Pediatric Weight Management

Behavioral Counseling to Reduce Childhood Overweight (2006)

Citation:

DISC. Efficacy and safety of lowering dietary intake of fat and cholesterol in children with elevated low-density lipoprotein cholesterol. The Dietary Intervention Study in Children (DISC). The Writing Group for the DISC Collaborative Research Group. JAMA 1995;273:1429-35.

PubMed ID: 7723156
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To assess the efficacy and safety of lowering dietary intake of total fat, saturated fat, and cholesterol to decrease low-density lipoprotein cholesterol (LDL-C) levels in children.
Inclusion Criteria:
  1. LDL-C >80th & < 98th percentiles for age and gender
  2. 7.8 – 12.1 y for girls, 8.6 – 12.8 for boys (prepubertal)
Exclusion Criteria:
  1. Medical condition or medication that might affect growth or blood cholesterol
  2. Behavior problems in child or family likely to reduce adherences
  3. Onset of puberty
  4. Plans to move within 3 study years
  5. Others described in DISC Collaborative Research Group. Ann Epidemiol 1993;3:393-402)
Description of Study Protocol:

Recruitment

schools, mailings to HMO members, pediatric practices

Prescreening

nonfasting capillary blood total cholesterol >75th age-/sex-specific percentile (4.5 mmol/L)

Screening

average of 2 fasting venous serum LDL-C 80th –98th age-/sex-specific percentile

Randomization

computer-generated randomization assignments balanced by clinical center, group (Intervention or Control), age and gender.

Behavioral intervention

to promote adherence to a diet providing:

  • 28% energy from total fat
  • <8% from saturated fat
  • <9% from polyunsaturated fat
  • <75 mg/1000 kcal per day cholesterol (<150 mg/d)
  • RDA for energy, protein & micronutrients

(Note: similar to NCEP Step II Diet recommended for children with family hx of CHD)

Intervention procedures

  • Theoretical basis:  social learning theory and social action theory
  • Family-oriented & personalized
  • First 6 mo:  6 weekly, then 5 biweekly group sessions + 2 individual visits with child + family
  • Second 6 mo: 4 group session + 2 individual session
  • Second & Third year:  4-6 group + individual sessions + monthly telephone contacts

Usual care (control) procedures

  • Informed if blood cholesterol high at baseline, but not given specific recommendation to see MD
  • Given baseline education publication on heart-healthy eating available to public
  • Given 3-y lipid results and referral letter if warranted

Measurement frequency

baseline, year 1, year 3 (for most variables)

Statistical Analysis: 

  • ANCOVA – to test each of primary hypotheses (LDL-C, height & ferritin) with respect to intervention effect and to test effect on other continuous outcome variables
  • Wilcoxon tests – to test intervention effect on ordered categorical outcomes
  • Potential interactions between treatment assignment and sex were tested and found to be unnecessary
  • Intention to treat analyses – missing year 3 LDL-C data estimated from usual care group distribution; for height and serum ferritin missing values using observed data from group to which participant was assigned; no values impugned for other variables
Data Collection Summary:

Dependent Variables (all measured; no blinding)·

  • LDL-C
  • Total cholesterol
  • HDL-C
  • LDL-C:HDL-C ratio
  • Triglycerides
  • Height
  • Weight
  • BMI
  • Skinfolds (triceps, suscapular, suprailiac)
  • Body circumferences (waist, hip)
  • Blood pressure
  • Ferritin (serum)
  • Folate (RBC)
  • Zinc (serum)
  • Retinol (serum)
  • Albumin (serum)
  • Sexual maturation (Tanner staging)
  • Psychosocial health (Achenbach’s Child Behavior Checklist, Kovacs’ Child Depression Inventory, Spielberger’s State-Trait Anxiety inventory for Children, reading and mathematics subtests of the Woodcock-Johnson Psycho-Educational Batter, Moos’ Family Environment Scale, Eyberg’s Child Behavior Inventory, Sarason’s Life Experience Survey)
  • Diet (3 nonconsecutive 24-hr recalls)

Independent Variables

decreased dietary fat (see above)

Control Variables

  • Baseline value
  • Gender
Description of Actual Data Sample:

Original Sample:

  • >44,000 prescreened
  • 663 prepubertal children (334 I, 329 C) entered study
  • 8-10 y (mean 9.7 y boys, 9.0 y girls)

Withdrawals/Drop-Outs:

(see below; reasons for withdrawal not provided)

Final Sample:

320 (95.8%) I, 303 (92.1%) C at 3-y assessment (ferritin available for 86.2% I and 84.8% C)

Location:  6 clinical centers

  • Johns Hopkins Univ. School of Medicine, Baltimore, MD
  • Northwestern Univ. Medical School, Chicago, IL
  • Univ. of Iowa School of Medicine, Iowa City, IA
  • New Jersey Medical School, Newark, NJ
  • Children’s Hospital, New Orleans, LA
  • Kaiser Permanente Center for Health Research, Portland, OR

Duration:  3 y

Race/Ethnicity:  Not described.

