Primary Prevention of Type 2 Diabetes: Lifestyle Intervention Works and Saves Money, but What Should Be Done with Smokers?

Reducing the risk factors that diseases have in common may prove to be an efficient prevention strategy (1, 2). For example, major risk factors, including obesity, physical inactivity, smoking, hypertension, hyperglycemia, and hyperlipidemia, predict the development of several chronic diseases, such as cardiovascular disease, cancer, diabetes, and dementia (3-5). Although one risk factor may confer a greater risk for a certain disease outcome than another risk factor, these risk factors are correlated and seem to operate in concert. A successful preventive intervention must, therefore, target several risk factors simultaneously (2, 6). This characteristic of preventive interventions means that they are necessarily complex and require considerable resources.

Although several public health interventions have succeeded without a precise understanding of the natural history of the disease and the risk factors' mechanisms of action, we now prefer randomized, controlled trials (RCTs) to demonstrate efficacy. Such trials are often performed in high-risk participants. A high-risk participant often may be defined in several ways, but the high cost of large RCTs may mandate a simple definition that will inexpensively identify participants with a high probability of experiencing a study end point. Previous type 2 diabetes prevention trials have used participants with impaired glucose tolerance (7-11) since their glucose levels are worsening and 30% to 50% of them become diabetic in 10 years (12). Since people with impaired glucose tolerance are already hyperglycemic, we may ask whether high-risk people who have not yet experienced hyperglycemia would be better targets for primary prevention interventions. To date, no trial has been designed to prevent hyperglycemia from occurring, and we must learn from secondary analyses of previous studies.

In this issue, Davey Smith and colleagues (13) present new results from the Multiple Risk Factor Intervention Trial (MRFIT), one of the largest RCTs of a lifestyle …