Review article on environmental risk factors for type 1 diabetes

Together with colleagues Jill Norris and Randi Johnson in Colorado, Lars C. Stene have written a solicited review article in the March 2020 issue of Lancet Diabetes & Endocrinology (https://www.thelancet.com/journals/landia/article/PIIS2213-8587(19)30412-7/fulltext). They show how dramatically the incidence of type 1 diabetes (T1D) has increased in most parts of the world over the past few decades, and review the evidence from prospective studies on the role of specific non-genetic factors associated with risk of T1D. Many hypotheses exist, but a balanced summary of the existing research allows few conclusions to be drawn. Some factors either show no consistent evidence for association with T1D. Some hypothesized risk factors show no obvious time trends consistent with the changing incidence of T1D, while a few factors such as higher maternal age at birth and childhood obesity seems to be relatively consistently associated with risk of T1D. Nevertheless these associations, while detectable in population samples, are not strong enough to provide meaningful prediction at the individual level or to explain the strong increase in T1D. The authors concluded that we are not able to explain the changing incidence. A novel contribution in this review was data simulations showing that environmental factors will have to be very strongly associated with T1D and at the same time have changed dramatically in the population over the past 50 years, if only one, two or three factors were responsible for the observed change in incidence. It is therefore likely that multiple factors are involved, but the authors also discuss a number of explicit complexities that make it difficult to draw firm conclusions from the existing research in this field.

Lars C. Stene is a senior researcher at the Norwegian Institute of Public Health, Department of Chronic Diseases and Ageing. He is currently a member of the board of Oslo Diabetes Research Centre.