SES:  Not described – but some baseline info given below.

Summary of Results:

Attendance at intervention sessions:  

  • 96% - 1st  6 mo
  • 91% - 2nd  6 mo
  • 91% - 2nd y
  • 89% - 3rd y

Baseline characteristics:

  • No differences between groups in anthropometry, blood lipid levels, blood pressure
  • I group had slightly lower % PUFA intake (p=.03) and slightly higher intakes of vitamin B6 (p=.04) and Zn (p=.02)
  • I group had slightly higher proportion with household income <$20,000 (p=.002)

Dietary Intake:

  • Decreased total fat in both I & C groups
  • Decreases for I > C at 3 y (most adjusted diffs also significant at 1 y, values on Table 1):
    • % total fat difference = -4.2 (95% CI -5.1 to -3.4, p<.001)
    • % SFA difference = -2.1 (95% CI -2.5 to -1.7, p<.001)
    • chol diff (mg/1000 kcal) = -18.1 (95% CI -25.7 to -10.4, p<.001)
    • %MUFA difference  = -1.6  (95% CI -1.9 to -1.2, p<.001)
    • %PUFA difference = -0.3 (95% CI -0.6 to -0.4, p=.03)
    • % protein difference = 0.9 (95% CI 0.4 to 1.4, p=.001)
    • % carbohydrate difference = 3.3 (95% CI 2.2 to 4.3, p<.001)
    • Energy difference (kJ) = -619 (95% CI -923 to -314, p<.001)
  • NS differences at 3 y in intakes:
    • Vitamins A, C, B6
    • Minerals Ca, Fe, Zn (though diff in Zn of –0.6 mg, p=.03 at 1 y)

Blood Lipids: (1 y data Table 2)

  • Decreased LDL-C in both I & C groups
    • Decrease for I > C at 3 y:  adjusted difference (mg/dL) = -3.3(95% CI –6.0 to -0.6, p=.02)
  • Decreased total C in both I & C groups
    • Decrease for I > C at 3 y:  adjusted difference (mg/dL) = -3.3 (95% CI –6.4 to –0.2, p=.04)
  • Mean diff at 3 y in HDL-C – NS
  • Mean diff at 3 y in LCL:HDL- NS
  • Mean diff at 3 y in TG – NS

Anthropometry: (1 y data Table 3)

  • Mean diff at 3 y in height – NS
  • Mean diff at 3 y in weight – NS
  • Mean diff at 3 y in BMI – NS (Mean BMI at baseline = 17.5 ± 2.3 for I, 17.6 ± 2.4 for C)
  • Mean diff at 3 y in sum of skinfolds – NS
  • Mean diff at 3 y in WHR  – NS

Others: NS diff in groups at 3 y

  • Ferritin
  • BP
  • Hg
  • Serum Zn
  • Serum albumin
  • RBC folate
  • Sexual maturation
  • Psychological assessments, except lower Kovak’s Child Depression inventory at 3 y in I group (p=.03)
Author Conclusion:

The dietary intervention achieved modest lowering of LDL-C levels over 3 years while maintaining adequate growth, iron stores, nutritional adequacy, and psychological well-being during the critical growth period of adolescence.

Despite reported lower energy levels in the DISC intervention group, mean weight and height were not different between the groups.  These results suggest underreporting by the intervention group, which is important if it biased the reporting of macronutrients.

Funding Source:
Government: NIDDK, NIH
University/Hospital: DISC Collaborative Reserch Group
Reviewer Comments:

Strengths: Relatively large sample size, well-described protocols, numerous anthropometric, dietary and other measures

Limitations:  Intention to treat analysis for primary variables of interest to author’s, but not for adiposity measures, no blinding of measurements, questionable generalizability to children without elevated LDL-C?, failure to control for all variables that may have been potential confounders

Other Comments:  Primary aim to reduced LDL-C and not adiposity

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
  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) Yes
 
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? ???
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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? ???
  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.) ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
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? ???
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? No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? ???
  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? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  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? ???
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? 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)? 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
  8.7. If negative findings, was a power calculation reported to address type 2 error? ???
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