EAL

Child Nutrition and Environment

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the relationship between perceived neighborhood safety and overweight status
To assess the validity of reported neighborhood safety among a representative community sample urban adolescents who were racially and ethnically diverse.

Inclusion Criteria:

High school students (grades nine to 12) in selected Boston Public Schools.

Exclusion Criteria:

Classrooms comprised of students with severe cognitive disabilities
Classrooms that listed fewer than five students.

Description of Study Protocol:

Recruitment

In classrooms with total enrollment close to 100, all students were invited to participate.

Design

Cross-sectional study design.

Statistical Analysis

Self-reported height and weight were utilized to compute body mass index (BMI, kg/m²) for adolescents based on CDC growth charts
Chi-square statistics and corresponding P-values were computed to compare perceived neighborhood safety by several associated dimensions
Prevalence ratios (PRs) and 95% confidence intervals (CI) were calculated to examine the association between perceived neighborhood safety and the prevalence of overweight status for relevant covariants and school site.

Data Collection Summary:

Timing of Measurements

The paper-and-pencil survey was administered in the classrooms by trained staff in the spring of the school year.

Dependent Variables

The primary variable was whether adolescents were overweight or at risk of becoming overweight. Body mass index (BMI) was used to classify respondents as underweight, healthy weight, at-risk for being overweight or overweight for using age- and sex-specific BMI cut-offs based on the CDC growth charts from the year 2000. The four-level weight classification variable was subsequently reduced to a dichotomous variable of at-risk/overweight and underweight/normal:

At risk for overweight: Those adolescents were at or above 85th percentile using age- and sex-specific BMI cut-offs based on CDC growth charts from the year 2000
Overweight: Those adolescents were at or above 95th percentile using age- and sex-specific BMI cut-offs based on CDC growth charts from the year 2000.

Independent Variables

Race/Ethnicity:
- Hispanic
- Black
- Non-Hispanic
- White
- Non-Hispanic
- Other
Sex
Age (14 years to 18 years)
Nativity:
- Born in the US
- Born outside the US
Grade:
- Nine
- Ten
- 11
- 12
Adolescents' perception of neighborhood safety: A global perception of neighborhood safety (i.e., "Do you feel safe in your neighborhood?"). The response options for analyses included always, sometimes, rarely or never.
To assess the validity of perception of neighborhood safety, the researchers evaluated the association between perceptions of safety with:
- Beliefs about the seriousness of gang activity in the neighborhood or school
- Having witnessed someone in the neighborhood being attacked with a weapon (other than a gun) in the past 12 months
- Having witnessed someone being physically (i.e., punched, kicked, choked or beaten) in the neighborhood in the past 12 months.

Description of Actual Data Sample:

Initial N: 1,253
Attrition (final N): 1,140
Age: 14 to 18 years
Ethnicity:
- Hispanic: 30%
- Black, non-Hispanic: 46.5%
- White: 13%
- Non-Hispanic, Other: 10.6%
Other relevant demographics: Foreign born (29.8%)
Anthropometrics: At risk or overweight (44.8%)
Location: Boston, MA.

Summary of Results:

Key Findings

More than one-third (35.6%) of students said that they always felt safe, 43.9% said they sometimes felt safe, 11.6% rarely felt safe and 8.9% never felt safe
Those students who reported they rarely or never feel safe in their neighborhoods were more likely than those who said they always or sometimes feel safe to believe that gang violence was a serious problem in their neighborhood or school (68.0% vs. 44.1%, P<0.001) and to have seen someone in their neighborhood assaulted with a weapon (other than a firearm) in the past 12 months (17.8%) vs. 11.3%, P=0.025)
In the fully adjusted model (including grade and school) stratified by race/ethnicity, researchers found a statistically significant association between feeling unsafe in one's own neighborhood and overweight status among those in the "Other" race/ethnicity group [(PR=1.56 (95% CI: 1.02, 2.40)].

Prevalence Ratios (and 95% CI) Estimating Overweight Status Among Students Who Rarely or Never Feel Safe in Their Neighborhood

	Model 1 PR (95% CI)	Model 2^a PR (95% CI)	Model 3^b PR (95% CI)
Hispanic	1.24 (0.98, 1.59)	1.16 (0.91, 1.49)	1.16 (0.89, 1.50)
Black, non-Hispanic	1.09 (0.88, 1.34)	1.10 (0.99, 1.36)	1.10 (0.90, 1.34)
White, non-Hispanic	1.42 (0.82, 2.46)	1.25 (0.71, 2.18)	1.23 (0.85, 1.79)
Other	1.54 (0.90, 2.64)	1.58 (0.91, 2.73)	1.56 (1.02, 2.40)

Note: PR = prevalence ratio; CI = confidence interval. Reference category = students who always or sometimes feel safe in their neighborhood

^a Adjusted for grade level using a generalized linear model.

^b Adjusted for grade level, using a generalized estimating equation model that accounted for clustering by school.

Author Conclusion:

Data suggest that perception of neighborhood safety may be associated with overweight status among urban adolescents in certain racial/ethnic groups
Policies and programs to address neighborhood safety may also be preventive for adolescent overweight
Limitations:
- The cross-sectional data does not inform about the direction of causation (e.g., whether the exposure preceded the outcome)
- The research did not evaluate specific dimensions of neighborhood safety or evaluate objective measures of neighborhood safety
- Self-reported height and weight data for BMI, which has the potential for misclassification because of inaccurate reporting.

Funding Source:

University/Hospital:

Harvard School of Public Health

Reviewer Comments:

A cross-sectional study measures the prevalence of health outcomes or determinants of health, or both, in a population at a point in time or over a short period. However, associations must be interpreted with caution. Bias may arise because of selection into or out of the study population. A cross-sectional design may also make it difficult to establish what is cause and what is effect.
The limitations and critique of the study, as stated by the authors, appear to be very appropriate.

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)	Yes

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%.)	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?	N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	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?	N/A
	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?		N/A
	9.1.	Is there a discussion of findings?	N/A
	9.2.	Are biases and study limitations identified and discussed?	N/A
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