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NC: Diabetes Management (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

The purpose of the study was to examine the effects of six-month intensive lifestyle modification intervention on metabolic parameters and carotid intima-media thickness (IMT) in patients with Type 2 diabetes mellitus.

Inclusion Criteria:
  • Type 2 diabetes
  • Treated with oral hypoglycemic agents or diet and exercise alone
  • A HbA1c level of 7.0% or higher
  • No change in medication for the past three months
  • No history of ketoacidosis.
Exclusion Criteria:
  • Type 2 diabetes treated with insulin
  • HbA1c below 7.0%
  • Congestive heart failure
  • Recent episode of ischemic heart disease
  • Peripheral vascular disease
  • Current malignancy
  • Chronic renal failure
  • Severe proliferative diabetic retinopathy
  • Any physical or mental conditions that may have an influence on the ability to participate in the intervention.
Description of Study Protocol:

Recruitment

Subjects from the outpatient clinic at Yonsei University Severance Hospital Diabetes Center (Seoul, Korea) with a diagnosis of Type 2 diabetes.

Design

  • Participants were randomly assigned to the intensive lifestyle intervention group or the control group
  • Non-essential changes in medication and dosage that might affect the outcome of the study were not made.

Blinding Used

The readings and analysis of the CCA images were done by a single well-trained physician who was blinded to the identity of the patient, time point and the treatment at the end of the study.

Intervention

  • The goals for the intervention group were to achieve and maintain a modest weight loss (5% of the initial weight in obese subjects), follow a  recommended dietary intake and undertake physical activity of moderate intensity, such as brisk walking for at least 150 minutes per week.
  • A 16-lesson curriculum covering diet, exercise and behavior modification was designed to help the participants achieve these goals. Counseling provided.

Statistical Analysis

  • Baseline comparisons were assessed by independent sample T-tests or x2, as appropriate.
  • Repeated-measures analysis of variance was used to compare the change in fasting plasma glucose, two-hour post-prandial plasma glucose (two-hour PPG) and HbA1c between the groups.
  • Independent T-tests or Mann-Whitney tests were used to analyze the differences between the intervention and control groups in changes from baseline to end-point measurements and changes within the groups were analyzed by paired T-tests  
  • Partial correlation was used to assess the correlation between two variables when adjusting for age and sex
  • Linear regression analysis was used to assess the influence of other baseline demographic or clinical parameters on mean CCA IMT change
  • Statistical analysis of triglycerides, hsCRP, HOMAIR, and HDL-C were performed using log-transformed values because the distribution was not normal
  • Results were considered statistically significant if the P-value was less than 0.05.
Data Collection Summary:

Timing of Measurements

Baseline and six months.

Dependent Variables

  • Fasting blood samples were collected for plasma glucose, serum total cholesterol, serum triglycerides, high-density lipoprotein cholesterol (HDL-C) and HbA1c using standard laboratory techniques
  • Low Density Lipoprotein (LDL-C) was calculated using the Friedewald formula
  • The insulin concentration was measured using a radioimmunoassay kit (DAINABOT, Tokyo, Japan)
  • The homeostasis model assessment of insulin resistance (HOMAIR) was calculated by the following formula: Fasting insulin [uU per ml] x fasting glucose [mmol per L] / 22.5
  • Serum high-sensitivity CRP (hsCRP) levels were measured by a latex-enhanced immunonephelometric assay method using a BN II Nephelometer Analyzer
  • Microalbuminuria was defined as albumin-to-creatinine ratio exceeding 30mg per gram of creatinine in a random urine sample. Urinary albumin was measured by immunonephelometry and creatinine was analyzed by Jaffe reaction.
  • Body weight, height and waist and hip circumference
  • Blood pressure
  • Ultrasonography of the common carotid artery (CCA) was conducted bilaterally by high resolution B-mode ultasonography.

Independent Variables

Baseline and six months.

Control Variables

Type 2 diabetes.

Description of Actual Data Sample:
  • Initial N: 58 subjects (14 male, 44 female)
  • Attrition (final N): 0
  • Age: 54.4 years
  • Ethnicity: Asian
  • Other relevant demographics:
    • Diabetic for 8.8 years
    • HgA1c of 8.8%
    • 76% women
    • 57% were obese
    • 81% of the control were on Biguanides
    • 50% of the intensive group were on anti-hypertensive medications
    • 19% of the intervention and control groups were on lipid-lowering medication.

Anthropometric   Intervention Control   
Weight (kg)

65.7±13.5

66.6kg±13.9
BMI (kg/m2) 25.8±3.8 26.2±4.0

  • Location: Yonsei University Severence Hospital Diabetes Center (Seoul, Korea).
Summary of Results:

 Mean attendance for the 16-week curriculum was 75%.

