Child Nutrition and Environment
Bell JF, Wilson JS, Liu GC. Neighborhood Greeness and 2 Year Changes in Body Mass Index of Children and Youth. Am J Prev Med. 2008 (Dec); 35 (6): 547-553.
This study was designed to test whether greenness and residential density were independently associated with two-year changes in Body Mass Index (BMI) of children and youth and whether the associations were modified by race or ethnicity, gender, age or socio-economic status.
Electronic medical records of children aged three years to 16 years, who received routine medical care in a primary care clinic network in Indianapolis, IN (Marion County) between 1996 and 2002, who lived at the same address for at least 24 months and who had same-day clinical measurements of height and weight recorded two years apart were included.
Records were excluded if:
- Diagnosis which would bias BMI measurement (e.g., pregnancy, congenital heart disease, cystic fibrosis, cerebral palsy, congenital anomalies)
- Address was less than one km from the county boundary.
Retrospective review of electronic medical records did not require recruitment.
Cohort study comparing Normalized Difference Vegetation Index (NDVI; i.e., Greenness) for address with BMI measurements, age, ethnicity or race, gender and socio-economic status.
- BMI Z-scores were used to capture subtle changes in pooled data over time, with an additional dichotomous variable to categorize expected increase from Time One to Time Two
- Geodata software, Moran's One was used to test spacial auto-correlation of dependent variable (i.e., people of similar weight living near each other, creating biased estimates)
- Stata version 10.0 for ANOVA, multiple linear regression models, F-tests, logistic regression and other comparisons (P≤0.05 significance).
Timing of Measurements
- Electronic Medical Records from 1996 to 2002 were reviewed for patients with at least a 24-month span of living at same address and height and weight data two years apart
- Greenness evaluation from June 6, 2000, was chosen due to low cloud cover and close to peak vegetation growth
- Analysis of data was conducted from 2007 to 2008.
- Body Mass Index (BMI) change (kg/m2)
- Greenness per Normalized Difference Vegetation Index (NDVI).
- Race or ethnicity
- Socio-economic status.
- Initial N: 3,901
- Attrition (final N): 3,831 (51% male)
- Age: Three years to 16 years (median, 9.16)
- Ethnicity: 58% non-Hispanic black
- Other relevant demographics
- 83% on Medicaid
- Obesity: 23%
- Average block group median family income: $36,917 per year (lower than county average of $49,387 per year).
- Anthropometrics: Height and weight measures were used to calculate Body Mass Index
- Location: Marion County, Indianapolis, Indiana, USA.
Key Findings: Linear Regression of Neighborhood Greenness and Residential Density on BMI Z-Scores
Beta-values (95% confidence interval) and P-values (significance ≤0.05).
|NDVI||Residential Density||NDVI + Residential Density|
|Health Insurance (Private: Medicaid)||0.01
|Median Family Income||0.02
|Baseline BMI Z-Score||0.76
|Residential Density||Not applicable||-0.01
NDVI: Normalized Difference Vegetation Index
BMI: Body Mass Index.
- Relationships between NDVI and Time Two BMI Z-scores were significantly modified by insurance status (F-test, P<0.01)
- Higher greenness was associated with lower odds of increasing BMI Z-scores (OR, -0.87; 95% CI, -0.79, 0.97).
- Greenness is inversely associated with BMI Z-scores of children and youth, independent of residential density, gender, age and race or ethnicity
- The promotion and preservation of green space in neighborhoods could be a component of addressing childhood obesity.
|Government:||Agency for Healthcare Research and Quality; Department of Health and Human Services|
- The sample was predominantly African-American and economically disadvantaged. Therefore, we question extrapolation to other groups.
- Statistical analysis was extensive.
