EAL

DM: Prevention of Type 2 Diabetes (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of this study was to determine whether diet and exercise interventions in those with IGT may delay the development of NIDDM, reduce the incidence of NIDDM and thereby reduce the overall incidence of diabetic complications.

Inclusion Criteria:

Impaired glucose tolerance based on 2-hour, 75 g glucose tolerance test using WHO criteria for IGT

Exclusion Criteria:

Individuals were excluded if they did not meet the WHO criteria for IGT.

Description of Study Protocol:

Recruitment:

Half of the clinics (served 126,715 people over 25 years of age) in the Hei Long Jiang province in the northern part of China were selected to participate in a screening study for IGT.

Design:

1. Randomization to 1 of 4 groups by clinic site which included diet, exercise, diet-plus-exercise, and control groups.

2. Baseline exam after 10-12 hr fast:

a. blood pressure, Ht, Wt, Fasting blood glucose and lipids, urine glucose and albumin.

b. questionnaire to assess medical and family history for diabetes

3. Data collected at baseline and every 2 yr

a. OGTT

b. Food intake and physical activity as determined by questionnaire/interviews

Blinding Used (if applicable):

Not mentioned.

Intervention (if applicable):

Intervention: Group sessions: weekly for 1 month, monthly for 3 months, and then every 3 months.

a. Diet:

BMI: <25: 25-30 kcal, 55% - 65% carbohydrate, 10%-15% protein, 25% - 30% fat; instructed to increase vegetables, decrease simple sugars and limit alcohol.

BMI: >25: decrease kcal in order to lose weight at a rate of 0.5-1.0 kg/month to decrease BMI to 23. Individual goals for kcal and daily amounts of foods. Counseling by MD.

b. Exercise: increase leisure physical activity by 1 U/d or 2 U/d if <50 years of age. Unit of exercise consists of 30 min of mild intensity (slow walking), 20 min of moderate intensity (faster walking), 10 min of strenuous intensity (slow running), and 5 min of very strenuous intensity (jumping rope).

c. Diet + Exercise: Individuals received the same instructions as those in the diet only and the exercise only groups.

d. Control: These individuals were exposed to general information about diabetes and IGT. Clinic physicians dispensed informational brochures about diet and physical activity but no individual instruction or formal group counseling sessions were conducted.

Statistical Analysis:

Since randomization was performed by each clinic the data were analyzed in each treatment group by comparing the incidence of diabetes in the clinics assigned to each of the treatments. The Ryan-Einot-Gabriel-Wesch multiple F test was used to compare the clinic groups. Multivariate analysis was performed using Cox's proportional hazards analysis taking into account time of diagnosis. A backwards stepwise procedure was used to identify possible covariates. For analysis of data on exercise and diet, groups were compared using analysis of variance (ANOVA).

Data Collection Summary:

Timing of Measurements:

Data collected at baseline and 2-year intervals (1988, 1990, 1992) over 6 year period.

Dependent Variables:

Incidence of Type 2 diabetes mellitus
Height and weight
Blood pressure
Fasting plasma glucose

Independent Variables:

Diet only
Exercise only
Diet and exercise
Control (information only)

Control Variables:

Description of Actual Data Sample:

Initial N: 577 subjects met criteria for IGT and were randomized.

Attrition (Final N): 530 subjects continued with the study for 6 yr (283 males, 247 females). 29 subjects were lost to follow-up through migration, 7 refused to participate and 11 died.

Age: Mean age of total population was 45.0±9.1

Ethnicity: Not mentioned

Other relevant demographics:

Anthropometrics:

Mean BMI of total population was 25.8±3.8. Mean fasting plasma glucose (mmol/l) was 5.59±0.81 for the total population. Mean 2-hour fasting glucose (mmol/l) was 9.0±0.89 for the total population.

Location: Hei Long Jiang province of China

Summary of Results:

Results at or before

6-year evaluation (n)

Control

Diet

Exercise

Diet +

Exercise

Total

Diabetes by WHO criteria

90 (67.7%)

57(43.8)

58 (41.1)

58 (46.0)

263(49.6)

Fasting hyperglycemia

55 (41.4%)

21 (16.2)

37 (26.2)

33 (26.2)

Other Findings

Each group of clinics providing active treatments differed significantly from the clinics in the control group (P < 0.05). There were no significant differences in incidence of type 2 diabetes by diet, exercise or diet + exercise groups.

The cumulative incidence of type 2 diabetes at 6 yr was 67.7% (95% CI, 59.8 – 75.2) in the control group vs. 43.8% (95% CI, 35.5-52.3) in the diet group, 41.1% (95% CI, 33.4-49.4) in the exercise group, and 46.0% (95% CI, 37.3-54.7) in the diet + exercise group (P<0.05).

When analyzed by clinic, each of the active intervention groups differed significantly from the control clinics (P<0.05) and the differences were similar for those with a BMI <25 and >=25.

In a proportional hazards analysis adjusted for differences in baseline BMI and fasting glucose, the diet, exercise, and diet + exercise interventions were associated with 31% (P<0.03), 46%, (P<0.0005), and 42% (P<0.005) decrease in risk of developing type 2 diabetes mellitus.

There was no difference statistical differences in estimated caloric intake between the groups, however the diet and diet-plus-exercise groups appeared lower. At the 6-year follow-up, average units per day of exercise were significantly higher than at baseline in the exercise and in the diet-plus-exercise groups.

Author Conclusion:

This study has demonstrated in a large group of men and women with IGT that lifestyle intervention over a 6-yr period led to a significant decrease in the incidence of type 2 diabetes mellitus.

Further studies are needed in other ethnic & socioeconomic groups to develop the most appropriate intervention strategies and test the generalizablility of the results.

Funding Source:

Government:

Ministry of Public Health (China), World Bank

Reviewer Comments:

Exercise and diet-plus-exercise groups did not see a lower incidence of diabetes since they had a significantly higher exercise level. Intensity of exercise not mentioned. Intervention included frequent contact for education/support.

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")?	Yes
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?		???
	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?	???
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?	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?	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?	???
	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