premise: The number of very young children with diabetes has risen dramatically in the past 20 years. The number of children under 5 who have the type 1 form of the condition has increased fivefold. This dramatic increase is either the symptom of a marked improvement in diagnosis, or because more genetically suscep- tible children are surviving birth and infancy, or it suggests that the environment in which we raise our children has become more dangerous for their future health. The exact cause is unknown, but it is believed to be at least in part inherited. The chances of a child developing type 1 diabetes remains low, but the recent increase is too great to be explained by genetic factors alone. It may be that we are exposing our children to something new and that is the cause, or that we have reduced exposure to something that was preventing it previously.
hypothesis: A plausible explanation of the increase could be that the principal age at which the condition is diagnosed has become lower.