Previous research has found longitudinal associations between children’s proximity to green space (e.g., parks) and their body mass index (BMI) [
Weight status is routinely used to assess children’s risk for health complications and cardiovascular disease in later life. While BMI is the most widely used measure, evidence suggests that waist circumference (WC) and waist-to-height ratio (WtHR) may be better predictors of cardiovascular disease in children [
To the authors’ knowledge, no previous study has examined the role of green space on children’s WC or WtHR, with previous research relying on either objectively measured (e.g., [
Data for this study comes from the Longitudinal Study of Australian Children (LSAC). The full methodology of the LSAC is described elsewhere [
Two measures of weight status were the outcome variables for the present study: WC and WtHR. Weight status was measured biennially during face-to-face interviews. The interviewer measured the child’s height and WC to the nearest 0.1 cm using a portable stadiometer (Invicta, Code IPO955) and a tape measure. Two measurements were taken and the average used. When the difference between the measures was >0.5 cm, a third measurement was taken and the average of the two closest measures was used [
The proportion of neighbourhood green space was calculated for each statistical area level 2 (SA2), the smallest area measure available in the LSAC [
As socioeconomic and demographic status are likely confounders in the relationship between green space and weight status [
Multilevel linear regression was used to model the influence of neighbourhood green space on difference measures of weight status, to account for clustering within neighbourhoods. A “null” model was fit first, consisting of only the outcome measure and the following hierarchical structure: the measure of weight status at each time point (level 1), nested within individuals (level 2), and nested within Statistical Areas Level 2s (level 3). Polynomial functions of age were tested for each outcome measure and included only where they significantly improved model fit. Green space was then added (model 1), followed by a green space by age interaction (model 2). Finally, an adjusted model was fit, controlling for socioeconomic status (model 3). Log-likelihood tests were used to determine if explanatory variables significantly impacted on the models, with significance levels set at 5%. Multilevel model growth curves were generated from the final models to further investigate the associations. To investigate gender differences in weight status trajectories, we chose to fit gender-stratified models for all outcomes. All statistical analysis was conducted using STATA 12 (StataCorp, College Station, TX, USA).
The sample is described in Table
Sample characteristics.
Wave 2 | Wave 3 | Wave 4 | Wave 5 | |||||
---|---|---|---|---|---|---|---|---|
Boys | Girls | Boys | Girls | Boys | Girls | Boys | Girls | |
Sample | 2277 | 2187 | 2212 | 2119 | 2133 | 2036 | 2021 | 1935 |
Age in years (SD) | 6.28 (0.45) | 6.30 (0.46) | 8.26 (0.44) | 8.27 (0.44) | 10.32 (0.47) | 10.33 (0.47) | 12.41 (0.49) | 12.42 (0.49) |
Waist circumference, cm (SD) | 57.28 (5.75) | 57.24 (5.92) | 62.38 (7.97) | 61.88 (7.60) | 67.50 (9.49) | 65.94 (9.19) | 72.82 (10.88) | 70.92 (9.81) |
WtHR % (SD) | 46.80 (4.02) | 47.23 (4.28) | 46.48 (5.13) | 46.55 (5.08) | 46.45 (5.79) | 45.28 (5.78) | 45.99 (6.30) | 44.86 (5.93) |
Green space 0–5% | 408 (17.94%) | 361 (16.54%) | 384 (17.91%) | 337 (16.46%) | 366 (17.88%) | 322 (16.43%) | 344 (17.65%) | 312 (16.72%) |
Green space 6–10% | 381 (16.75%) | 371 (16.99%) | 358 (16.70%) | 348 (16.99%) | 339 (16.56%) | 342 (17.45%) | 326 (16.73%) | 329 (17.63%) |
Green space 11–20% | 678 (29.82%) | 652 (29.87%) | 629 (29.34%) | 609 (29.74%) | 598 (29.21%) | 572 (29.18%) | 571 (29.30%) | 540 (28.94%) |
Green space 21–30% | 315 (13.85%) | 346 (15.85%) | 300 (13.99%) | 326 (15.92%) | 287 (14.02%) | 314 (16.02%) | 274 (14.06%) | 300 (16.08%) |
Green space 31–40% | 231 (10.16%) | 204 (9.34%) | 225 (10.49%) | 190 (9.28%) | 217 (10.60%) | 184 (9.39%) | 205 (10.52%) | 172 (9.22%) |
Green space >40% | 261 (11.48%) | 249 (11.41%) | 248 (11.57%) | 238 (11.62%) | 240 (11.72%) | 226 (11.53%) | 229 (11.75%) | 213 (11.41%) |
Weekly income, thousands (SD) | 1.77 (1.17) | 1.77 (1.20) | 2.07 (1.46) | 2.10 (1.51) | 2.25 (1.97) | 2.31 (2.05) | 2.58 (2.00) | 2.52 (1.69) |
Indigenous or Torres Strait Islander (%) | 74 (3.25%) | 79 (3.61%) | 59 (2.67%) | 65 (3.07%) | 56 (2.63%) | 62 (3.05%) | 57 (2.82%) | 56 (2.89%) |
Maternal years education (SD) | 14.58 (2.47) | 14.55 (2.69) | 14.79 (2.46) | 14.73 (2.63) | 14.89 (2.50) | 14.88 (2.62) | 15.05 (2.48) | 15.03 (2.61) |
LOTE (%) | 268 (11.78%) | 249 (11.39%) | 246 (11.12%) | 220 (10.38%) | 224 (10.50%) | 218 (10.71%) | 168 (8.31%) | 159 (8.22%) |
The outcome of the linear regression models for WC can be seen in Table
The influence of green space on children’s waist circumference.
