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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 investigate prospectively the association between the home environment and socioeconomic factors and the development of obesity in children.
Inclusion Criteria:
0 and 8 years who were enrolled in the National Longitudinal Survey of Youth (NLSY)
Exclusion Criteria:
Not specified
Description of Study Protocol:

Design

Prospective cohort design, examining the relationship between multiple family characteristics and childhood overweight.

Blinding used (if applicable)

NA

Intervention (if applicable)

 None

Statistical Analysis

 Multivariate Logistic Regression Analysis

Data Collection Summary:

Timing of Measurements

Data on children in the NLSY cohort were collected prospectively every 2 years

Dependent Variables

  • Child weight

Independent Variables

  •  Family characteristics (measured using Home Observation for Measurement of the Environment-Short Form (HOME-SF). Survey taken at the time of assessment of weight and height in 1988.

Control Variables

  • Maternal obesity (self-reported height & weight),
  • Initial weight-for-height z-score,
  • Gender,
  • Socioeconomic factors,
  • Race
  • marital status.
Description of Actual Data Sample:

Initial N: 2913  males and females enrolled in the National Longitudinal Survey of Youth (44% were female)

Attrition (final N): 3846 children with growth data available in 1988, 2913 had developed obesity by 1994. 

Age: 0-8 years at beginning of study

Ethnicity: mixed white, African American, Hispanic (dataset seeks to be representative of US population)

Other relevant demographics:

Anthropometrics

Location: USA

Summary of Results:

Maternal Weight

After adjusting for the child's initial weight-for-height z-score:

  • children whose mothers were overweight (25.0 <= BMI < 30.0) had a 1.5-fold increased risk for obesity (P < .01),
  • children whose mothers were obese (BMI >= 30) had more than a threefold increased risk of childhood obesity (P < .001).

Cognitive Stimulation in the Home

Children whose HOME cognitive scores were low or average were significantly more likely to develop obesity compared with children whose HOME cognitive scores were in the upper 15th percentile [(relative risk, low HOME-cognitive: 2.64 [1.48-4.70]), P < .001; medium HOME-cognitive: 2.32 [1.39-3.88], P < .01).

The increased risks of obesity associated with low and average home cognitive stimulation scores were seen consistently across almost all subgroups analyzed. This relationship continued even after multiple other factors were controlled in the multivariate analysis.

Children whose family cognitive environment worsened over the study period were more likley to be obese. About 16% of families had lower cognitive stimulation scores (greater than one standard deviation) in 1994 than 1988.  After adjusting for initial home cognitive scores, these children were significantly more likely to become obese than those whose home cognitive scores did not worsen (relative risk: 1.73 [1.25-2.59]; P < .01).

Television Viewing

Individuals with the highest scores on the HOME cognitive scale watched significantly fewer hours of television per day than children with lower scores (low score, 31.1 hours/week; medium score, 27.5 hours/week; and high score, 21.1 hours/week; P < .001).

However, television viewing itself did not explain the level of cognitive stimulation. After adjusting for the amount of television viewed, increased risks of obesity remained in individuals with low and medium home cognitive scores compared with individuals with high home cognitive scores [(relative risk: low home cognitive, 2.36 [1.30-4.29], P < .01, medium home cognitive, 2.23 [1.33-3.74], P < .01).

Parental Occupation

Children whose parents were either unemployed or whose occupation was nonprofessional were significantly more likely to develop obesity compared with children with a parent in a professional/managerial occupation (relative risk, not used: 2.36 [1.50-4.17], P < .001; nonprofessional: 1.76 [1.15-2.67] P < .01).

Family Structure

Children who lived with single mothers were significantly (P < .05) more likely to develop obesity by the 6-year follow-up,

Maternal Education

children of mothers who did not complete high school were significantly (P < .05) more likely to develop obesity by the 6-year follow-up

Race

Black children were significantly (P < .001) more likely to develop obesity by the 6-year follow-up

Home Emotional Environment

No evidence that the emotional HOME score contributed to the development of childhood obesity.

Author Conclusion:

"We have documented prospectively a greater than twofold increased risk of developing obesity in children with lower cognitive stimulation compared with those having the highest levels of cognitive stimulation. The increased incidence of obesity remained after correcting for maternal obesity, initial weight-for-height z-score, gender, socioeconomic factors, race, and marital status.... This finding is particularly important because minority children and children with lower SES generally have the poorest home environment and the highest levels of obesity."

"An important negative finding of our study is that we did not observe any association between family emotional support and the development of childhood obesity. Children who became obese were equally likely to be hugged, kissed, or spanked as children who did not develop obesity. These results suggest that previous studies that have related neglect to childhood obesity may have been confounded by the effects of low income and low levels of cognitive stimulation."

"Future efforts to prevent childhood obesity should explore whether parental education programs can decrease the prevalence of obesity by encouraging more stimulating home environments in young children."

Funding Source:
University/Hospital: University of Medicine and Dentistry of New Jersey
Reviewer Comments:

Strengths

  • Nationally representative
  • Large data set
  • Instruments were validated

Limitations

  • No measure of father education level
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? Yes
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.) 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? 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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  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? No
  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? 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? 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? Yes
  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? 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