Satellite-Based and Street-View Green Space and Adiposity in US Children
This study found a significant association between higher levels of green space (especially "other green space" like flowers and fields) and lower adiposity, particularly in late adolescence, with some variations by sex. The findings suggest that increasing residential green space could be a valuable strategy for mitigating childhood obesity.
College of Health researcher(s)
Highlights
Key Points
Question
Is residential green space exposure, assessed using the satellite-based normalized difference vegetation index (NDVI) and street-view imagery, associated with adiposity measures from childhood to adolescence?
Findings
In this US-based cohort study of 843 children, a higher satellite-based NDVI in early adolescence was associated with lower body mass index (BMI), waist circumference, and total body and trunk fat mass in late adolescence. More street-view other green space components (flowers, plants, and fields) were also associated with a lower BMI in the same period.
Meaning
This study suggests that increasing the overall residential green space and specific green space components could potentially mitigate the prevalence of childhood obesity.
Abstract
Importance
Green space may be associated with obesity outcomes in children by promoting physical activity and reducing stress. However, previous studies have mostly used a single measure of green space and body mass index (BMI) as the sole indicator of adiposity.
Objective
To examine associations of the satellite-based normalized difference vegetation index (NDVI) and street-view imagery–based green space metrics with comprehensive adiposity measures in children.
Design, setting, and participants
The Project Viva cohort study observed participants from mid-childhood (mean [SD] age, 8.0 [0.8] years) and early adolescence (mean [SD] age, 13.3 [1.0] years) through late adolescence (mean [SD] age, 17.8 [0.7] years) between January 1, 2007, and December 31, 2021. This analysis included children with data on green space and adiposity measures. Data were analyzed from January 1 to June 30, 2024.
Exposures
Green space metrics (ie, percentage of trees, grass, and other green space) using street-view imagery and deep learning algorithms along with the NDVI were linked with participants’ home addresses during mid-childhood and early adolescence.
Main outcomes and measures
Body mass index (calculated as weight in kilograms divided by height in meters squared) and waist circumference z scores were calculated from anthropometric measurements during early and late adolescence. The total fat mass index (FMI; calculated as fat mass in kilograms divided by height in meters squared) and trunk FMI were obtained using dual-energy x-ray absorptiometry. Separate linear regression models adjusted for a child’s age, sex, individual and neighborhood socioeconomic status, and population density estimated prospective associations of the NDVI and street-view green space (in mid-childhood or early adolescence) with 4 adiposity measures (in early or late adolescence).
Results
The sample included 843 children (mean [SD] age at mid-childhood, 7.9 [0.8] years; 423 girls [50.2%]) at baseline. After adjustment for confounders, a higher NDVI (per 1-SD increase) within 270 m in early adolescence was associated with lower z scores for BMI (−0.16 [95% CI, −0.27 to −0.04]) and waist circumference (−0.13 [95% CI, −0.23 to −0.03]), as well as a lower total FMI (−0.62 [95% CI, −1.02 to −0.23]) and trunk FMI (−0.33 [95% CI, −0.55 to −0.12]) in late adolescence. Higher percentages of street-view other green space (flowers, plants, and fields), but not street-view trees and grass, within 500 m in early adolescence were associated with lower BMI z scores (−0.09 [95% CI, −0.18 to −0.01) in late adolescence. The NDVI and street-view green space exposure at mid-childhood were not associated with adiposity measures in early adolescence.
Conclusions and relevance
This cohort study of US children suggests that higher levels of satellite-based NDVI greenness and percentages of street-level green space components (flowers, plants, and fields) were associated with lower adiposity. The findings support the exploration of increasing residential green space levels and adding specific green space components as an urban planning and public health intervention strategy to combat the prevalence of childhood obesity in the US.
FAQ on Green Space and Childhood Adiposity
What is the main goal of this study and why is it important?
This study aims to investigate the relationship between green space exposure and adiposity (body fat) in children from mid-childhood through late adolescence. Previous studies have primarily used a single measure of greenness (like NDVI) and BMI, limiting understanding. This research uses both satellite-based greenness measures (NDVI) and street-level imagery to measure specific types of green space (trees, grass, other green spaces like flowers, plants, fields) and their association with multiple adiposity measures, including waist circumference, total fat mass, and trunk fat mass. This is crucial because childhood obesity has serious physical and psychosocial consequences, and understanding modifiable environmental factors is key for prevention.