Boys ( |
Girls ( |
|||||
---|---|---|---|---|---|---|
Model 1 | Model 2 | Model 3 | Model 1 | Model 2 | Model 3 | |
Fixed effects | ||||||
Age | 2.53 (2.49, 2.58) |
2.71 (2.60, 2.81) |
2.73 (2.61, 2.85) |
2.21 (2.16, 2.25) |
2.24 (2.13, 2.35) |
2.22 (2.10, 2.35) |
Green space 0–5% | ||||||
Green space 6–10% | −0.31 (−1.46, 0.84) | 1.58 (−0.20, 3.36) | 2.82 (0.86, 4.78) |
0.22 (−0.92, 1.35) | 0.95 (−0.84, 2.74) | 1.64 (−0.31, 3.60) |
Green space 11–20% | −0.61 (−1.63, 0.40) | 1.66 (0.09, 3.24) |
2.30 (0.57, 4.04) |
−0.43 (−1.43, 0.58) | 0.16 (−1.43, 1.75) | 0.86 (−0.89, 2.60) |
Green space 21–30% | −0.86 (−2.06, 0.35) | 2.11 (0.23, 3.98) |
2.51 (0.47, 4.55) |
−0.10 (−1.25, 1.05) | 0.22 (−1.60, 2.05) | 0.44 (−1.53, 2.42) |
Green space 31–40% | −0.27 (−1.61, 1.07) | 0.39 (−1.67, 2.45) | 1.21 (−1.01, 3.44) | 0.29 (−1.04, 1.63) | 0.69 (−1.44, 2.81) | 0.89 (−1.44, 3.22) |
Green space >40% | −1.15 (−2.44, 0.14) | −0.11 (−2.10, 1.87) | 0.09 (−2.12, 2.30) | −0.21 (−1.47, 1.05) | −1.17 (−3.16, 0.83) | −1.54 (−3.71, 0.63) |
Green space |
0.5201 | 0.0775 | 0.0141 | 0.7946 | 0.4356 | 0.0892 |
Green space 0–5% × age | ||||||
Green space 6–10% × age | −0.21 (−0.36, −0.06) |
−0.30 (−0.47, −0.12) |
−0.08 (−0.23, 0.07) | −0.15 (−0.32, 0.03) | ||
Green space 11–20% × age | −0.25 (−0.38, −0.12) |
−0.31 (−0.47, −0.16) |
−0.06 (−0.20, 0.07) | −0.11 (−0.27, 0.05) | ||
Green space 21–30% × age | −0.33 (−0.49, −0.17) |
−0.32 (−0.50, −0.14) |
−0.04 (−0.19, 0.12) | −0.02 (−0.20, 0.15) | ||
Green space 31–40% × age | −0.07 (−0.25, 0.10) | −0.15 (−0.35, 0.04) | −0.04 (−0.23, 0.14) | −0.03 (−0.24, 0.18) | ||
Green space >40% × age | −0.11 (−0.28, 0.05) | −0.11 (−0.31, 0.09) | 0.11 (−0.06, 0.28) | 0.17 (−0.03, 0.37) | ||
Green space × age |
0.0003 | 0.0004 | 0.3054 | 0.0255 | ||
Combined weekly income (thousands) | −0.14 (−0.25, −0.03) |
−0.01 (−0.14, 0.11) | ||||
Child indigenous status | 2.27 (0.25, 4.29) |
3.18 (1.27, 5.09) |
||||
Maternal years education | −0.07 (−0.19, 0.05) | −0.25 (−0.36, −0.14) |
||||
LOTE | 1.25 (0.30, 2.20) |
−0.44 (−1.37, 0.49) | ||||
|
||||||
Random effects | ||||||
Area | 2.25 (0.86, 5.89) | 2.23 (0.85, 5.89) | 2.29 (0.84, 6.20) | 2.48 (1.07, 5.74) | 2.47 (1.07, 5.74) | 1.93 (0.68, 5.46) |
Individual | 50.29 (46.64, 54.23) | 50.34 (46.69, 54.28) | 46.63 (42.91, 50.67) | 43.87 (40.53, 47.49) | 43.87 (40.53, 47.48) | 39.16 (35.87, 42.76) |
Residual | 21.48 (20.73, 22.26) | 21.4 (20.65, 22.18) | 20.31 (19.48, 21.18) | 20.62 (19.88, 21.39) | 20.60 (19.86, 21.37) | 19.91 (19.08, 20.78) |
Multilevel growth curves over age, by green space category (fully adjusted): (a) boys’ waist circumference; (b) girls’ waist circumference; (c) boys’ waist-to-height ratio; (d) girls’ waist-to-height ratio.
The results for WtHR can be seen in Table
The influence of green space on children’s waist-to-height ratio.
Boys ( |
Girls ( |
|||||
---|---|---|---|---|---|---|
Model 1 | Model 2 | Model 3 | Model 1 | Model 2 | Model 3 | |
Fixed effects | ||||||
