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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 overweight among kindergarten-age predominantly Mexican American children in two Chicago, Illinois, elementary schools and to describe he relationship between child and family factors – including acculturation – and overweight in those children.
Inclusion Criteria:
None provided.
Exclusion Criteria:
1 of 2 siblings (randomly selected) from interviewed mother excluded from analysis.
Description of Study Protocol:

Recruitment

All kindergarteners from 2 inner-city public schools invited to participate Sept – Nov 1996 (convenience sample).

Statistical Analysis

  • Representatively of maternal sample – Chi2 and t-tests
  • Comparisons of overwt and nonoverwt children – t-test, Mann-Whitney, Fisher exact and Chi2
  • Relationship between control variables – Spearman’s or Pearson’s correlation coefficients
  • Accuracy of mothers’ perception of own wt category – Kappa statistics
  • Identification of factors related to child overweight status – logistic regression models, forward stepwise method with variables entering and remaining in model at p<.05, and interaction terms examined; 3 factors considered in models: TV viewing on weekends (>3 vs. >=3 hr/d); sweetened beverage intake (daily vs. < daily); maternal perception of their own weight (normal or low vs. overwt or very overwt)
  • Identification of factors related to child wt-for ht percentile – 1-way ANOVA
Data Collection Summary:

Dependent

  1. Overweight status in children (measured weight for height; measured by same MD or RD) defined as =95th percentile (CDC growth charts )
  2. Weight/height percentiles in children

Independent

Lifestyle and demographics (81-item questionnaire in Spanish; developed from existing tools whenever possible; test-retest reliability not assessed because of low response rate):

  1. Physical activity (>3 hr/d spent in outdoor activities, number of months parents participate in outdoor activities with children, number of days/week parents participate in outdoor activities
  2. TV watching (weekdays & weekends > 3hr)
  3. Sleep duration (hr/d)
  4. Infant toddler feeding practices (ever breastfed, age of introduction of solids, age of bottle weaning)
  5. Eating habits of children (FFQ type question on sweetened beverages (powdered drinks, soda, atole, excluding fruit juice), drinks milk every day, if whole milk, daily milk intake, if calorie-containing additives added to milk, daily fruit juice consumption, mother prepares food in style of country of origin, child preference of food in style of country of origin
  6. Weight perception and perceived self-control over body weight
  7. Psychosocial family characteristics

Other Measures: (same questionnaire as described above)

  1. Age (school records and questionnaire)
  2. Other demographics including child gender & country of birth, mother’s age, race/ethnicity, education, marital status, country of birth, financial aid programs)
  3. Acculturation (language, media use, social relations, country of birth of parents and grandparents)
  4. Overweight status in mothers (measured) defined as BMI 25-29.9; Obesity defined as BMI>=30

Control Variables

None per se (but see multivariate analysis below for variables entered together in model).

Description of Actual Data Sample:

Initial N: 271 children (from 270 families)

Attrition (final N): 250 children (92%) measured; 80 mothers (32%) interviewed on risk factors; 38 mothers measured

Age: Kindergarten, 5-6 y

Ethnicity: 100% Hispanic (primarily Mexican American)

Other relevant demographics:

SES: 79% moms and 19% kids born in Mexico; 70% moms married; 71% moms <12 y education; 81% families received public aid

Location: Chicago, IL

Summary of Results:

Representativeness of subsample:

  • Children with vs. without interviewed mothers:  similar on gender, mean weight, prevalence of overweight, mean weight for height percentile
  • Median age older with interview (5.5 vs. 5.2 years, p<.05); but not clinically different
  • Mean height lower with interview (112 vs. 114 cm, p=.02)

Prevalence of overweight: 

  • 23% total sample overweight
  • 26% of sample with mom’s interviewed overweight
  • Prevalence similar by demographic characteristics
  • Only 40% of mothers with overweight child correctly assessed child’s weight status
  • 43% mothers were overweight, 44% were obese
  • 60% of normal weight mothers and 76% of overweight/obese mothers correctly classified own weight status

Univariate analysis:

  • Acculturation score: NS with weight/height percentile
  • TV watching on weekend days: + association with overweight (48% overweight children watched  =3 hr /d vs. 22% non-overweight, p=.03)
  • Sweetened drinks: + association with overweight (67% overweight children drank daily vs. 39% non-overweight, p=.03)
  • Free access to food at home: trend toward positive association (86% overweight children vs. 74% non-overweight, p=.06)

Multivariate analysis: (weekend TV,  sweetened drinks, mom’s perception of own weight)

  • Child overweight status: only sweetened beverage intake (adjusted OR 3.7, 95% CI 1.2-11.0 for daily vs. <daily intake) and mom’ perception of own weight (adjusted OR 5.9, 95% CI 1.2-29.0 for perceived overweight vs. not) remained related
  • Child weight/height percentile: only TV viewing on weekends (explaining 4% of variance, p=.04) remained related
Author Conclusion:

Approximately one quarter of this group of predominantly Mexican American preschool-aged children were overweight. Our hypothesis that their obesity was linked to acculturation was not confirmed.  Longer hours of child television viewing on weekends and higher levels of sweetened beverage consumption were important behaviors associated with the occurrence of overweight.  These may be alterable contributors to the development of overweight in Hispanic children.  Many mothers did not accurately perceive when their children were overweight.  Because the factors that differed substantially between the overweight and nonoverweight children in the study explained only a very small proportion of the variation in children’s weight, the search must continue for multiple weaker – and perhaps previously unrecognized strong – explanatory factors.

Funding Source:
University/Hospital: Children's Memorial Hospital
Reviewer Comments:

Strengths:

  • Focus on Hispanic children for which little risk factor literature is currently available
  • Examined acculturation.

Limitations:

  • Small number of mothers participated (in questionnaire or measurements)
  • Small sample size => limited statistical power
  • Possible response bias – children with and w/o interviewed mother may not be comparable on important variables of interest
  • Not clear if questionnaire validated for assessing dietary intake and physical activity/inactivity
  • Exact amount of TV viewing not assessed and only weekend viewing in multivariate models
  • Volume of beverage intake not assessed (only frequency of consumption assessed)
  • Not clear how why included only 3 variables in multivariate analysis and how these were chosen
  • No control for potential confounders

Other Comments:

Fruit juice not defined; inclusion of "fruit drinks" unknown, but fruit juice does not include sweetened beverage such as Kool-Aid, fruit punch or “atole” a typical Mexican sweetened drink).  Because investigators did not separately assess the volume of juice or sweetened beverage intake, this study does not add to the current controversy regarding the contribution of fruit juice intake to childhood obesity.
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? No
  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? No
  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? No
  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? No
  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)? No
  8.6. Was clinical significance as well as statistical significance reported? No
  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? ???
  10.2. Was the study free from apparent conflict of interest? Yes