Cross-level interaction between individual education and regional chemical fertilizer consumption on the risk of hypertension: evidence from the China hypertension survey

Hypertension is a common and costly public health burden in China, while the interaction effects of individual and contextual level factors on the risk of hypertension remain unclear. This study aimed to investigate whether the interaction effects between individual education and regional chemical fertilizer consumption are associated with the risk of hypertension based on a cross-level interaction perspective. Data was from the China Hypertension Survey (CHS) study, which used a nationally representative sample, and was conducted between 2012 and 2015. A total of 379 467 participants aged over 18 years from 221 counties in 31 provinces were included. A cross-sectional study design and two-level logistic models were conducted to investigate the cross-level interaction between individual education and regional chemical fertilizer consumption on the risk of hypertension after adjusting for potential confounding variables. Compared to individuals with high education (college or more), the adjusted OR (95%CI) for hypertension among those in the high school, middle school, and elementary school or less was 1.16 (1.12-1.21), 1.25 (1.20-1.30), and 1.49 (1.43-1.55), respectively. The association between regional chemical fertilizer consumption and hypertension was not significant. Interaction analysis showed that regional chemical fertilizer consumption was associated with an increased risk of hypertension for individuals with lower education. These patterns were consistent after stratified by sex. This study provided evidence from the Chinese population that interaction between individual education and regional chemical fertilizer was associated with risk of hypertension. Future research and policy aimed to improve population health and reduce hypertension could address the regional context of population as well as individual factors.

Spatial variation and association between maternal chemical fertilizer exposure and preterm birth in a rural area in Northern China

Whether maternal macro-environmental chemical fertilizer exposure has an association with the risk of preterm birth remains unclear. This study aimed to investigate the association between maternal exposure to chemical fertilizer during pregnancy and the risk of preterm birth. A total of 13,861 births, including 402 preterm birth from 313 villages in Pingding County, Shanxi Province, China, were analyzed to explore spatial variations of preterm birth risks at the village level. Spatial variations of preterm birth were visualized and tested with Disease Mapping, Moran's I and G* Statistic. The spatial zero-inflated negative binomial model was used to evaluate the incidence rate ratio (IRR) of preterm birth in different chemical fertilizer consumption levels at the village level. A population-based case-control study was conducted including 153 preterm births cases and 204 controls at the household level. The two-level logistic regression model was performed to estimate the association between risks of preterm birth and maternal exposure to chemical fertilizer after adjusting confounding factors. The findings indicated a remarkably clustering effect in relative risks of preterm birth and identified a high-risk clustering region of preterm birth from the south-central to the southwest and a low-risk clustering region in the northern Pingding county. The results of the spatial zero-inflated negative binomial model showed that the risk of preterm birth in the villages with chemical fertilizer consumption≥100 tons was 2.82 (95% CI: 1.50-5.57) times higher than those with <50 tons. Maternal exposure to chemical fertilizer ≥100 tons at village level was associated with an increased risk of preterm birth (aOR 2.14, 95%CI: 1.18-3.96), compared with exposure <50 tons after adjusting for confounding variables. The findings suggests that chemical fertilizers deserve more attention as a potential risk factor of preterm birth.