Age | −4.32 (−6.38, −2.26) |
−4.19 (−6.25, −2.14) |
−3.50 (−5.82, −1.18) |
3.71 (1.59, 5.84) |
3.69 (1.57, 5.82) |
4.66 (2.23, 7.08) |
Age2 | 0.48 (0.25, 0.70) |
0.47 (0.25, 0.70) |
0.41 (0.15, 0.66) |
−0.47 (−0.71, −0.24) |
−0.47 (−0.71, −0.24) |
−0.58 (−0.85, −0.31) |
Age3 | −0.02 (−0.03, −0.01) |
−0.02 (−0.03, −0.01) |
−0.01 (−0.02, −0.01) |
0.02 (0.01, 0.03) |
0.02 (0.01, 0.03) |
0.02 (0.01, 0.03) |
Green space 0–5% | ||||||
Green space 6–10% | −0.31 (−1.05, 0.43) | 0.97 (−0.18, 2.12) | 1.80 (0.54, 3.07) |
−0.11 (−0.83, 0.62) | 0.41 (−0.76, 1.58) | 0.05 (−1.09, 1.19) |
Green space 11–20% | −0.32 (−0.98, 0.33) | 1.02 (0.00, 2.04) | 1.22 (0.10, 2.34) |
−0.38 (−1.02, 0.26) | −0.34 (−1.38, 0.70) | 0.14 (−1.15, 1.43) |
Green space 21–30% | −0.67 (−1.44, 0.10) | 1.19 (−0.02, 2.40) | 1.36 (0.05, 2.67) |
−0.15 (−0.89, 0.59) | −0.02 (−1.22, 1.17) | 0.07 (−1.45, 1.60) |
Green space 31–40% | −0.29 (−1.16, 0.57) | 0.21 (−1.12, 1.54) | 0.55 (−0.88, 1.99) | −0.08 (−0.93, 0.78) | 0.01 (−1.39, 1.40) | −1.20 (−2.62, 0.22) |
Green space >40% | −0.82 (−1.65, 0.01) | −0.46 (−1.75, 0.83) | −0.42 (−1.85, 1.01) | −0.32 (−1.13, 0.49) | −1.10 (−2.41, 0.20) | 0.05 (−1.09, 1.19) |
Green space |
0.4089 | 0.0497 | 0.0096 | 0.867 | 0.3198 | 0.2404 |
Green space 0–5% × age | ||||||
Green space 6–10% × age | −0.14 (−0.24, −0.04) |
−0.21 (−0.33, −0.10) |
−0.06 (−0.16, 0.04) | −0.08 (−0.20, 0.03) | ||
Green space 11–20% × age | −0.15 (−0.23, −0.06) |
−0.17 (−0.27, −0.07) |
0.00 (−0.10, 0.09) | −0.02 (−0.13, 0.08) | ||
Green space 21–30% × age | −0.21 (−0.31, −0.10) |
−0.20 (−0.32, −0.09) |
−0.01 (−0.12, 0.09) | 0.00 (−0.12, 0.11) | ||
Green space 31–40% × age | −0.06 (−0.17, 0.06) | −0.10 (−0.22, 0.03) | −0.01 (−0.13, 0.11) | 0.01 (−0.13, 0.15) | ||
Green space >40% × age | −0.04 (−0.15, 0.07) | −0.04 (−0.16, 0.09) | 0.09 (−0.03, 0.20) | 0.11 (−0.02, 0.25) | ||
Green space × age |
0.0004 | 0.0003 | 0.275 | 0.1082 | ||
Combined weekly income (thousands) | −0.12 (−0.19, −0.05) |
−0.05 (−0.13, 0.03) | ||||
Child indigenous status | 1.83 (0.59, 3.06) |
1.67 (0.46, 2.89) |
||||
Maternal years education | −0.07 (−0.14, 0.01) | −0.18 (−0.25, −0.11) |
||||
LOTE | 0.98 (0.39, 1.57) |
−0.28 (−0.88, 0.32) | ||||
|
||||||
Random effects | ||||||
Area | 1.62 (0.91, 2.88) | 1.62 (0.91, 2.88) | 1.35 (0.68, 2.68) | 1.02 (0.44, 2.34) | 1.02 (0.44, 2.34) | 0.57 (0.15, 2.14) |
Individual | 17.84 (16.50, 19.30) | 17.87 (16.52, 19.32) | 16.52 (15.15, 18.01) | 17.71 (16.35, 19.19) | 17.72 (16.35, 19.20) | 15.72 (14.39, 17.17) |
Residual | 8.99 (8.68, 9.32) | 8.96 (8.64, 9.29) | 8.66 (8.30, 9.03) | 9.12 (8.79, 9.46) | 9.11 (8.78, 9.45) | 8.87 (8.50, 9.26) |
The primary aim of this study was to examine if using different measures of weight status detected different associations between green space and weight status. The results indicated that there is a statistically significant association between green space and changes in both boys’ and girls’ WC and between green space and changes in boys’ WtHR. For both WC and WtHR, children with more green space had lower increase in average WC or WtHRs. This association only manifests, however, when the children were older.
