Greenspace, Air Pollution, Neighborhood Factors, and Preeclampsia in a Population-Based Case-Control Study in California.

To investigate preeclampsia etiologies, we examined relationships between greenspace, air pollution, and neighborhood factors. Data were from hospital records and geocoded residences of 77,406 women in San Joaquin Valley, California from 2000 to 2006. Preeclampsia was divided into mild, severe, or superimposed onto pre-existing hypertension. Greenspace within 100 and 500 m residential buffers was estimated from satellite data using normalized difference vegetation index (NDVI). Air quality data were averaged over pregnancy from daily 24-h averages of nitrogen dioxide, particulate matter <10 µm (PM10) and <2.5 µm (PM2.5), and carbon monoxide. Neighborhood socioeconomic (SES) factors included living below the federal poverty level and median annual income using 2000 US Census data. Odds of preeclampsia were estimated using logistic regression. Effect modification was assessed using Wald tests. More greenspace (500 m) was inversely associated with superimposed preeclampsia (OR = 0.57). High PM2.5 and low SES were associated with mild and severe preeclampsia. We observed differences in associations between greenspace (500 m) and superimposed preeclampsia by neighborhood income and between greenspace (500 m) and severe preeclampsia by PM10, overall and among those living in higher SES neighborhoods. Less greenspace, high particulate matter, and high-poverty/low-income neighborhoods were associated with preeclampsia, and effect modification was observed between these exposures. Further research into exposure combinations and preeclampsia is warranted.

Residential proximity to green space and preeclampsia in California.

BACKGROUND: We investigated whether residing near more green space might reduce the risk of preeclampsia. METHODS: Participants were women who delivered a live, singleton birth between 1998 and 2011 in eight counties of the San Joaquin Valley in California. There were 7276 cases of preeclampsia divided into mild, severe, or superimposed on preexisting hypertension. Controls were 197,345 women who did not have a hypertensive disorder and delivered between 37 and 41 weeks. Green space was estimated from satellite data using Normalized Difference Vegetation Index (NDVI), an index calculated from surface reflectance at the visible and near-infrared wavelengths. Values closer to 1 denote a higher density of green vegetation. Average NDVI was calculated within a 50 m, 100 m, and 500 m buffer around each woman's residence. Odds ratios and 95% confidence intervals were estimated comparing the lowest and highest quartiles of mean NDVI to the interquartile range comparing each preeclampsia phenotype, divided into early (20-31 weeks) and late (32-36 weeks) preterm birth, to full-term controls. RESULTS: We observed an inverse association in the 500 m buffer for women in the top quartile of NDVI and a positive association for women in the lowest quartile of NDVI for women with superimposed preeclampsia. There were no associations in the 50 and 100 m buffers. CONCLUSION: Within a 500 m buffer, more green space was inversely associated with superimposed preeclampsia. Future work should explore the mechanism by which green space may protect against preeclampsia.