EAL

Child Nutrition and Environment

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the associations of objectively measured characteristics of community design and recreation facilities with objectively measured physical activity of a bi-ethnic sample of adolescents.

Inclusion Criteria:

Participant of a larger cohort designed to periodically follow children starting at age four throughout San Diego County, California
White or Mexican-American race.

Exclusion Criteria:

No objective physical activity measure during the final cohort measurement (mean age 16.2 years)
Valid address not provided at the collection of the final measurement.

Description of Study Protocol:

Recruitment

Four-year-old children were recruited during the mid-1980's from pre-schools located throughout San Diego County, California. The children were periodically followed until final measurements were taken at a mean age of 16.2 years (range 14.6-17.6 years).

Design

Cross-sectional analysis of cohort data

Blinding used

Implied in measurements

Intervention

None

Statistical Analysis

Pearson correlations were computed between all environmental variables and moderate to vigorous physical activity (MVPA) and also BMI.

Significant (or borderline) bivariate correlates were entered in multiple linear regressions to explain MVPA (squared to provide normal distribution) and BMI, with ethnicity and gender as covariates.

Data Collection Summary:

Timing of Measurements

All measurements in the analysis were conducted during the final measurement period concluding the cohort study. Height and weight were measured. BMI was calculated. Physical activity was measured objectively with a uniaxial accelerometer (Actigraph). The Actigraph was worn for a seven-day period. At least four days of monitor data was necessary to be included in analysis. Environmental variables were created in ArcView 3.2. A four-component (land-use mix, retail floor area ratio, intersection density and residential density) walkability index was computed. Two recreation-based environmental variables were computed: One measured the shortest distance to the nearest public or private recreation facility and the other measured the total number of recreation facilities within a buffered area.

Dependent Variables

Measured height, measured weight, calculated BMI
Environmental measures (walkability index)
Proximity to public and private recreation facilities.

Independent Variables

Physical activity (accelerometer)

Other Variables

Gender
Ethnicity.

Description of Actual Data Sample:

Initial N: 98
- 50 boys
- 48 girls
Attrition (final N): 98
Age: Mean age 16.2 years (range 14.6-17.6 years)
Ethnicity:
- 38 white participants
- 60 Mexican-American participants
Other relevant demographics: 41% of mothers reported less than a high school education
Anthropometrics: Mean BMI was 25.5±6.1kg/m²
Location: San Diego, CA, USA.

Summary of Results:

Key Findings

Environmental variables were analyzed looking at three buffered zone surrounding participant's homes. The three zones were 0.25 mile, 0.5 mile and one mile.
Only the 0.5 mile buffered zone yielded significant (or marginal) bivariate correlations with moderate to vigorous physical activity (MVPA) and land-use mix (r=0.285, P<0.004) and walkability (r=0.168, P<0.098)
None of the recreation facility variables (proximity to the nearest recreation facility or the number of recreation facilities in a buffered zone) was related to MVPA
All correlations between environmental variables and BMI were low and non-significant.

Multiple Linear Regression

Separate regressions were conducted for MVPA and land-use mix as well as walkability at the 0.5 mile buffered zone
The stronger results were found for the walkability index. The total model explained 13.5% of the variance in MVPA. All three variables (walkability, gender, ethnicity) each accounted for approximately 4% of the variance.

Other Findings

Median minutes of MVPA were:

31.8 minutes daily for the sample as a whole
37.8 minutes daily for boys
24.8 minutes daily for girls.

Author Conclusion:

Adolescents living in neighborhoods characterized by mixed-use, pedestrian-oriented retail development, connected streets and relatively high residential density were more physically active than those living in less walkable neighborhoods.
Walkability index did not explain a large proportion of the variance in physical activity. Any single factor is expected to be limited in explanatory value due to the large number of correlates of physical activity. The walkability index explained a similar amount of variance as gender and ethnicity.
No associations were found with physical activity and assessment of recreation environment
Small sample limited findings between environmental variables and BMI.

Funding Source:

University/Hospital:

San Diego State University

Reviewer Comments:

Cohort retention (from four years old to final measurements) was poor. Authors compared current sample with 253 children lost to follow-up on baseline data including parent reported marital status, employment status, parent education, household income, number in household and parent's age. Children's gender, age, ethnicity and BMI were also compared. No group differences were found.
Small sample; power necessary is unknown
Data restricted to a small geographic area. Limited in ability to generalize to population of adolescents as a whole.
No data is available regarding the type of physical activity the adolescents participated in or whether physical activity is limited based on environmental factors such as transportation or sociodemographic factors such as cost to participate in organized activities.

Quality Criteria Checklist: Primary Research
Relevance Questions
	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)	N/A

Validity Questions
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?	Yes
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.)	Yes
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	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?		Yes
	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.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	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?	N/A
	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?	No
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?	No
	10.2.	Was the study free from apparent conflict of interest?	Yes