The finding that both WC and WtHR are associated with green space reinforces previous evidence regarding the relationship between green space and BMI. Specifically, the finding that boys’ WC and WtHR are negatively associated with green space indicates that children in low green space areas may be prone to additional visceral fat gain, increasing their risk of future health complications [
Among boys, the results revealed that the greatest differences to the reference category (0–5% green space) by age 13 were seen in the categories with moderate amounts of green space (11–30% green space). No significant effects were noted for either WC or WtHR for those in areas of >30% green space. This nonlinear relationship between green space and children’s weight status has also been noted in research using BMI as a measure of weight status [
The lack of significant associations for girls were also consistent with findings from research using BMI as the measure of weight status [
The strengths of this study include the use of longitudinal data, objective measures of weight status, and an objective measure of green space. Limitations of this study include green space only measuring quantity rather than quality, and at one point in time. The inclusion of data on green space quality may strengthen the findings for areas with high quality green space [
There are a number of important future areas of research into green space influences on health. Most pressing is a greater understanding of the mediating factors which explain any relationship between green space and health. Particular focus should be on examining the causes of the gender differences noted here and in previous research on weight status [
Green space is associated with lower WC and lower WtHR in childhood, particularly for boys. These benefits tended to emerge after the age of 7. With green space being championed by policymakers and planners as central to healthy neighbourhoods, the gender and age-related contingencies observed for child weight status warrant further research.
The findings and views reported in this paper are those of the authors and should not be attributed to DSS, AIFS, or the ABS.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This paper uses unit record data from Growing Up in Australia, the Longitudinal Study of Australian Children. The study is conducted in partnership between the Department of Social Services (DSS), the Australian Institute of Family Studies (AIFS), and the Australian Bureau of Statistics (ABS). The authors also acknowledge the ABS for use of the 2010 mesh block data. Taren Sanders is supported by an Australian Postgraduate Award. Thomas Astell-Burt is supported by a Fellowship with the National Heart Foundation of Australia.