Where they live, how they play: Neighborhood greenness and outdoor physical activity among preschoolers
© Grigsby-Toussaint et al; licensee BioMed Central Ltd. 2011
Received: 29 July 2011
Accepted: 14 December 2011
Published: 14 December 2011
Emerging empirical evidence suggests exposure to "green" environments may encourage higher levels of physical activity among children. Few studies, however, have explored this association exclusively in pre-school aged children in the United States. We examined whether residing in neighborhoods with higher levels of greenness was associated with higher levels of outdoor physical activity among preschoolers. In addition, we also explored whether outdoor playing behaviors (e.g., active vs. quiet) were influenced by levels of neighborhood greenness independent of demographic and parental support factors.
Higher levels of neighborhood greenness as measured by the Normalized Difference Vegetation Index (NDVI) was associated with higher levels of outdoor playing time among preschool-aged children in our sample. Specifically, a one unit increase in neighborhood greenness increased a child's outdoor playing time by approximately 3 minutes. A dose-response relationship was observed between increasing levels of parental support for physical activity (e.g., time spent playing with children) and child outdoor physical activity (p < 0.01).
Consistent with previous studies, neighborhood greenness influences physical activity behavior. However, for preschoolers, parental involvement may be more critical for improving physical activity levels.
Current rates of overweight and obesity among children in the United States (US) are a major public health concern [1–3]. Recent estimates from the National Health and Nutrition Examination Survey (NHANES) show that among 2-to-5 year olds, childhood obesity prevalence ranges from 7% among non-Hispanic White boys, 11% for non-Hispanic White and Mexican American girls, 14% for non-Hispanic Black boys and girls, and 17% for Mexican-American boys . These rates represent an overall doubling of obesity in this age group over the last 30 years . Given the increased risk for myriad health conditions (e.g., impaired glucose sensitivity and cardiovascular disease) that persist into adulthood due to childhood obesity, prevention efforts among pre-school aged children may be warranted [6–8, 3, 9, 10].
The Council on Sports Medicine and Fitness of the American Academy of Pediatrics (AAP) recommends that preschool age children should take part in unstructured free play with an emphasis on running, tumbling, throwing, and catching . However, physical activity (PA) in young children is influenced by the social context including presence of peers, the home environment, and access to green space or parks. A recent review of the literature concludes that there is large inter-individual variability in PA levels with some children being extremely active and others relatively sedentary . Yet to be determined is whether the presence of green space contributes to this inter-individual variability.
Increasing children's exposure to built environments characterized by high levels of "greenness," broadly defined as vegetation such as trees and other plant life, has been shown to reduce obesity risk . Both Bell et al.,  and Liu et al.,  found an inverse relationship between child overweight and residence in neighborhoods with dense vegetation. A suggested rationale for this association is that green neighborhoods are more likely to be both aesthetically pleasing and support more diverse types of physical activity, thus encouraging children to be more active outdoors [13, 16]. This is supported by an evaluation of initiatives using landscape architecture to create green elementary school grounds in Canada, which found a 70% increase in light and moderate physical activity among children . Time spent outdoors has also been shown to increase levels of physical activity among children, particularly among preschoolers [17, 18].
Although emerging empirical evidence suggests an association between neighborhood greenness and reduced risk for overweight, few studies have been conducted exclusively among pre-school aged children. Preschool age children tend to engage in physical activity on a sporadic basis  and rely on their parents or caregivers to create opportunities for structured play and activity  in the US. Thus, future planning for interventions aimed at preschool age children must take the role of the family into account in contrast to school based interventions aimed at older children [19–21]. Furthermore, due to increasing rates of overweight in pre-school aged children and teenagers, it is also critical to develop sustainable preventive strategies to encourage physical activity at an earlier age [4, 22, 3]. Since outdoor play is important for physical activity among pre-school aged children, and neighborhood greenness encourages outdoor physical activity in older children (e.g., school age), we sought to, a) examine whether residing in neighborhoods with higher levels of greenness was associated with higher levels of outdoor physical activity among preschoolers, and, b) to explore whether outdoor playing behaviors (e.g., active vs. quiet) were influenced by levels of neighborhood greenness independent of demographic and parental support factors.
