EAL

NC: Diabetes Management (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The extended follow-up of the Diabetes Prevention Study was designed to assess the long-term results of the lifestyle intervention originally aimed at reducing the risk for developing type 2 diabetes in high-risk individuals.

Inclusion Criteria:

Not discussed in this paper.

Exclusion Criteria:

Not discussed in this paper.

Description of Study Protocol:

Recruitment

Not discussed in this paper.

Design

Randomization started in 1993 and was completed in 1998.
Median follow-up was four years at the end of the study.
Subjects that did not have diabetes at the end of the study were followed for another (median) of three years.

Blinding used (if applicable)

Not applicable to assignment of study group.

Intervention (if applicable)

Intensive Group received intensive diet-exercise counselling.
Control Group received general verbal and written health behavior information without specific individualized advice.

Statistical Analysis

Kaplan-Meier survival curves were calculated to estimate the probability of remaining free of diabetes in the two study groups. The difference between survival curves was tested with the log-rank test.
The Cox proportional hazards model to estimate the hazard ratio for development of diabetes.
All comparisons of endpoints were based on the intention-to-treat principle.

Data Collection Summary:

Timing of Measurements

Annual; post-intervention visits were also annual but no diet or exercise counselling was provided.

Dependent Variables

Diagnosis of diabetes (fasting plasma glucose or 2-hour post-challenge plasma glucose) defined by the WHO 1985 diagnosis criteria.

Independent Variables

Study group assignment
Success of achieving five predefined lifestyle goals

Control Variables

Baseline measures including body weight, nutrient intakes and physical activity.

Description of Actual Data Sample:

Initial N: 522 randomized (265 intervention group/257 control group)

Attrition (final N): After 7 years, 75 in intervention group, 110 in control group

Age: Mean age of all subjects at baseline was 55 years.

Ethnicity: Finnish

Other relevant demographics: There was no significant difference between study groups plasma glucose measurements (fasting and post oral glucose load).

Anthropometrics: Mean body mass index of all sujbects at baseline was 31.1 kg/m².

Location: Finland

Summary of Results:

**Results: Diagnosis of Diabetes**
	Intervention Group	Control Group
Baseline/Randomization	0 (n=265)	0 (n=257)
End of Intervention	44	72
Post-Intervention follow-up	31 new diabetes cases	38 new diabetes cases
TOTAL	75	110
Diabetes Incidence of entire study period of 7 years	4.3 per 100 person years (95% CI 3.4-5.4)	7.4 per 100 person years(95% CI 6.1-8.9)	P=0.0001 log-rank test
Diabetes Incidence of follow-up period only (3 years after intervention)	4.6 per 100 person years	7.2 per 100 person years	P=0.0401 log-rank test

Other Findings

There was a strong inverse correlation between the success score (of achieving lifestyle goals) and the incidence of diabetes during the total follow-up.
Diabetes Incidence of follow-up period only (3 years after intervention) for those subjects that did not achieve any lifestyle goals was 8.0 per 100 person years.
Diabetes Incidence of follow-up period only (3 years after intervention) for those subjects that achieved 4-5 lifestyle goals was 3.8 per 100 person years.

Author Conclusion:

The results of the extended follow-up of the Finnish Diabetes Prevention Study show that the effect of lifestyle intervention on diabetes risk does not disappear after active lifestyle counselling is stopped.

Funding Source:

Government:

Ministry of Education

Industry:

Novo Nordisk (Finland

Pharmaceutical/Dietary Supplement Company:

University/Hospital:

Academy of Finland, University Hospitals of Tampere, Kuopio, Oulu (Finland)

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Previous papers from the Finnish Diabetes Prevention Study reported metabolic measures as change from baseline measures. This paper focused on achievement of lifestyle goals and calculated incidence of diabetes.

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?	???
	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?		???
	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%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	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?		???
	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?		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?	No
	6.6.	Were extra or unplanned treatments described?	No
	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)?	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?	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