DM: Prevention of Type 2 Diabetes (2007)
- 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
- 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
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
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
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)
Four-Year Changes in Anthropometric and Metabolic Characteristics by Group
(Participants with incident diabetes were excluded)
Variable |
Intervention Group |
Control Group
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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
Quality Criteria Checklist: Primary Research
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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 | |