.ResultsThere were 2,551,828 term births in 2013, with an overall term mortality of 2.1 per 1000 births. Odds of term infant mortality increased from 1.4 (95% CI: 1.2, 1.6) to 1.8 (95% CI: 1.6, 2.0) comparing births over increasing county poverty to those in the lowest. The associations remained significant in the multivariable model, for highest poverty 1.3 (95% CI: 1.1, 1.5). Similarly, the odds of term infant mortality increased with increasing rurality, from 1.3 (95% CI: 1.2, 1.5) in medium metro counties to 1.7 (95% CI: 1.5, 2.0) in non-core counties compared to large fringe metro counties. However, only rural non-core counties remained statistically associated with increased risk of term infant mortality after adjusting for individual level maternal characteristics.ConclusionsHigh poverty and very rural counties remained associated with term infant mortality independent of individual maternal sociodemographic, health and obstetric factors. Interventions should focus on contextual factors such as economic environment and availability of health and social services in addition to individual factors to reduce term infant mortality.

Highlights

U.S mortality rate of term infants is higher than most other developed countries
2010 model-based small county poverty estimates produced by the U.S Census Bureau [13] and the 2013 National Center of Health Statistics (NCHS) Urban-Rural Classification scheme for counties which is based on the Office of Management and Budget’s (OMB) February 2013 delineation of metropolitan statistical areas (MSA) and micropolitan statistical areas and Vintage 2012 post-censal estimates of the resident U.S population [14]
Multilevel logistic regression modelling was conducted to determine the association between poverty, urban-rural classification and term infant mortality, and whether this association was mediated by individual level sociodemographic, maternal health and obstetric characteristics

Summary

Introduction

U.S mortality rate of term infants is higher than most other developed countries. Term infant mortality is associated with exogenous socio-environmental factors. One study identified term births as “a period of heterogeneous risk”, found that term deaths tend to occur in the postneonatal period, with accidents, assault and sudden infant death syndrome (SIDS) being the leading causes [2] Deaths during this period are more likely to be associated with exogenous socio-environmental factors such as housing conditions, infant sleep environment, access to health care, nutrition and social services [3]. Fewer studies have looked at contextual socioeconomic disadvantage and infant mortality Those that do, tend to adjust for only a minimal set of individual level factors [9, 10]. While studies show higher IMR, postneonatal mortality, in rural counties compared to urban counties, none adjust for individual level factors to isolate contextual rural-urban class effects [11, 12]

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