The evidence base for the primary prevention of type 2 diabetes, at least in people who are classified as having impaired glucose tolerance (IGT) is clear and overwhelming 1 . The notion that weight loss, where appropriate, and increased physical activity is beneficial in such persons has long been a belief and is now supported by randomized controlled trial (RCT) studies in many countries. In addition, certain specific pharmacological interventions have also been proven to be effective.The recent RCTs carried out in China 2 , Finland 3 , the USA 4 , Japan 5 and India 6 have conclusively shown that lifestyle interventions in people with IGT can prevent, or at least delay, the transition to type 2 diabetes. These interventions investigated weight loss and increased physical activity in the overweight and obese 3 4 but also lifestyle management in those who were not obese 2 . The pharmacological interventions investigated were medication with the biguanide drug metformin 4 or with the alpha-glucosidase inhibitor acarbose 7 or with sibutramine 8 or, in those with a history of gestational diabetes, troglitazone 9 .
The main features and conclusions of these trials are summarized in Table 1. In the Diabetes Prevention Program (DPP) in the US the risk reduction effect following lifestyle changes were much more apparent than intervention with metformin, which was also significant.
Table 1 | Recent trials relevant to the primary prevention of type 2 diabetes
|
Trial |
Incidence (%) of progression from IGT to type 2 diabetes (intervention vs control) |
Intervention |
|
Da Qing 2 |
44 vs 66 | Lifestyle |
|
TRIPOD 9 |
14 vs 30 | Troglitazone |
|
DPP 4 |
14 vs 29 | Lifestyle |
|
DPS, Finland 3 |
32 vs 42 | Lifestyle |
|
STOP-NIDDM 7 |
32 vs 42 | Acarbose |
|
XENDOS 8 |
6 vs 9 | Xenical |
|
Kosaka et al 5 |
3 vs 9 | Lifestyle |
|
Indian DPP 6 |
39 vs 55 | Lifestyle |
Not shown in the Table is the fact that, for the interventions shown, the number needed to treat (NNT) over three years ranged from 2.25 (Da Qing) to 36 (in the IGT group of the XENDOS study). That is, the number of people needed to be treated with these interventions over three years to avoid one person with IGT progressing to type 2 diabetes ranged from 2.25 to 36 10 .
In the Indian DPP, the effect of following lifestyle changes and intervention with metformin produced similar results as combining both, and did not show an additional benefit (see Figure 1).
Figure 1 | Cumulative incidence of diabetes (%) in the Indian Diabetes Prevention Programme*
*Cumulative incidence of diabetes, calculated using the Cox proportional hazards model. The number of subjects who underwent an annual OGTT was 484, 403 and 345 at 12, 24 and 30/36 months, respectively. The p values for relative risk reduction were as follows: LSM = 0.018, LSM + MET= 0.022, MET = 0.029. LSM and LSM + MET showed identical results, therefore, the graphs overlap.
Source: Ramachandran et al, 2006 6
1.Hamman,RF The Evidence Base for Diabetes Care.In Prevention of Type 2 Diabetes.Chichester: John Wiley and Sons, LTD; 2002.p75-176
2.Pan,X. Li,G. Hu,Y. Wang,J. Yang,W. An,Z. Hu,Z. Lin,J. Xiao,J. Cao,H. Liu,P. Jiang,X. Wang,J. Zheng,H. Zhang,H. Bennett,PH Howard,BV Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance: The Da Qing IGT and Diabetes Study. Diabetes Care.1997; 20: 537-544
3.Tuomilehto,J. Lindstrom,J. Eriksson,JG Valle,TT Hamalainen,H. Ilanne-Parikka,P. Keinanen-Kiukaanniemi,S. Laakso,M. Louheranta,A. Rastas,M. Salminen,V. M,Uusitupa Finnish Diabetes Prevention Study Group Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med.2001; 344: 1343-1350
4.Knowler,W.C. Barrett-Connor,E. Fowler,S.E. Hamman,R.F. Lachin,J.M. Walker,E.A. Nathan,D.M. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med.2002; 346(6): 393-403
5.Kosaka,K. Noda,M. Kuzuya,T. Prevention of type 2 diabetes by lifestyle intervention: a Japanese trial in IGT males. Diabetes Res Clin Pract.2005; 67(2): 152-162
6.Ramachandran,A. Snehalatha,C. Mary,S. Mukesh,B. Bhaskar,A.D. Vijay,V. The Indian Diabetes Prevention Programme shows that lifestyle modification and metformin prevent type 2 diabetes in Asian Indian subjects with impaired glucose tolerance (IDPP-1). Diabetologia.2006; 49(2): 289-297
7.Chiasson,J.L. Josse,R.G. Gomis,R. Hanefeld,M. Karasik,A. Laakso,M. Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomised trial. Lancet.2002; 359(9323): 2072-2077
8.Torgerson,J.S. Hauptman,J. Boldrin,M.N. Sjostrom,L. XENical in the prevention of diabetes in obese subjects (XENDOS) study: a randomized study of orlistat as an adjunct to lifestyle changes for the prevention of type 2 diabetes in obese patients. Diabetes Care..2004; 27(1): 155-161
9.Buchanan,T.A. Xiang,A. Peters,R.K. Kjos,A.L. Marroquin,A. Goico,J. Ochoa,C. Tan,S. Azon,S.P. Protection from type 2 diabetes persists in the TRIPOD cohort eight months after stopping troglitazone.. Diabetes.2001; 50 Suppl 2: A81-
10.Davies,M.J. Tringham,J.R. Troughton,J. Khunti,K.K. Prevention of Type 2 diabetes mellitus. A review of the evidence and its application in a UK setting. Diabet.Med..2004; 21(5): 403-414
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