Preschoolers between ages 2-to-5 were recruited as part of the STRONG (S ynergistic T heory and R esearch on O besity and N utrition G roup) Kids Project, a three-wave study over five years which explores childhood obesity within a developmental ecological framework . To ensure socio-economic and racial/ethnic diversity, an unequal probability sampling frame was used to identify licensed day care centers (n = 33) across five counties in Central Illinois. Beginning in January 2009, ninety-one percent (n = 30) of the centers permitted recruitment of children and their parents. A comprehensive self-report questionnaire designed to collect data on demographic characteristics, dietary and physical activity behaviors, and various aspects of parent-child relationships that moderate behaviors related to obesity risk among children was completed by enrolled parents . Response rates among parents ranged from 60% to 95% across centers. Written informed consent was obtained from the parents of the children involved in this study. The data collection procedures for this study were approved by the Institutional Review Board at the University of Illinois at Urbana-Champaign.
Of the 424 surveys collected for wave one at the time of our analysis, 365 were included in our final sample. Fifty-nine cases were excluded due to incomplete addresses or missing data related to gender, race/ethnicity or education. Home addresses provided by parents were geocoded using a web-based geocoding batch program (http://www.gpsvisualizer.com/geocode) supplemented by manual matching. The use of the geocoding batch program allowed us to utilize the most recent commercial geographical database with a high level of accuracy .
To investigate the impact of neighborhood greenness on physical activity levels, satellite images of Landsat Thematic Mapper (TM) from the U.S Geological Survey (USGS) were used to calculate the normalized difference vegetation index (NDVI). The NDVI is the most widely used vegetation index and has been used in numerous studies to estimate vegetation biomass, greenness, and dominant species . The NDVI calculation is based on the ratio between measured reflectivity in the red, and near infrared band, in satellite images because the chlorophyll pigment strongly absorbs radiation in the red band and is highly reflective in the near-infrared band . Consequently, areas with dense vegetation show high values in the infrared band but low values in the red band. According to the NDVI formula, values vary from -1 to +1 . The values close to 1 represent strong vegetation cover, while low values indicate rock and bare soil [15, 25, 26].
Parental self-reported data from the STRONG Kids survey were used to control for the influence of socio-demographic characteristics on our outcomes of interest. Specifically, race/ethnicity, White, compared to all other groups combined (non-White), and gender, were included as binary variables in our models. Non-Whites and females were used as our reference categories Due to the limited sample size of each specific racial/ethnic minority group (e.g., African-American, Asian), to ensure power in our analyses, we collapsed all racial/ethnic minority groups and compared them to Whites. Parental education was categorized as less than a college degree (reference category), college degree, or post-graduate degree. In addition, parental support for physical activity was measured using the following questions from the SPARK survey , "During the past week, how often has an adult in your family done a physical activity or played sports with your child?," and "During the past week, how often has an adult in your family transported your child to a place where he or she can do physical activities or play sports?" The responses were "none", "once," "a few times," and "often." Levels of support were then categorized as low (none), medium (once or a few times), and high (often).
Stata version 11  was used to conduct descriptive and multivariate regression analysis. To explore the influence of neighborhood greenness on total outdoor playing time, a linear regression model was run controlling for race/ethnicity, parental education, and parental support for physical activity. Multinomial regression was used to examine the association between neighborhood greenness and physical activity patterns among children, also controlling for race/ethnicity, parental education, and parental support for physical activity. Children categorized as "rainy day kids" were used as the reference for this analysis. Descriptive statistics were also summarized for all study variables.
On average, the children in our sample engaged in 60 minutes of outdoor playing time per day. Based on guidelines from the National Association for Sport and Physical Activity (NASPE), most children in the sample are meeting the suggested 60 minutes of physical activity each day .
