Pediatric Weight Management

Pediatrics and Physical Activity

Citation:

Kimm SYS, Glynn NW, Kriski AM, Barton BA, Kronsberg SS, Daniels SR, Crawford PB, Sabry ZI, Liu K. Decline in physical activity in black girls and white girls during adolescence. N Engl J Med. 2002; 347: 709-715.

PubMed ID: 12213941
 
Study Design:
Longitudinal
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine longitudinal changes in physical activity in a large bi-racial cohort of adolescent girls and examine racial differences and other factors associated with these changes.

Inclusion Criteria:

Enrolled in National Heart, Lung and Blood Institute (NHLBI) Growth and Health Study.

Exclusion Criteria:

None stated.

Description of Study Protocol:

Recruitment

  • Recruited from schools near San Francisco and Cincinnati and a HMO in the Washington, DC area
  • Selection of potential public and parochial schools for subjects was based on census tract data that showed equal percentages of Black and White children and the least disparity in income and education between Black and White residents
  • Subjects from the HMO were randomly selected from a list of eligible families.

Design 

All measures were gathered during visits to the center and made by certified interviewers and examiners, who followed a common protocol.

Statistical Analysis

  • Two sample T-tests, X2 tests, or Wilcoxon two sample tests were used to examine racial differences in descriptive characteristics
  • Race-specific longitudinal generalized estimating equations were used to determine whether changes in activity scores from year one to year five differed from those from year five to year eight
  • Outcome measures were change in HAQ between successive follow-up intervals
  • Predictor variables included income, parental education level, number of parents in the household, BMI and the Habitual Activity Questionnaire (HAQ) score at the outset of each successive follow-up interval.
Data Collection Summary:

Timing of Measurements 

 

Year 1

Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10
Physical Activity Assessment x   x   x   x x x
Anthropometric Measurements x x x x x x x x x x
Socioeconomic Measures x                  
Pregnancy           x x x x x
Smoking Status           x x x x x
School Drop-out Rate             x x x x

Dependent Variable

  • Habitual activity questionnaire (HAQ) scores
    • Validated questionnaire assessing leisure time activities
    • Doesn't include activities performed in physical education classes
    • Physical activitiy was measured as MET-times per week.

Independent Variables

  • Socioeconomic Status
    • Maximal educational achieved by either parent
      • High school or less
      • Some college
      • Four or more years of college
    • Annual income for parents
      • Less than $20,000
      • $20,000 to $40,000
      • More than $40,000.
  • BMI.
Description of Actual Data Sample:

N

2,379 girls.

Age

Ages nine and 10 years (year one) and 18 or 19 years (year 10).

Attrition

At the end of year 10, overall follow-up rate was 89%

  • 91% for Black girls
  • 88% for White girls.

Race/Ethnicity

1,213 Black and 1,166 White girls.

Socioeconomic Status

  • Maximal parental education level
    • High school or less
      • Black girls: 31.6%
      • White girls: 20.3%
      • P<0.001 for comparison with Black girls
    • Some college
      • Black girls: 47.3%
      • White girls: 30.1%
    • At least four years college
      • Black girls: 21.1%
      • White girls: 49.6%
  • Annual household Income
    • Less than $20,000
      • Black girls: 50.5%
      • White girls: 21.1%
      • P<0.001 for comparison with Black girls
    • $20,000 to $39,900
      • Black girls: 27.6%
      • White girls: 30.8%
    • At least $40,000
      • Black girls: 21.9%
      • White girls: 47.8%
  • Number parents in household
    • One
      • Black girls: 43.7%
      • White girls: 18.9%
      • P<0.001 for comparison with Black girls
    • Two
      • Black girls: 56.3%
      • White girls: 81.1%.

Anthropometrics

  • BMI (means±SD)
    • Year one (age nine to10 years)
      • Black: 19.2±4.1
      • White: 17.9±3.3
      • P<0.001 for comparison with Black girls
    • Year three (age 11 to 12 years)
      • Black: 21.5±5.1
      • White: 19.9±4.0
      • P<0.001 for comparison with Black girls
    • Year five (age 13 to 14 years)
      • Black: 23.7±5.8
      • White: 21.6±4.3
      • P<0.001 for comparison with Black girls
    • Year seven (age 15 to 16 years)
      • Black: 25.1±6.4
      • White: 22.7±4.6
      • P<0.001 for comparison with Black girls
    • Year eight (age 16 to 17 years)
      • Black: 25.9±7.0
      • White: 23.1±4.8
      • P<0.001 for comparison with Black girls.

Location

San Francisco, Cincinnati and Washington, DC.

Summary of Results:

Decline in Activity

  • Median activity scores for the whole group decreased by 83% from year one to year 10
  • The decrease in median HAQ scores for Black girls was 100% as compared with 64% for White girls (P<0.001)
  • Mean annual decline in HAQ scores was greater at older ages than for at younger ages
  • Activity levels were lower for Black girls than for White girls even at year one (P=0.008).

Predictors of Decline from Year One to Year Five

  • Parental education was inversely associated with the extent of decline in activity among White girls
  • BMI at baseline was directly associated with declines in activity scores for both races (P=0.006 for Black girls and P=0.03 for White girls)
  • For each additional one unit in BMI, the yearly decrease in activity scores was 0.17 Met-time per week for Black girls and 0.21 MET-time per week for White girls. For each additional one MET-time per week in HAQ scores at the outset, the yearly decline in activity scores, was on average, 0.79 MET-time per week for Black girls and 0.82 MET-time per week for White girls (P<0.001).

Predictors of Decline from Year Five to Year Eight

  • Parental education continued to be  inversely associated with the extent of decline in activity among White girls
  • Living in a single parent household was associated with a greater decline in activity for White girls
  • Higher BMI remained associated with a decline in activity among both Black and White girls (P<0.001)
  • Higher HAQ scores were also associated with a decline in activity (P<0.001) for both groups
  • Pregnancy was associated with a decrease in physical activity among Black girls (P<0.001)
  • Cigarette smoking was associated with a decrease in activity among White girls (P<0.001).  

 

Author Conclusion:
  • Substantial declines in physical activity occur during adolescence in girls and are greater in Black girls than in White girls
  • Some determinants of this decline, such as higher body mass index, pregnancy and smoking, may be modifiable.
Funding Source:
Government: NHLBI
University/Hospital: University of Pittsburgh School of Medicine, Maryland Medical Research Institute, Children's Hospital Medical Center, University of California, Northwestern University Medical School
Reviewer Comments:

Limitations

  • HAQ does not take into account the duration of the activities performed
  • HAQ does not include nonrecreational activities. 

 

Strengths

  • Longitudinal study adequately accounts for Black and White girls' activity and overweight relationship
  • Controlled for SES.
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) Yes
  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) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  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
  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) Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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? ???
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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) 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? No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  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
  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. 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
  5.1. 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? 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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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)? ???
  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)? ???
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  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
  8.6. 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? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
  9. Are conclusions supported by results with biases and limitations taken into consideration? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? N/A
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes