Assessing the impact of the local environment on birth outcomes: a case for HLM

Abstract

Hierarchical linear Models (HLM) is a useful way to analyze the relationships between community level environmental data, individual risk factors, and birth outcomes. With HLM we can determine the effects of potentially remediable environmental conditions (e.g., air pollution) after controlling for individual characteristics such as health factors and socioeconomic factors. Methodological limitations of ecological studies of birth outcomes and a detailed analysis of the varying models that predict birth weight will be discussed. Ambient concentrations of criterion air pollutants (e.g., lead and sulfur dioxide) demonstrated a sizeable negative effect on birth weight; while the economic characteristics of the mother's residential census tract (ex. poverty level) also negatively influenced birth weight.

Spatial variations in the associations of birth weight with socioeconomic, environmental, and behavioral factors in Georgia, USA

“…It had a significant negative relationship with birth weight in most parts of the state. These results are consistent with the findings from numerous previous studies (Adriaanse et al, 1996;Bailey & Byrom, 2007;Bell et al, 2007;Reichman & Teitler, 2005;Williams et al, 2007;Young et al, 2010). Compared to the cases with non-significant relationships, the births with significant relationships tended to be located in rural communities with lower family incomes and lower educational attainment.…”

“…Significant positive associations of birth weight with both family median income and educational attainment were found in approximately half of the state. These results agree with the findings from some previous studies, which found that lower birth weight was associated with mothers living in communities with lower SES (Buka et al, 2003;Morello-Frosch et al, 2010;Williams et al, 2007). However, non-significant relationships were also observed in the rest of the state, which means that neighborhood context may not be as important in affecting birth weight after controlling for three key individual-level behavioral variables in these areas.…”

“…These results indicate that the births located in communities with higher family income and educational attainment tend to have higher birth weight. These findings are consistent with the findings from some previous studies (Morello-Frosch et al, 2010;Williams et al, 2007). Maternal drinking and smoking, adequacy of prenatal care, and percentage of urban land have negative relationships with birth weight.…”

“…Therefore, census tract-level income (family median income), educational attainment (rate of residents with high school and above education), and land use (percentage of urban land) were used to examine the associations of birth weight with communitylevel socioeconomic and environmental factors. Census tracts were chosen to represent communities because census tract is the most commonly used spatial unit to analyze the relationship between birth weight and neighborhood characteristics (Nkansah-Amankra, 2010; Williams et al, 2007). Using census tracts instead of other units (e.g.…”

“…However, the findings on the effects of the community-level variables from different studies are also inconsistent as reported in the literature. For instance, an investigation of the relationships between birth outcomes and community-level demographic, socioeconomic, and environmental characteristics among 14,194 births in Tennessee suggested that community-level poverty had a significant association with birth weight (Williams, Rennock-Román, Suen, Magsumbol, & Ozdenerol, 2007). Morello-Frosch, Jesdale, Sadd, and Pastor (2010) reported that a higher risk of LBW was associated with a lower census tract-level educational attainment rate in California.…”