Greenspace, physical activity, and BMI in children from two cities in northern Mexico

Abstract

Numerous previous studies have reported positive associations between exposure to greenspace and children's physical activity, but in high-income countries only. Prior studies have also examined greenspace and obesity in children, but these have yielded inconsistent results and focused mostly on older children. The purpose of this study was to assess associations between time children spent in greenspace as the primary exposure and our outcomes of interest, including 1) minutes of physical activity, and 2) body mass index (BMI) z-score. Our sample was 102 children ages 3 to 5 years living in Ensenada and Tijuana, Mexico. We fit linear mixed models to estimate associations between greenspace and children's physical activity and BMI z-score. After adjustment for potential confounders, greater time in greenspace was associated with decreased sedentary time (-0.08 min per hour for each additional 30 min in greenspace; 95% CI -0.13, -0.04; p = 0.002) and increased moderate-to-vigorous physical activity (MVPA) (0.06; 95% CI 0.03, 0.10; p < 0.001). Results were driven primarily by children in Tijuana (-0.22; 95% CI -0.38, -0.06; p = 0.008 for sedentary time and 0.15; 95% CI 0.06, 0.38; p = 0.007 for MVPA). Time in greenspace was not associated with BMI z-score in children in Ensenada (0.001; 95% CI -0.008, 0.01; p = 0.83) or Tijuana (-0.009; 95% CI -0.02, 0.004; p = 0.17). Greater time in greenspace was associated with physical activity but not BMI in our sample of children-more so in Tijuana compared to Ensenada. Given high rates of obesity, interventions should aim to increase physical activity in young children in Northern Mexico.

Keywords: BMI, body mass index; GPS, global positioning system; Global positioning system; Greenspace; MVPA, moderate-to-vigorous physical activity; NDVI, Normalized Difference Vegetation Index; Normalized Difference Vegetation Index; Obesity; Physical activity.

Fig. 1

Normalized Difference Vegetation Index (NDVI) values to conceptualize greenspace (green vegetation density) in Tijuana (a) and Ensenada (b).