Quality Criteria Checklist: Primary Research
|1.||Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)||Yes|
|2.||Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?||Yes|
|3.||Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?||Yes|
|4.||Is the intervention or procedure feasible? (NA for some epidemiological studies)||Yes|
|1.||Was the research question clearly stated?||Yes|
|1.1.||Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?||Yes|
|1.2.||Was (were) the outcome(s) [dependent variable(s)] clearly indicated?||Yes|
|1.3.||Were the target population and setting specified?||Yes|
|2.||Was the selection of study subjects/patients free from bias?||Yes|
|2.1.||Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?||Yes|
|2.2.||Were criteria applied equally to all study groups?||Yes|
|2.3.||Were health, demographics, and other characteristics of subjects described?||Yes|
|2.4.||Were the subjects/patients a representative sample of the relevant population?||No|
|3.||Were study groups comparable?||Yes|
|3.1.||Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)||Yes|
|3.2.||Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?||Yes|
|3.3.||Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)||N/A|
|3.4.||If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?||Yes|
|3.5.||If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)||N/A|
|3.6.||If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?||N/A|
|4.||Was method of handling withdrawals described?||Yes|
|4.1.||Were follow-up methods described and the same for all groups?||Yes|
|4.2.||Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)||Yes|
|4.3.||Were all enrolled subjects/patients (in the original sample) accounted for?||Yes|
|4.4.||Were reasons for withdrawals similar across groups?||Yes|
|4.5.||If diagnostic test, was decision to perform reference test not dependent on results of test under study?||N/A|
|5.||Was blinding used to prevent introduction of bias?||N/A|
|5.1.||In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?||N/A|
|5.2.||Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)||N/A|
|5.3.||In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?||No|
|5.4.||In case control study, was case definition explicit and case ascertainment not influenced by exposure status?||N/A|
|5.5.||In diagnostic study, were test results blinded to patient history and other test results?||N/A|
|6.||Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?||Yes|
|6.1.||In RCT or other intervention trial, were protocols described for all regimens studied?||N/A|
|6.2.||In observational study, were interventions, study settings, and clinicians/provider described?||Yes|
|6.3.||Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?||Yes|
|6.4.||Was the amount of exposure and, if relevant, subject/patient compliance measured?||Yes|
|6.5.||Were co-interventions (e.g., ancillary treatments, other therapies) described?||N/A|
|6.6.||Were extra or unplanned treatments described?||N/A|
|6.7.||Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?||Yes|
|6.8.||In diagnostic study, were details of test administration and replication sufficient?||N/A|
|7.||Were outcomes clearly defined and the measurements valid and reliable?||Yes|
|7.1.||Were primary and secondary endpoints described and relevant to the question?||Yes|
|7.2.||Were nutrition measures appropriate to question and outcomes of concern?||Yes|
|7.3.||Was the period of follow-up long enough for important outcome(s) to occur?||Yes|
|7.4.||Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?||Yes|
|7.5.||Was the measurement of effect at an appropriate level of precision?||Yes|
|7.6.||Were other factors accounted for (measured) that could affect outcomes?||Yes|
|7.7.||Were the measurements conducted consistently across groups?||Yes|
|8.||Was the statistical analysis appropriate for the study design and type of outcome indicators?||Yes|
|8.1.||Were statistical analyses adequately described and the results reported appropriately?||Yes|
|8.2.||Were correct statistical tests used and assumptions of test not violated?||Yes|
|8.3.||Were statistics reported with levels of significance and/or confidence intervals?||Yes|
|8.4.||Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?||N/A|
|8.5.||Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?||Yes|
|8.6.||Was clinical significance as well as statistical significance reported?||Yes|
|8.7.||If negative findings, was a power calculation reported to address type 2 error?||N/A|
|9.||Are conclusions supported by results with biases and limitations taken into consideration?||Yes|
|9.1.||Is there a discussion of findings?||Yes|
|9.2.||Are biases and study limitations identified and discussed?||Yes|
|10.||Is bias due to study's funding or sponsorship unlikely?||Yes|
|10.1.||Were sources of funding and investigators' affiliations described?||Yes|
|10.2.||Was the study free from apparent conflict of interest?||Yes|