Incidence of Type 2 Diabetes in the Randomized Multiple Risk Factor Intervention Trial

1 March 2005 | Volume 142 Issue 5 | Pages 313-322

Background: Weight loss and increased physical exercise reduce the risk for diabetes in people with impaired glucose tolerance. Randomized trial evidence on the effect of these interventions on people without impaired glucose tolerance is lacking.

Objective: To examine the influence of a comprehensive intervention program on the risk for developing diabetes in men without impaired glucose tolerance and in a post hoc subgroup analysis by baseline cigarette smoking status.

Design: Randomized, controlled trial.

Setting: 22 clinical centers for the Multiple Risk Factor Intervention Trial (MRFIT).

Participants: 12 866 men age 35 to 57 years at risk for cardiovascular disease were randomly assigned to either a special intervention or usual care group and followed for 6 to 7 years; this report focuses on 11 827 men without diabetes or impaired glucose tolerance at entry for whom follow-up glucose measurements were available.

Measurements: Cardiovascular disease risk factors, fasting blood glucose levels, and diabetes medication history were assessed before randomization and annually.

Intervention: Men in the special intervention group were counseled to change diet (reduce saturated fat, cholesterol, and calorie intake), to stop smoking, and to increase physical activity. Blood pressure was treated more intensively in the special intervention group than in the usual care group.

Results: 11.5% of the special intervention group and 10.8% of the usual care group developed diabetes over 6 years of follow-up (hazard ratio, 1.08 [95% CI, 0.96 to 1.20]). The special intervention–usual care hazard ratio for diabetes was 1.26 (CI, 1.10 to 1.45) among smokers (63%) and 0.82 (CI, 0.68 to 0.98) among nonsmokers (37%). These estimates differed significantly (P = 0.0003). Weight gain after smoking cessation and the use of antihypertensive drugs may have counterbalanced the beneficial effect of the lifestyle intervention for the special intervention group smokers, while the lifestyle intervention was beneficial among nonsmokers.

Limitations: Principal findings are based on a post hoc subgroup analysis.

Conclusions: In nonsmokers, an intervention program that included nutrition counseling to produce reductions in weight, serum cholesterol, and (along with antihypertensive medication) blood pressure reduced the risk for diabetes.

*For a complete list of Multiple Risk Factor Intervention Trial investigators, see the following: Multiple risk factor intervention trial. Risk factor changes and mortality results. Multiple Risk Factor Intervention Trial Research Group. JAMA. 1982;248:1465-77. [PMID: 7050440]

Editors' Notes Context Weight loss and exercise decrease the development of diabetes in people with impaired glucose tolerance, but the effectiveness of these interventions in people with normal glucose tolerance is unknown. Contribution Using data from a large randomized, controlled trial of cardiovascular disease prevention in men, the investigators show that participants with normal glucose tolerance at baseline developed diabetes at similar rates whether they received the diet and exercise intervention or usual care. However, the intervention was associated with lower risk of diabetes among nonsmokers. Implications While diet and exercise may reduce the development of diabetes in nonsmokers with normal glucose metabolism at baseline, this benefit was not apparent among smokers. –The Editors

 

Author and Article Information

From the University of Bristol, Bristol, United Kingdom; Minneapolis Medical Research Foundation and University of Minnesota, Minneapolis, Minnesota; The University of Texas Health Science Center at San Antonio, San Antonio, Texas; and the University of Pittsburgh, Pittsburgh, Pennsylvania.

This trial is registered as NCT00000487 on http://clinicaltrials.gov.

Acknowledgments: The authors acknowledge the efforts of the many MRFIT investigators who collected these data and the MRFIT Editorial Committee (Jerome D. Cohen, MD; Jeffrey A. Cutler, MD; Richard Grimm Jr., MD, PhD; Lewis H. Kuller, MD, DPH; James D. Neaton, PhD; Judith K. Ockene, PhD; Ronald Prineas, MD, PhD; and Jeremiah Stamler, MD). The authors thank Dr. Johan Eriksson for information about the percentage of participants who were smokers at baseline in the Finnish intervention study (9).

Grant Support: By National Heart, Lung, and Blood Institute grant R01-HL68140.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: George Davey Smith, DSc, Department of Social Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, United Kingdom; e-mail, zetkin{at}bristol.ac.uk.

Current Author Addresses: Dr. Davey Smith: Department of Social Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, United Kingdom.

Ms. Bracha: Berman Center for Outcomes and Clinical Research, Minneapolis Medical Research Foundation, 825 South Eighth Street, Suite 440, Minneapolis, MN 55404.

Mr. Svendsen and Dr. Neaton: Coordinating Centers for Biometric Research, Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN 55455.

Dr. Haffner: Division of Clinical Epidemiology, Department of Medicine, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284-7873.

Dr. Kuller: The Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261.

Author Contributions: Conception and design: G. Davey Smith, Y. Bracha, J.D. Neaton.

Analysis and interpretation of the data: G. Davey Smith, Y. Bracha, K.H. Svendsen, J.D. Neaton, L.H. Kuller.

Drafting of the article: G. Davey Smith, Y. Bracha, J.D. Neaton.

Critical revision of the article for important intellectual content: G. Davey Smith, K.H. Svendsen, J.D. Neaton, L.H. Kuller.

Final approval of the article: G. Davey Smith, Y. Bracha, J.D. Neaton, L.H. Kuller.

Statistical expertise: Y. Bracha, K.H. Svendsen, J.D. Neaton.

Obtaining of funding: J.D. Neaton.

Collection and assembly of data: J.D. Neaton.