PWM: Physical Activity and Inactivity of Youth (2006)
To examine the relationship between obesity, energy intake & physical activity in a large cohort of black & white girls.
- Black or white girls, within 2 weeks of age 9 or 10 years at the time of the first clinic visit,
- Parents of guardians who identified themselves as being of the same race as she was and
- Her parents or guardians completed a household demographic information form and gave informed consent.
Berkeley & Cincinnati sites recruited participants from public & parochial schools that were racially & socioeconmically diverse. Westat recruited participants primarily from the Group Health Association membership listing of families who had girls ages 9-10 years.
Dependent: BMI (height & weight measured following standardized protocol) & Sum of 3 skinfold-thickness measurements.
Independent:
- Total energy intake, total fat intake & % of energy from total fat & saturated fatty acids (consecutive 3-day food records), Physical activity (3-day physical activity diaries & Physical activity patterns questionnaires), Sedentary activity (assessment of # of hours of television & video watched);
- Income (questionnaire) & Level of education (questionnaire).
Control Variables: Race/ethnicity, Age, Income & Level of education.
Statistical Analysis: Multivariate regression analyses analysis.
Original Sample: 2379 black & white girls (1166 white, 1213 black).
Final Sample: 2147 girls (1044 black, 1103 white)
Location: 3 field centers (Berkeley, CA, Cincinnati, OH & Rockville, MD).
Race/Ethnicity: Black & white girls.
SES:
diverse population.Age: 9-10 y.
- BMI & skinfold thickness were highly correlated in this study (r=0.89).
- Compared with white girls, black girls had higher intakes of energy, grams of total fat, & % of energy from total fat. However, black girls had slightly lower intakes of % of energy from saturated fatty acids.
- Multivariate-regression analyses showed that age, number of hours of television & video watched, percent of energy from saturated fatty acids & the activity patterns score best explained the variation in BMI & sum of 3 skinfold-thickness measurements for black girls (R2 for this model – BMI as outcome - was 0.04 (P<0.0001).
- The best model for white girls included age, # of hours of television & video watched & percent of energy from total fat (R2 for this model – BMI as outcome - was 0.05 (P<0.0001).
- (BMI) For both races, total energy intake, total grams of fat intake & the activity diary scores were not found to be significantly & independently related to BMI.
- (Skinfold thickness) For each race the regression models describing the variation in skinfold thickness were similar to those of BMI.
- For both races, total energy, total grams of fat intake & the physical activity diary scores were not found to be independently related to skinfold thickness.
Total Energy:
Total energy intake was not independently & significantly associated with BMI & skinfold thickness in either black or white girls.
Interaction terms:
- Significant interaction term between race & dietary fat in the regression analysis for skinfold led to different regression models for black & white girls.
- It is possible that racial differences in eating patterns result in different sources of fat being prominent in the diet or better identified & quantified by the food record.
Government: | NHLBI |
University/Hospital: | University of California, Berkeley, Children’s Hospital Medical Center, Group Health Association, Maryland Medical Research Institute, |
Strengths
- Large sample size,
- Study sample included both black & white girls.
Limitations
- The median levels of physical activity measured in two ways were not fully consistent with each other.
- High intra-individual variation encountered in dietary estimate.
Quality Criteria Checklist: Primary Research
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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? | N/A | |
3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | N/A | |
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? | N/A | |
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? | 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) | 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? | 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%.) | 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? | 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? | 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? | 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? | 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? | N/A | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | N/A | |
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)? | N/A | |
8.6. | Was clinical significance as well as statistical significance reported? | N/A | |
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 | |