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 relationships between hours of television viewing and adiposity and physical activity among female adolescents, a cohort study with follow-up assessments seven, 14 and 24 months after baseline was conducted.

Inclusion Criteria:

N/A

Exclusion Criteria:

N/A

Description of Study Protocol:

Recruitment

Recruited students from California middle schools from those participating in a history of disordered eating practices.
Only those from the no-intervention groups were eligible for this study.

Design

Trained staff conducted physical and paper-and-pencil assessments over a five-day period.
Follow-up assessments took place approximately seven, 14 and 24 months after baseline.

Statistical Analysis

Cross-sectional analyses: Analyses were performed similarly, but separately for the three dependent variables – SMI-adjusted BMI, SMI-adjusted triceps skinfold thickness and physical activity.
Spearman correlation coefficients were calculated for the associations between baseline hours of reported television viewing and the three DV.

Multiple linear regressions were performed by simultaneously entering the TV viewing variable along with the following potential confounders: Age, race, parent education level and baseline SMI-adjusted BMI for the DV PA; and age, race, parent education level, parent fatness and baseline PA for DVs SMI-adjusted BMI and SMI-adjusted triceps skinfold thickness.

Longitudinal Analyses

Least squares regression lines for changes in SMI-adjusted BMI, SMI-adjusted triceps skinfold thickness and PA as plotted against chronologic age in months.
Longitudinal data on BMI and PA were used to create alternative point-estimates of the DV.
To allow for more direct comparisons with previous work, we performed additional secondary analyses, choosing the 85th percentile of SMI-adjusted BMI and SMI-adjusted triceps skinfold thickness, in the overall sample.
Wilcoxon rank sum test to evaluate univariate association and multiple logistic regression for multivariate analyses mimicking the primary cross-sectional analyses described previously.

Data Collection Summary:

Dependent:

TV viewing.

Independent:

BMI
Tricep skinfold
Level of PA

Control:

Age
Sex
SES: Parent education and income
Sexual maturity (SMI).

Description of Actual Data Sample:

971 middle school (sixth and seventh grade) students were eligible to participate. Students were randomly selected from the no-intervention control group and were included in the longitudinal component.

Final sample: 931 participated at baseline. 19 refused to participate; the remaining missing subjects were absent on the days of the assessment.

The longitudinal analyses sample totaled 536.

Summary of Results:

Reported hours of after school TV viewing and SMI-adjusted BMI were not significantly associated at baseline in univariate (Spearman R=0.053, P=0.17) or multivariate (regression coefficient estimate =-0.067, P=0.86) cross-sectional analyses.

Reported hours of after school TV viewing and SMI-adjusted triceps skinfold thickness were not significantly associated at baseline in univariate (Spearman R=0.005, P=0.90) or multivariate (regression coefficient estimate =-0.190, P=0.67) cross-sectional analyses.

Author Conclusion:

In this large sample of female adolescents, hours of after-school TV viewing was not appreciably associated with BMI, triceps skinfold thickness, level of PA or change in any of these over time.
Important associations between hours of after-school TV viewing and BMI, triceps skinfold thickness and PA were not present in this sample.
It can not be ruled out that there was possible error associated with the measurement of PA or TV viewing, which influenced the ability to detect a stronger effect.

Funding Source:

Government:

NICHD

Reviewer Comments:

The PA and TV viewing measurements may have lacked sensitivity to identify important effects.
Relatively large sample
Longitudinal data.

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)	N/A
	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?	???
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.)	No
	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?	N/A
	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?	No
	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?	No
	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?	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?	N/A
	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?	N/A
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