Trends in type 2 diabetes

The increasing prevalence of type 2 diabetes frequently makes headline news, apparently pointing towards a failure of prevention strategies. Although incidence and prevalence are still confused in the media—and even in more scientific reporting, Magliano and colleagues’ new systematic review (doi:10.1136/bmj.l5003) of trends in diabetes emphasises that prevalence and incidence data tell very different things about a disease or epidemic.1

Prevalence is important to guide allocation of resources for management, but prevention strategies must be directed against incidence. Effective prevention always reduces incidence (new cases) but won’t necessarily reduce prevalence, which can continue to rise through better treatment and an increase in the number of survivors.

Magliano and colleagues reviewed published data on the incidence of type 2 diabetes over three periods, across more than 100 populations in mostly high income countries.1 They report that although incidence increased consistently until 2005, about one third of more recent studies suggest decreasing incidence and another third suggest stable incidence. The …