DM: Prevention and Treatment of CVD (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To compare the dietary energy (kilocalories), the intake of macronutrients and micronutrients, of folate, and vitamins B6 and B12, as well as the serum lipid profiles and tHcy levels for adolescents with type 1 diabetes, type 2 diabetes, and healthy non-diabetic conrols.
Inclusion Criteria:

Kamath study:

  • age between 13 and 19
  • no known conditions requiring diet modifications
  • no history of diabetes, CAD, kidney or liver disease, or cancer of any kind

Faulkner study:

  • diagnosis of diabetes for at least one year
  • no other chronic conditions
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

  • Kamath study:  nondiabetic subjects recruited from a high school in an affluent Chicago suburb
  • adolesecents with type 1 or type 2 diabetes recruited from a pediatric diabetes clinic at a major medical center in Chicago

Design : 

  • data from two separate studies (Kamath et al and Faulkner et al) were merged and used for cross-sectional analysis
  • subject in the Kamath study completed a personal and family medical history form

Blinding used (if applicable):  not applicable 

Intervention (if applicable):  not applicable 

Statistical Analysis

  • 2-tailed tests of significance at an alpha level of .05
  • one-way analyses of variance with subsequent post hoc Tukey tests used to test for significant differences among the mean comparisons of height, weight, BMI, dietary energy, macronutrient intake, selected micronutirent intake, and serum concentrations of lipids, lipoproteins, and tHcy for males and for females across the 3 groups: type 1, type 2, and non-DM
  • stepwise regression analyses were completed to identify models for prediction of plasma tHcy concentration or lipid profiles based upon age, gender, and BMI for each of the groups
  • Pearson correlation coefficients used to determine relationships among dietary folate, vitamins B6 and B12, and tHcy for each of the 3 groups.
  • Pearson correlation coefficients computed to determine relationships among duration of diabetes or metabolic control with tHcy and lipid profiles in those with type 1, type 2 DM, and both types combined.

 

Data Collection Summary:

Timing of Measurements: measurements taken once

Dependent Variables

  • total cholesterol, triglycerides, HDL, LDL, HbA1c
  • tHcy

Independent Variables

  • height and weight; BMI
  • nutrient and energy intakes, assessed by 3-day 24-hour food records
  • duration of diabetes

Control Variables

  • gender, height, weight, BMI
  • energy intake, macronutrient intake, selected micronutrient intake
  • serum concentrations of lipids, lipoproteins, and tHcy

 

Description of Actual Data Sample:

Initial N: 117 adolescents; 49 males

Attrition (final N): as above

Age: 13-18.9 years

Ethnicity: 64 subjects were black, 2 were Hispanic, 24 were Asian

Other relevant demographics:

  • 53 non-DM, 50 type 1 DM, and 14 type 2 DM
  • the type 1 subjects were significantly younger and shorter

Anthropometrics

  • subjects with type 2 DM were significantly heavier

Location: United States

 

Summary of Results:

 

Variables

 Males

    Females  

 

  Non-DM Type 1 Type 2 Non-DM Type 1 Type 2

Total Cholesterol, mg/dl

 156±6 163±5 176±16 164±5 174±81  168±12

Triglycerides, mg/dl

 105±10

60±7b 120±32a 82±5 76±13

87±28 

HDL, mg/dl

 48±3

50±2 45±4 54±2 54±3

53±4 

LDL, mg/dl  89±5 101±4 106±9 93±4 105±6 97±10 
total homocysteine, micromol/l  7.3±0.4a 5.1±0.3b 8.1±2.1a 6.2±0.3a 4.8±0.2b 5.7±0.2a,b 

 Values within a row for each gender with different superscripts are significantly different at P<.05

Other Findings

Diet

  • CHO intake was significantly lower in subjects with type 1 DM
  • subjects with type 2 DM had significantly higher intakes of saturated fat
  • female diabetic subjects had significantly higher total fat intakes compared to non-diabetic subjects

tHcy

  • no relationship between tHcy and HbA1c in youth with type 1 or type 2 DM
  • In type 2 subjects, tHcy was related to total cholesterol (r = 0.65, P= 0.01) and triglycerides (r= 0.68, P= 0.008)

lipid profiles

  • higher levels of HbA1c were related to total cholesterol (r=.030, P= 0.03) and triglycerides (r=0.28, P= 0.05) in type 1 patients

 

Predictors of Lipoproteins in Adolescents with Diabetes and Healthy Controls

Group Predictor Lipoprotein Beta R2 Adjusted R2 P
Non-DM BMI Triglycerides 0.33 0.11 0.09 .02
  BMI LDL 0.30 0.09 0.07 .03
Type 1 DM Age Triglycerides 0.40 0.16 0.15 .004
  Age LDL 0.33 0.11 0.09 .02
type 2 DM Age LDL 0.57 0.32 0.27 .03

 

Author Conclusion:
  • adolescents with type 1 DM had the lowest tHcy levels (P<.05)
  • lipid profiles and energy intake did not differ significantly among the 3 groups
  • HbA1c was related to total cholesterol and triglycerides in those with type 1 DM, confirming the importance of promoting better metabolic control in lipid management for these youth.
Funding Source:
Reviewer Comments:

The youth with diabetes had a wider income range (less affluent) compared to the non-diabetic subjects.

Biochemical assays for the non-diabetic students were taken in some situations by the school nurse.

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? 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? No
  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? 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.) Yes
  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? N/A
  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? N/A
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  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? 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? Yes
  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? 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? No
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? No
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