Greenness around schools associated with lower risk of hypertension among children: Findings from the Seven Northeastern Cities Study in China
Greater greenness near schools is associated with lower blood pressure, especially in overweight or obese children in China
Research on the protective role of nearby greenness on high blood pressure has focused primarily on residential greenness. This study investigated the association between greenness around schools and blood pressure among children in China.
The study included 9354 children (age 4-17) from 62 schools in seven cities in Northeast China. Two satellite-derived measures of greenness were used: NDVI (Normalized Difference Vegetation Index) and SAVI (Soil-Adjusted Vegetation Index). Because blood pressure is reported to be associated with ambient air pollution and nearby greenness, two measures of air pollution were also used: one based on estimates of particulate matter concentrations; the other on nitrogen dioxide concentrations. Participating children completed a physical examination; and parents or guardians of the participating children completed a survey focusing on demographic information and environmental exposure. Blood pressure measures of all the participating children were completed according to the guidelines of the American Academy of Pediatrics.
The data showed that higher greenness was consistently associated with lower blood pressure. Children attending schools with higher greenness were thus at lower risk of hypertension. While hypertension is less common in children than in adults, it often originates in childhood and may track into adolescence and adulthood. The beneficial effects of higher greenness were stronger in children with higher BMI (body mass index) levels. These results remained consistent even when family income and parent education level were considered. The data also showed that higher levels of greenness were significantly associated with lower levels of air pollution. Further analysis indicated that air pollution might partially mediate the effects of greenness on blood pressure.
This research suggests that policy makers would do well to incorporate more green space in the environments where children live, play, and go to school. Such initiatives could have short- and long-term health benefits for children, especially for children living in urban environments where less greenery and more air pollution are recognized as health-related concerns.