EAL

PWM: Physical Activity and Inactivity of Youth (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the association between race, socioeconomic status (SES) and the prevalence of obesity at baseline in a large cohort of nine- and 10-year-old black and white girls and their mothers or female guardians, participating in the Growth and Health Study
Obesity in black and white girls assessed in relation to various measures of SES and selected environmental factors that included caloric intake and television viewing.

Inclusion Criteria:

Ages nine and 10 years at first clinic visit
Black or white and living in a racially-concordant household
Mothers or female guardians must provide household information.

Exclusion Criteria:

Not applicable.

Description of Study Protocol:

Recruitment

Recruited from schools in Richmond, CA and Cincinnati, OH and from families in a health plan in the Washington, DC area (random sampling from a membership list of families with age-eligible girls). Recruitment of white participants was augmented by Girl Scouts from the Washington, DC area.
Selection of potential public and parochial schools for subjects was based on census tract data that showed equal percentages of black and white children and the least disparity in income and education between black and white residents.

Design

Height and weight measurements were obtained at baseline for the girls and mothers
Caloric intake was assessed by three-day food records which were completed by the girls
Total number of hours of television and videos viewed per week was obtained by a questionnaire, completed by the girls
All measures were gathered during visits to the center and made by certified interviewers and examiners who followed a common protocol.

Statistical Analysis

Associations among ordered categorical and continuous data were examined with Spearman’s rank order correlation coefficient
Significance of racial differences were calculated using Fisher’s Z-transformation of the correlations
To estimate the association of IV with obesity, logistical regression models were used within each race.

Data Collection Summary:

Dependent Variables

Obesity (BMI): Highest quartile (i.e., 75th percentile of BMI for NCHS cohort similar to NHANES II reference criterion; child, more than 20.5kg per m², mother, more than 30.7kg per m²).

Independent Variables

TV viewing: Number of hours per week
Caloric intake: Three-day food record.

Control Variables

SES: Income and mother's education
Number of parents living at home.

Description of Actual Data Sample:

2,379 girls (1,213 black and 1,166 white) ages nine and 10 years and their mothers (includes female guardians)

Summary of Results:

Among white girls, there was an inverse relationship between parental income and education and the occurence of obesity (P<0.001). In black girls, neither income or education were related to obesity.
Number of hours of TV viewing was significantly associated with the prevalence of obesity in both black and white girls, with greater hours of TV viewing associated with higher prevalence to a similar extent among both racial groups (P<0.001)
In the multivariate model, TV viewing remained significantly associated with prevalence of obesity (P<0.001).

Author Conclusion:

Television (TV) viewing is associated with the prevalence of obesity, but due to the stronger negative correlation of TV viewing with both income and education in white girls in contrast to black girls, the relationship between TV viewing and the prevalence of obesity among white girls might have been masked.

Funding Source:

Government:

NHLBI, NIH

Reviewer Comments:

Strengths

Large representative sample
Controlled for SES.

Weaknesses

Generalizability? Mothers were a self-selected group; analysis was limited to those who come in for a clinical assessment.
Measures of income and education are imprecise measures of SES and significance may vary among different ethnic groups
Television viewing as surrogate measure of physical inactivity.

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?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
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.)	Yes
	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?		No
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	No
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.)	No
	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?	N/A
	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?	Yes
	6.6.	Were extra or unplanned treatments described?	???
	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?	Yes
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?	???
	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?	Yes
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