Way back in the early 1970s, we started the first community-based prevention program for cardiovascular disease in Finland. While doing it, of course, it was rather natural to pay some attention to diabetes, which is very much linked to cardiovascular disease and is part of a cluster of related disorders. At the time, however, diabetes was much less common than it is nowadays. It was not recognized as a major public health problem, although it was recognized as an important disease to be treated as a clinical entity and an important cardiovascular risk factor. After we did our cardiovascular prevention program, I looked around a little to see what we might be missing. This was the early 1980s when the information available started to indicate that Finland has the highest incidence of type 1 diabetes in the world. And that didn't have any explanation. It still hasn't a full explanation. But it was a very interesting finding and it generated a lot of research in this country, including my own.

  Is that what prompted your review of the worldwide incidence of type 1 diabetes?

As I was working in the field of epidemiology, and with Finland having the highest incidence of type 1 diabetes, I felt the need to properly document how large the geographic differences in incidence really are and what sort of variations we can see worldwide, or within a smaller region like Northern Europe. So I, with my colleagues, put together information that had been fragmented in a lot of different places, and published them together in one article. If the citations are any indication, there was quite obviously a need for such a summary publication.

  Did you follow it up with further research?

In the early 1990s, we initiated a prospective study to look at the changes in the incidence of type 1 diabetes in the world. In 1999 we published another paper in Diabetologia assessing the trends in incidence over time. The original paper in 1994 had the historical data, but a very limited analysis of what happened over time. The 1999 paper contained the time trends, and demonstrated that type 1 diabetes in children is actually increasing throughout the world. Not only here, where the risk is high, but also in very-low-incidence populations such as China and Latin America. Also, my team has coordinated the pooling of the incidence studies worldwide since 1990, including more than 100 populations.

  And what could explain that?

Obviously, it must be partially due to genetic factors and partially due to environmental and lifestyle factors. Certainly something in our environment triggers the disease, but there has to be a genetic susceptibility as well. Without that, diabetes would not develop. That's true for both type 1 and type 2 diabetes. Although it may sound difficult to understand, it looks like the genetic susceptibility is largely responsible for the increase in incidence of type 1 diabetes. Still, 80 years ago, type 1 diabetes was a fatal disease, and insulin replacement therapy was the first experience for human society when people with a fatal disease did survive and reproduce, thus transmitting the susceptibility genes to the next generation. Before insulin, the family line stopped there.

  How do you decide where to send your papers and why did this one go to Diabetologia?

In science, we always want to publish in so-called high-impact journals. The impact factor that one gets from journals like Science or the New England Journal of Medicine are high, but then there are times when one simply wants to make the paper available to the greatest number of researchers in the field. So that's when we might go to a specialized journal like Diabetologia. Then there are other issues: type 1 diabetes, for example, is a common disease in Europe and therefore we would think a European journal might be more appropriate for that kind of research.

  Were you surprised at the impact of the paper?

Not really. When I was planning the paper, I saw a clear need for it. And so I'm not surprised that that need turned out to be real.

  What has to be done now to understand the problem and deal with it?

Regarding type 1 diabetes, we still need considerable research about the role of genes. I think that is most important. We know quite a bit about the susceptibility genes that are involved in the disease process, but still we have to understand how the environment and the genes interact to produce the disease, and then we have to understand how to prevent it. There are some ongoing studies trying to prevent type 1 diabetes, but I think they're still premature. We need to know more before real prevention can be applied. As for type 2 diabetes, it's very clear that prevention through lifestyle modification is the only way to go. And for that we published the first randomized trial data in May 2001 in the New England Journal of Medicine. We showed that lifestyle intervention reduced the risk of type 2 diabetes in high-risk obese individuals by 58%. This was confirmed recently in a U.S. trial, which also demonstrated exactly 58% reduction in the risk of diabetes. The next phase is to start programs nationwide.

  What lifestyle changes are important?

In principle it's very simple: avoid obesity; eat a balanced diet with sufficient macronutrients, fibers, seafood, and healthy oils like olive oil; avoid saturated fats. In addition, sufficient physical activity is very important. Nowadays, what with cars, televisions, and computers, nobody is moving, and that is a major problem. Something needs to be done and something will be done, I'm sure. We also have to do more research to understand the etiology of type 2 diabetes. If we can understand the function of the susceptibility genes for type 2 diabetes and how the disease actually develops, maybe we can use this information to predict who will get the disease and to develop much earlier and more intensive interventions and treatment.

  What do you consider the biggest single challenge in your research?

I think it's what we've just been talking about: to understand how genes and the environment interact to produce type 1 and type 2 diabetes and the complications of diabetes. The disease is severe, but the disease itself is not the big problem. In most patients it can be treated with insulin or oral drugs. We can control diabetes and glucose levels, and new means are coming. The problem is that diabetics develop complications. Basically every organ in the body is affected in the long run. There's heart disease, kidney disease, nerve problems, visual problems, even psychological problems, etc. These can be extremely severe, expensive to treat, and they can shorten life. This is, of course, the biggest challenge. I believe the only way to tackle the complications of diabetes is to prevent the onset of the disease or postpone it so late that it doesn’t really cause any major problem. If people don't get diabetes until they're 75 or 80, then the complications don't have time to develop. It may be that most of the genetically susceptible individuals will eventually develop some degree of diabetes during their lifetime, but the major challenge is to prevent the onset of the disease so we can prevent the complications. For that, we have to understand how the disease develops. This requires knowledge about the genes and the interaction of the genes with the environment. That is, however, a very hard thing to do. It's far more complicated than many researchers and clinicians thought and it requires multidisciplinary approaches.

  Is there a message you'd like to give to the general public about your work?

In general, the most important message is that we have firm evidence now that type 2 diabetes is a preventable disease. So the future looks pretty good for the families at risk for the disease. I think this is very good news and something I'd very much like to get across to the public all over the world.

Jaakko Tuomilehto, M.D., M.Pol.Sc., Ph.D.
Academy Professor
National Public Health Institute
Diabetes and Genetic Epidemiology Unit
Department of Epidemiology and Health Promotion
And Department of Public Health
University of Helsinki
Helsinki, Finland