NC: Diabetes Management (2007)
The Finnish Diabetes Prevention Study was conducted to determine the feasibility and effects of a program of changes in lifestyle designed to prevent or delay the onset of type 2 diabetes in subjects with impaired glucose tolerance.
1. Diagnosis of impaired glucose intolerance based on criteria adopted by the WHO in 1985, which was a fasting plasma glucose concentration of 140 mg/dl or higher or a plasma glucose concentration of 200 mg/dl or higher two hours after an oral glucose challenge.
2. BMI >25
3. 40-65 yr of age
1. previous diagnosis of diabetes mellitus except for GDM
2. involved in regular vigorous physical activity
3. treatment to lower blood glucose
4. chronic disease that would likely limit the ability to continue with the study for 6 yr
5. thyroid or liver disease
6. Psychological or physical disabilities deemed likely to interfere with participation in the study
Recruitment
Subjects were recruited primarily through the screening of members of high-risk groups, such as first-degree relatives of patients with type 2 diabetes
Design
Subjects randomly assigned to control or intervention group.
Control group: At baseline, subjects were given written and oral information about diet and exercise. Additional advice at annual follow-up visits. Analysis of 3-day food diary at baseline and yearly.
Intervention group: Nutritionist gives frequent individualized instruction (7 sessions in year 1; 4 sessions in following years) and group instruction to lower fat intake to <30% of total calories, saturated fat to <10 of total calories, and increase fiber (15g per 1000 calories). Individually guided to increase physical activity: endurance activities (walking, jogging, swimming, aerobic games, skiing) and 2 times/wk supervised resistance training. 3-day food records used for initial counseling and for follow-up every 3 mos throughout the study.
Repeat OGTT yearly for both groups.
Blinding used (if applicable):
The study was only partly blinded. Staff members involved in the intervention had to be aware of study groups, however laboratory staff did not know the subjects' group assignments.
Intervention (if applicable):
Oral glucose-tolerance test, blood pressure, anthropometric measures and 3-day food records were done at baseline and yearly thereafter.
Statistical Analysis
Two-sided t-tests and chi-square tests were used to analyze the differences between the groups at base line and during follow-up. Survival curves were calculated to estimate the cumulative incidence of diabetes. The difference between the groups in the incidence of diabetes was tested by means of the two-sided log-rank test.
To estimate the extent of the dependence of the incidence of diabetes on the changes in lifestyle that were achieved, subjects were given a grade for each goal of the intervention at the one-year visit(with 0 indicating that it was not achieved or 1 indicating that it was achieved). For each sub-group defined according to success score, the proportion of subjects in whom diabetes had developed was calculated. To test for a statistical association between this proportion and the success score, logistic-regression analysis was performed with the use fo the SAS GENMOD procedure.
Timing of measurements
Oral glucose-tolerance test, blood pressure, anthropometric measures and 3-day food records were done at baseline and yearly thereafter.
Dependent variables
- Development of type 2 diabetes mellitus (plasma glucose levels)
- Body weight
- Blood pressure
Independent variables
- Dietary fat and saturated fat intake monitored through food records
- Dietary fiber intake monitored through food records
- Physical activity
Initial N: 523 (172 men;350 women) overweight subjects were recruited for the study.
Attrition (Final N):
40 subjects (8%) withdrew from the study; 9 could not be contacted, 3 withdrew due to serious illness, 1 died and 27 withdrew for personal reasons.
Age: 40-65 years of age (mean age 55±7)
Ethnicity: not provided
Other relevant demographics: Most subjects were first-degree relatives that had diabetes of high-risk groups
Anthropometrics: Mean BMI was 31
Location: Finland
| Variable |
Intervention (N=256) mean±SD |
Intervention 95% CI |
Control (N=250) mean±SD |
Control 95% C |
| Change in weight (% change) | -4.7±5.4 | -5.0 to -4.4 | -0.9±4.2 | -1.0 to -0.8 |
|
Change in plasma glucose (mg/dl) fasting |
-4±12 | -6 to -2 | 1±12 | 0 to 2 |
|
Change in plasma insulin (mg/dl) 2hr after oral glu challenge |
-15±34 | -19 to -11 | -5±40 | -8 to -2 |
|
Change in plasma glucose (mg/dl) fasting |
-2±9 | -3 to -11 | -1±7 | -2 to 0 |
|
Change in plasma insulin (mg/dl) 2hr after oral glu challenge |
-29±64 | -37 to -21 | -11±51 | -18 to -4 |
13 subjects in the intervention group and 48 subjects in the control group did not achieve any of the goals.
Weight loss:
1st year:
- 4.2±5.1 vs. -0.8±3.7 kg in the intervention and control groups, respectively. (P<0.001).
2nd year:
-3.5±5.5 vs. – 0.8±4.4 kg in the intervention and control groups, respectively. (P<0.001)
Plasma glucose concentrations:
1st year:
(fasting: 5.9±0.7 vs. 6.4±0.8 mmol/L, P<0.001; and 2-hr: 7.8±1.8 vs. 8.5±2.3 mmol/L, P<0.05) were significantly lower in the intervention group
2nd year:
(fasting: - 0.1±0.7 mmol/L vs. +0.2±0.8 mmol/L and 2-hr: - 0.8±2.1 mmol/L vs. +0.2.5 mmol/L) were significantly lower in the intervention group. (P<0.001)
Incidence of diabetes:
The cumulative incidence of diabetes after 4 years was 11 % (95% CI, 6-15%)in the intervention group and 23% (95% CI, 17-29%) in the control group and during the study period, the risk of diabetes was decreased
Risk of diabetes incidence was decreased by 58% (P<0.001) in the intervention group and was directly related to changes in lifestyle.
Type 2 diabetes mellitus can be prevented by changes in the lifestyles of high-risk subjects.
It is possible to achieve primary prevention of type 2 diabetes mellitus by means of nonpharmacologic intervention that can be implemented in a primary health care setting. According to our results, 22 subjects with impaired glucose tolerance must be treated in this way for 1-yr or 5 subjects for 5-yr to prevent one case of diabetes.
It is commonly argued that it is difficult to change the lifestyle of obese and sedentary people, but such pessimism may not be justified. The reasonably low dropout rate in our study also indicates that subjects with impaired glucose tolerance are willing and able to participate in a demanding intervention program if it is made available to them.
The time that the nutritionist spent with the subjects was once a year for the control group and in the intervention group: 7 times a year during the first year and 4 times a year thereafter.
If the time spent were 60 minutes times 4 years in the control group, this would be a total of 240 minutes.
For the intervention group, if each encounter were 60 minutes, this would be a total of 360 minutes during the first year and 240 minutes during the 2nd, 3rd and 4th years or a total of 1080 minutes for the protocol.
A cost analysis comparing the cost of medication vs. intervention by the nutritionist would be important as well as the reduced cost of health care by the prevention of type 2 diabetes mellitus.
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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? | ??? | |
| 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? | Yes | |
| 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? | 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? | Yes | |
| 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? | Yes | |
| 6.8. | In diagnostic study, were details of test administration and replication sufficient? | Yes | |
| 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)? | N/A | |
| 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? | N/A | |
| 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 | |