Changes in clinical and metabolic parameters in the intervention and control groups.

Variables

Treatment Group

 Six Months

Control Group

Six Months

Statistical Significance of Group Difference

Body Weight (kg)

65.7±13.5

 63.7±12.8

66.6±13.9

66.5±14.0

 0.001

BMI (kg/m2)

25.8±3.8

 25.1+3.5

26.2±4.1

26.2±4.2

 0.001

Waist-to-Hip Ratio

0.89±0.05

 0.87±0.05

0.89±0.05

0.88±0.07

 0.74

HbA1c (percentage)

 8.5±1.4 7.6±0.9 8.6±1.3 8.7±1.3 0.002
FPG (mmol/l) 9.1±2.1 7.5±1.5 9.3±1.8 9.6±2.6 0.001
2h PPG (mmol/l) 12.8±3.1 10.7±3.1 13.6±3.7 14.4±4.3 0.005
Total Cholesterol 5.2±1.0 5.0±0.8 4.9±0.9 4.9±0.9 0.36
Triglyceride 1.7±0.8 1.6±0.7 1.8±1.1 2.5±3.3 0.08
HOMAIR 2.6±1.4 2.6±1.5 2.5±1.5 3.2±2.5 0.16
Systolic BP (mm Hg) 130.3±14.5 122.1±11.6 132.7±17.8 133.1±15.1 0.04
Diastolic BP (mm Hg) 84.8±9.5 80.2±8.4 81.1±7.3 80.3±8.4 0.15
HsCRP (mg/L) 0.8±0.8 0.6±0.6 1.3±1.4 1.1±1.1 0.68
Mean carotid IMT (mm) 0.714±0.138 0.664±0.124 0.678±0.205 0.761±0.147 0.007

Other Findings

Multiple linear regression analysis with changes in mean IMT as a dependent variable and baseline clinical characteristics and lifestyle modification intervention as independent variables 

Parameters B P
Sex 0.315 0.15
Age 0.100 0.56
Duration of Diabetes -0.161 0.47
Baseline hsCRP -0.047 0.78
Baseline HbA1c -0.183 0.28
Baseline LDL-C -0.061 0.68
Number of Diabetic Medications 0.222 0.33
Smoking Status 0.141 0.52
Intervention 0.371 0.032

Correlations between change in mean carotid IMT and changes in other clinical parameters (adjusted by age and sex), baseline and six months

Parameters Correlation Co-efficient P-Value   
Fasting Plasma Glucose 0.31 0.045
2h PPG 0.37 0.015
HbA1c 0.34 0.028
LDL-C 0.03 0.87
Systolic Blood Pressure 0.10 0.53
Diastolic Blood Pressure 0.11 0.50
BMI 0.02 0.89
HOMAIR 0.05 0.77

Author Conclusion:
  • An intensive lifestyle modification intervention for six months in Korean patients with Type 2 diabetes mellitus can improve glycemic control, lower blood pressure, promote moderate weight loss and attenuate the progression of carotid IMT
  • A lower HbA1c is associated with a reduced risk of micro-vascular complications and carotid IMT is commonly used as a surrogate marker for artherosclerotic diseases. In this study the changes in mean CCA IMT correlated with changes in HbA1c, fasting plasma glucose and two-hour PPG, suggesting a decreased in the progression of carotid IMT
  • The study limitations of small sample size, participant bias (individuals from an education institution), short intervention and short follow-up period may have affected the findings
  • The findings from this study should be confirmed in an intervention study involving a larger population for a longer study period
  • The author acknowledged the group who provided support for the study.
Funding Source:
Government: NIH
Reviewer Comments:
  • The study was a well-written study which provided a clear explanation of the study objective and findings. I agree with the author's findings and conclusions. The author acknowledged the small sample size, the limited weight loss and the short follow-up period.
  • I am concerned about the quality of the nutrition intervention. There was no dietary information given. I have questions regarding the nutritional content of the recommended dietary intake. I would like to know more specific information about the content of the nutrition counseling. The author mentioned that the energy intake was assessed weekly. He did not mention the results or how they correlated with the weight loss in both groups. A more clearly designed nutrition component may have affected the weight loss differently as well as other clinical measures.
  • It was disappointing to see no mention of a dietitian providing nutritional counseling.
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? No
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) ???
  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? 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
4. Was method of handling withdrawals described? N/A
  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%.) 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? 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
  5.3. 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? 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? N/A
  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? No
  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? Yes
  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? No
  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