How was green space measured in the study?
The study used two primary methods: satellite-based Normalized Difference Vegetation Index (NDVI) and street-view imagery analysis. The NDVI measures the overall greenness level in an area, while street-view imagery, using deep-learning algorithms, identifies and quantifies the percentage of trees, grass, and other green space components within different buffer distances (100m, 500m, and 1000m) from a child's home. This approach provides a comprehensive view by capturing both overall greenness and specific types of visible vegetation at street level.
What were the main findings regarding the relationship between green space and childhood adiposity?
The study found that higher levels of satellite-based NDVI greenness in early adolescence were associated with lower BMI, waist circumference, total fat mass, and trunk fat mass in late adolescence. Additionally, a higher percentage of "other green space" (flowers, plants, and fields) visible in street-view images during early adolescence was also associated with a lower BMI in late adolescence. Interestingly, while the study initially hypothesized street-level green space metrics would be more strongly associated with adiposity, the satellite-based NDVI showed a stronger association with multiple adiposity measures in this study. Green space exposure at mid-childhood was not associated with adiposity in early adolescence.
Why was early adolescence identified as a key period for these associations?
The study found that green space exposure in early adolescence had a more significant impact on later adiposity than green space exposure in mid-childhood. This could be due to various reasons, including the fact that during early adolescence, children gain more autonomy to use their local environment for recreation and social activities. Thus, the presence and types of green spaces in their neighborhoods may directly affect their physical activity, stress levels, and sleep patterns, which in turn impact adiposity. The benefits associated with green space may accumulate over time and the influence of parental controls over activity diminishes as they enter adolescence, leading to a stronger impact.
Did the study find any differences in these associations based on the child's sex?
Yes, the study found significant differences based on sex. Girls showed a stronger association between street-view trees and lower adiposity, as well as a stronger association between NDVI and lower BMI and waist circumference. However, boys had a stronger association between street-view "other green space" and lower BMI. This could indicate that girls might benefit more from the overall presence of trees, while boys might be more sensitive to the aesthetics and utility of specific "other green space" features for activities, which may help combat obesity.
What are the implications of these findings for urban planning and public health?
The findings suggest that increasing residential green space and adding specific green space components (like flowers, plants, and fields) could be a promising urban planning and public health strategy to combat childhood obesity. Given that early adolescence was found to be a key period, interventions focused on improving the access and quality of green space in neighborhoods where adolescents live may yield significant results. The potential to integrate nature into urban design offers a long-term approach to obesity prevention that can work alongside more individualized intervention strategies.
What are the strengths and limitations of this study?
Strengths: This study used objective measures of adiposity, including total and trunk fat mass from DXA scans, and comprehensive green space measures using both satellite NDVI and street-view imagery, enabling nuanced analysis. The study's longitudinal design provided insights into the temporal relationship between green space exposure and changes in adiposity and is the first to examine street-level green space, as well as satellite-based greenness on childhood obesity in a longitudinal study. Limitations: Street-view images are just snapshots and might not capture the true green space over time. The study did not assess green space exposure before mid-childhood, nor did it account for the participants' perceived quality of green space or how they actually used it. Also, the study population was mostly non-Hispanic White participants from higher socio-economic backgrounds in Massachusetts, potentially limiting the generalizability of findings to more diverse groups in different locations.
How does this research contribute to what we already know about green space and obesity?
This research provides more comprehensive evidence supporting the relationship between green space and lower adiposity in children, especially during early adolescence. By using both satellite-based and street-view data, and examining specific components of green space, this study adds to our understanding about what aspects of green space might be more influential. Furthermore, the study highlights that interventions in early adolescence are more likely to impact long-term health. The sex-specific analysis also reveals that green space interventions may need to be designed differently for boys and girls to be maximally effective. The study emphasizes the potential of incorporating more nature into urban environments as an approach to combat childhood obesity.