Is the war against type 2 diabetes being won?

Prevention strategies could be contributing to a recent fall in the number of people developing type 2 diabetes in some high income countries, according to a review of the evidence published by The BMJ.

The findings show that after 2005 many populations started to see a decline in the number of people developing diabetes, prompting the researchers to suggest that we may be starting to benefit from type 2 diabetes prevention activities.

But they warn that there is limited evidence from low and middle income countries, where trends in diabetes incidence might be different.

Monitoring of the global diabetes epidemic has mainly focused on diabetes prevalence (number of people living with the condition), which continues to rise. However, this is partly driven by improved treatment and better survival.

In contrast, studies on diabetes incidence (number of newly diagnosed cases) are scarce. Among those that do exist, some report a fall or stabilisation of new cases, but results remain inconsistent.

So a research team led by Dianna Magliano at the Baker Heart and Diabetes Institute in Melbourne, Australia set out to review the evidence on diabetes incidence trends over time.

Their findings are based on published data on the incidence of type 2 diabetes in more than 100 populations in mostly high income countries over five different time periods from 1970-2014.

After taking account of differences in study design and quality, the researchers show that the number of people developing diabetes increased consistently until 2005 (with a peak between 1990 and 1999) but the number of new cases has been generally stable or falling since then.

For example, from 1990 to 2005, diabetes incidence increased in two-thirds (67%) of populations, was stable in 31% and decreased in 2%. But from 2006 to 2014, increasing trends were reported in only a third (33%) of populations, whereas 30% and 36% had stable or declining incidence, respectively.

Countries that showed recent stable or decreasing trends were mainly from Europe and East Asia. However, the researchers say they lacked data from many low and middle income countries, where large increases in incidence could still be occurring.

They also outline some limitations, such as being unable to analyse different sex and age groups separately, and variations in diagnostic criteria for diabetes. Nevertheless their results were largely unchanged after further analysis, suggesting that the findings withstand scrutiny.

As such, they suggest that preventive strategies and public health education and awareness campaigns “could have contributed to this flattening of rates, suggesting that worldwide efforts to curb the diabetes epidemic over the past decade might have been effective.”

Researchers in a linked editorial are cautiously optimistic.

Louise McCombie at the University of Glasgow and colleagues point out that falling or stalling rates “can be deceptive” and that “several potentially confounding factors could further complicate interpretation of the reported trends.”

What’s more, they say social and financial factors “can influence the likelihood that new people with diabetes are identified.”

“While we all long for signs that diabetes is in retreat, this sensibly optimistic systematic review does not provide definitive evidence that true incidence is finally falling,” they conclude.