Characteristics of the study population by outdoor playing time (n = 365)
Outdoor playing time a
P -value b
less than college degree
college degree or higher
Parental time spent
playing with child
Parental time spent
transporting child to PA
Characteristics of the study population by physical activity behaviors (n = 365)
Rainy day kids
Outdoor playing time (minutes per day)
Active outdoor playing
Quiet outdoor playing
less than college degree
college degree and over
Parents' intervention: playing with kid
Parents' intervention: transporting child to PA b
Linear regression of neighborhood greenness on outdoor physical activity
B (95% CI)
2.82 (0.21, 5.43)
Gender (ref: female)
4.55 (-1.30, 10.40)
Race/ethnicity (ref: non-white)
6.68 (0.78, 12.50)
(ref: less than college degree)
College degree and more
-4.64 (-10.76, 1.46)
Parental weight status b
-0.42 (-0.87, 0.03)
Time spent playing with child (ref: low)
4.62 (-3.46, 12.72)
9.54 (0.98, 18.10)
Transporting child to PA a (ref: low)
10.64 (4.01, 17.26)
16.48 (8.52, 24.44)
Multinomial logistic regression of neighborhood greenness and physical activity behaviors of children (N = 365)a, b
OR d (95% CI)
OR d (95% CI)
1.32 (1.02, 1.71)
1.02 (0.79, 1.32)
Gender (ref: female)
1.27 (0.71, 2.26)
1.72 (0.96, 3.09)
Race/ethnicity (ref: non-white)
1.87 (1.04, 3.38)
1.42 (0.80, 2.53)
0.98 (0.93, 1.02)
0.97 (0.93, 1.01)
Time spent playing with kid (ref: low)
1.01 (0.44, 2.32)
1.05 (0.47, 2.39)
2.13 (0.89, 5.09)
2.36 (1.00, 5.58)
transporting child to PA c (ref: low)
2.80 (1.45, 5.40)
1.30 (0.67, 2.52)
3.06 (1.41, 6.67)
1.02 (0.45, 2.33)
Our study sought to build upon studies examining aspects of the natural environment that influence childhood obesity risk [13–16]. Consistent with previous studies [14–16], we found that exposure to higher levels of neighborhood greenness may reduce the risk for childhood obesity due to increased physical activity. Specifically, after controlling for socio-demographic and parental support factors, children residing in neighborhoods with higher levels of neighborhood greenness were more likely to engage in outdoor physical activity. To further explore this relationship, we examined whether physical activity behavior (i.e., total outdoor playing time, active vs. quiet play) was influenced by neighborhood greenness. Children living in neighborhoods with the highest levels of neighborhood greenness were more likely to engage in outdoor physical activity (multi-players), and engaged in similar bouts of active and quiet outdoor play. This suggests that exposure to greener neighborhoods encourages children to spend more time outdoors where they may reap both physiological and cognitive benefits [13, 34]. Conversely, children with the lowest levels of neighborhood greenness were least likely to spend time playing outdoors, engaging in active or quiet play (rainy day kids). While neighborhood greenness influenced levels of physical activity among these preschool-aged children, as Cleland et al  observed, parental support factors such as engaging in physical activity with children also plays a role. This may explain why sporty kids were more likely to engage in much more active outdoor physical activity compared to rainy day kids, although both groups lived in areas with similar levels of neighborhood greenness (Table 2). Moreover, although sandbox lovers had higher levels of neighborhood greenness than sporty kids, their parents were least likely to transport them to opportunities for physical activity (Table 2). It is important to note, however, that perhaps the personality of some of the children, such as the rainy day kids, with the tendency to engage in limited outdoor activity, may also influence parents to spend less time transporting them to opportunities for physical activity.
Since the research literature suggests that boys are typically more active than girls between pre-school age and adolescence, we were not surprised to find that boys tended to engage in more physical activity, compared to girls in our sample (Tables 1 and 2) [31, 36, 37]. Socialization by gender, where boys may be encouraged to engage in more physical activity may explain this difference.
While our findings support previous studies exploring the influence of neighborhood greenness on childhood obesity risk, there are some limitations. Our study was cross-sectional, and focused only on levels of physical activity, rather than BMI. Moreover, our measure of physical activity relied on parental reports, rather than objectively measured data collected from accelerometers. Notwithstanding, the quantification of physical activity among preschoolers using accelerometers has been wrought with challenges due to the inability to account for differences in motor and cognitive development that may influence movement patterns [38–40]. While accelerometers seem to be far more effective measuring physical activity among school-age children, standardized methods are still being developed for preschoolers .
