DM: Prevention of Type 2 Diabetes (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
Purpose of the study was to compare the impact of a 4-year lifestyle intervention on insulin sensitivity and secretion in participants of the Finnish Diabetes Prevention Study. This paper examines changes in insulin sensitivity in a subset of the original subjects who participated in the frequently sampled intravenous glucose tolerance testing.
Inclusion Criteria:
  • impaired glucose tolerance (plasma glucose concentration 140 - 200 mg/dL 2 hours after oral administration of 75 g glucose in patients whose plasma glucose was < 140 mg/dL after an overnight fast
  • middle aged (ages 40 to 65 years)
  • overweight (BMI > 25)
  • participated in the frequently sampled intravenous glucose tolerance testing
Exclusion Criteria:
  • diagnosis of diabetes mellitus
  • chronic disease condition
  • other characteristic that would be likely to interfere in study participation (psychological or physical disability)
  • did not participate in the frequently sampled intravenous glucose tolerance testing
Description of Study Protocol:

Recruitment - subjects were recruited primarily through screening of high-risk persons who were first-degree relatives of patients with type 2 diabetes, overweight persons with BMI of > 25, or middle aged persons with glucose intolerance.

Design - RCT

Blinding used- no blinding

Intervention- 

  • intervention group received detailed, individualized advice about weight loss and increasing physical activity; they had seven sessions with a clinical nutritionist during year one of the study, then were seen quarterly; they also had individual guidance on increasing physical activity which included endurance exercises and circuit-type resistance training
  • at an annual visit, the control group received general advice about healthy food, importance of weight loss and increasing physical activity to reduce risk of type 2 diabetes mellitus; if a condition such as high cholesterol was discovered at the annual visit, they were referred to their personal physicians for care

Statistical Analysis

  • Kolmogorov-Smirnov test with Lilliefors correction for continuous variables that wre normally distributed
  • Logarithmic transformation for variables not normally distributed
  • Univariate ANOVA  adjusted for age, sex, BMI, and baseline glucose sensitivity
  • Multiple regression analyses used to assess predictive factors of change in insulin sensitivity
  • Paired and unpaired t-tests used when applicable
  • Significance level set at P <  0.05
Data Collection Summary:

Timing of Measurements

Anthropometric and metabolic characteristics at baseline and 4 years (weight, BMI, waist circumference, fasting glucose, 2-hour glucose, fasting insulin, 2-hour insulin, HbA1C, acute insulin response (AIR), glucose effectiveness (Sg) and insulin sensitivity (Si).

Dependent Variables

  • change in weight (pounds at baseline minus pounds at 4 years)
  • change in BMI (BMI at baseline minus BMI at 4 years)
  • change in waist circumference (cm at baseline minus cm at 4 year)
  • change in fasting glucose (mmol/L)
  • change in 2-hour glucose (pmol/L)
  • change in HbA1C (%)
  • change in acute insulin response (mU*1-1*min-1).
  • change in glucose effectiveness (X10-4 * min-1 * uU-1 * m-1)
  • change in insulin sensitivity ([min]-1 * 102)

Independent Variables

  • intervention (diet and physical activity) versus no intervention 

 

Description of Actual Data Sample:

Initial N: (87 (gender of this subset of subjects not described)

Attrition: Final N= 52

Age: mean age 55

Ethnicity: Finnish

Other relevant demographics:

Anthropometrics and Metabolic Measures

  • groups were not significantly different on important measures of age, BMI, waist circumference, hip circumference, plasma glucose

Location: Helsinki, Finland (1993 - 2000)

 

Summary of Results:

 

 Four-Year Changes in Anthropometric and Metabolic Characteristics by Group

(Participants with incident diabetes were excluded)

Variable

Intervention Group


Control Group
  n= change after 4 years P Value n= change after 4 years P Value

weight (kg)

31 -4.9 ± 4.9 < 0.001 21
-1.4 ± 5.5
< 0.001

BMI (kg/m2)

31

  -1.8 ± 1.9

<0.001 

21 -0.5 ± 2.0
0.227

waist circumference (cm)

 31

 -4.8 ±5.2

 < 0.001

20 -1.8 ±4.5 0.096
fasting insulin (pmol/L) 29 -15.4 ± 27.0
0.001 20 -25.7 ±60.3 0.086
acute insulin response (mU*1-1*min-1). 31 -27 ± 162 0.281 21 -66 ± 107 0.011

Multvariate analyses revealed that changes in body weight and insulin sensitivity were highly correlated (r=-0.626 intervention group and r=0.710 control group). When weight loss was categorized by tertile:

  • Tertile 1 (weight change of -8% to -17%): 64% improvement in insulin sensitivity
  • Tertile 2 (weight change of -7.9% to -1.5%): 12% improvement in insulin sensitivity
  • Tertile 3 (weight change of -1.4% to +10.0%): 24% decrease in insulin sensitivity


 

Author Conclusion:
Healthy lifestyles that include weight loss and increase in physical activity lead to improvement in insulin sensitivity in overweight subjects who are insulin-resistant.
Funding Source:
Reviewer Comments:
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) 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? 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? 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? Yes
  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? 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.) 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? 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? 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
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)? No
  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