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PWM: Physical Activity and Inactivity of Youth (2006)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the prevalence of obesity among sixth- and seventh-grade students in a school-based setting, and to identify known risk factors and additional behaviors hypothesized to be related to developing obesity and type 2 diabetes.
Inclusion Criteria:
None provided
Exclusion Criteria:
  • >14 y (n=5)
  • confined to wheelchair (n=1)
  • non-White, Latino or Asian (n=14, 9 Black, 5 Native American)
Description of Study Protocol:

Recruitment

Letters sent to parents of all 6th/7th grade students at 3 schools to explain study in 2000-2001 school year.

Design

Those that returned consent forms were measured and brief questionnaire (designed to be completed in 3-5 minutes) administered on study days.

Statistical Analysis

  • Correlation coefficients for control variables to ID possible linear associations
  • Means of continuous variables compared by t-tests to ID differences between groups
  • Differences in OB (BMI >95th CDC percentiles) & overweight (>85th) compared with Chi2 or Fisher’s exact tests
  • Logistic regression models for multivariate analysis
Data Collection Summary:

Dependent Variables

  • BMI Z-score (measured ht and wt)
  • % body fat (BIA)

Independent Variables

Lifestyle (18-item questionnaire in Spanish or English)

  1. TV/computer/video hr/d
  2. Sports participation
  3. Walk/bike to school
  4. Who makes meals
  5. Where meals eaten
  6. Regular & diet soda drink intake
  7. Ethnicity
  8. If had T2DM
  9. Rate of weight change

Other Measures:  Glycohemoglobin (finger stick); if high (n=16) given 2-hr OGTT (all normal)

Control Variables

Age, gender, ethnicity

Description of Actual Data Sample:

Initial N: 808 sixth- and seventh-grade students from 3 schools invited to participate

Attrition (final N): 385 (199 females, 186 males; 319 completed short questionnaire (39% of total possible, 77% of consenting), 305 completed final version of questionnaire and reported on herein

Age: 6th-7th grade, 11-13 years, mean = 12.7 years

Ethnicity: 42% Latino, 7.5% Asian/Pacific Islander, 47% White, 3.5% other

Location: Santa Barbara County, CA

Summary of Results:

Prevalence of overweight using BMI:

  • 17.9% 85th-95th percentiles
  • 17.4% >=95th percentile
  • Ethnic differences:  Latino > Asian > White (not clear if significantly different)

Univariate analysis between adiposity and lifestyle factors:

Only 2 factors on questionnaire related to adiposity – TV watching and total soft drinks

TV:

  • Mean BMI Z-score = 0.48 higher (p<.001) for >=2 vs. < 2 hr/day; %Body Fat = 4.9% higher (p <.001) and more likely to have BMI >=85th percentile (47.1% vs. 28.2%, p<.001)
  • TV correlated with BMI (r=.22, p<.001) and %Body Fat (r=.24, p<.001)
  • NS with video games and computer use
  • Ethnic differences:  Latino > Asian & white (p<.001)

Soft drinks (total):

  • Mean BMI Z-score = 0.51 higher for >=3 svgs/d vs. < 3 svgs/d (p=.003); %Body Fat = 4.4% higher and more likely to have BMI >=85th percentile (58.1% vs. 33.2%, p=.006)
  • BMI Z-score and %Body Fat correlated both with diet soft drinks (r=.19, p=.001; r=.18, p=.002) and regular soft drinks (r=.10, p=.08; r=.11, p=.06 [note p values above .05 for sweetened soft drinks])
  • Ethnic differences:  Latino > Asian (p<.001) & White (p<.004)

Multivariate analysis between BMI>85th percentile and lifestyle factors:

  • Both TV and soft drinks significantly related to overweight (even though correlated with each other; r=.27, p<.001) after controlling for age and gender
  • Only total soft drinks remained significantly related after controlling for ethnicity
Author Conclusion:

Time spent watching television and the number of soft drinks consumed were significantly associated with obesity among 6th and 7th grade schoolchildren and can lead to increased risk of developing chronic health conditions, such as diabetes. Latinos spend more time watching television and consumed more soft drinks than did non-Hispanic white or Asian students.  These findings will be beneficial in developing preventive measures for these children.

Funding Source:
University/Hospital: Loma Linda University
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

Strengths:

  • Relatively ethnically diverse sample
  • Questionnaire in English and Spanish

Limitations: 

  • Sweetened soft drinks alone not significantly related to BMI
  • Sweetened and diet soft drinks combined which may relate differently to overweight (cause vs. consequence – cannot tell if kids drink more diet soda and watch more TV because fat or if how they got more fat)
  • Not clear if questionnaire validated for assessing dietary intake and physical activity/inactivity
  • No data on students who chose not to participate
  • Authors considered TV watching related to overweight even though NS after taking ethnicity into account
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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  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? ???
  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? 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? N/A
  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? 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? No
  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? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  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