Our sample size may have also been too small to give us more robust estimates, as indicated by the wide confidence intervals for some of the results of our regression analyses. Our omission of certain measures of the neighborhood environment may have also influenced our estimates, such as neighborhood walkability, which has been shown to influence overweight among pre-school aged children . We also did not control for neighborhood measures of socioeconomic status, which have been shown to influence childhood overweight, independent of neighborhood greenness . When we included measures of neighborhood SES, however, they were highly correlated with NDVI, so we did not include them in our models to avoid multi-collinearity. Interestingly, when we ran our models using only measures of neighborhood SES to determine whether the NDVI was strictly serving as a proxy for SES, we did not find the same relationship with levels of physical activity. Specifically, while higher levels of neighborhood greenness were associated with higher levels of physical activity, the same did not hold true for higher levels of neighborhood SES. This observation may be due to the fact that the study area encompasses micro-urban and semi-rural areas, where neighborhood SES may be less important for access to greenspace, compared to many urban environments in the US. We also did not account for seasonality based on the time of the year that parents completed the survey. A study by Finn et al. , however, found that seasonality did not influence the total physical activity time of pre-school aged children. In addition, our own analysis (not shown) did not indicate that seasonality influenced levels of physical activity reported by parents.
Another limitation is the use of the area around the home address as the spatial unit for measuring neighborhood greenness. However, we believe that using the home address of pre-school aged children in this sample was the best spatial proxy for measuring the influence of neighborhood greenness on physical activity for several reasons. First, there is some evidence  to suggest that children usually play close to where they live. As such, we attempted to account for areas close to where children live that would encompass nearby playspaces in addition to their backyard, for example. Of course, it is still possible that parents could take their children to places outside of their immediate neighborhoods to engage in active play. Given what the authors know of the study area, however, many families of young children do in fact regularly utilize their neighborhood playspaces. Second, approximately 20% of children in our sample did not attend day care every day, and only 30% of parents reported having their children in day care 40 hours a week. As such, we could only assume that the children were also spending quite a bit of time at their home address. Third, parents were asked to separately report on weekend and weekday physical activity, thus the home address is the only spatial unit that is consistent across all 7 days of the week. Given what we knew of day care attendance in our sample, and park/playspace utilization in the study area, we believe that we used the best spatial proxy for measuring neighborhood greenness based on our study design and resources. We do concede, however, that the use of GPS to actually track the children during the day, or using an activity space log would have more accurately captured the play spaces of the children in our sample.
Another issue that we also explored was the potential cluster effect of day care centers. However, our preliminary analyses showed an intraclass correlation of less than .01. As such we felt confident that the relationships observed in our study were not overestimated.
Despite these limitations, our study also has several strengths. We used an objective measure of neighborhood greenness, and examined both total outdoor playing time and physical activity patterns among children. Our study is also one of the first to examine the influence of the natural environment on childhood obesity risk that focuses exclusively on pre-school aged children and accounts for physical activity behaviors, socio-demographic and parental support factors. By focusing exclusively on pre-school aged children, this allows us to tailor efforts on a critical developmental stage for targeting interventions.
Access to greenspace has been associated with several aspects of human health, including improved mental health and higher levels of physical activity among children and adults [13, 16, 43]. Although largely indirect, evidence from several studies suggests that individuals residing in neighborhoods with access to greenspace are more likely to be imbued with an increased sense of community . Consequently, parents of children residing in these neighborhoods may not only encourage their children to engage in more physical activity, but also ensure that neighborhoods are adequately policed and maintained to facilitate active play. This may explain our results, where higher levels of neighborhood greenness were associated with increased levels of outdoor physical activity among preschoolers. However, parental co-participation in physical activity or transportation to opportunities to engage in physical activity modified the relationship. Our findings further support initiatives to encourage exposure to accessible outdoor green spaces for preschool aged children and their families.
This paper was written on behalf of the STRONG Kids Project Writing Group: Kelly Bost, Sharon Donovan, Kris Harrision, Juhee Kim, Janet Liechty, Brent McBride, Margarita Teran-Garcia, and Angela Wiley. We would also especially like to thank Brenda Koester, Gwen Costa Jacobson, and Anne Bostrom for overseeing data collection by our undergraduate and graduate research teams. Support for this study was provided by the Illinois Council for Food and Agriculture Research (CFAR), the Family Resiliency Center at the University of Illinois, the Center for Health Aging and Disability at the University of Illinois, and the Robert Wood Johnson Foundation Healthy Eating and New Connections grant #66952.
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