Mixed picture for diabetes mortality trends

By Eleanor McDermid

A large registry analysis shows that younger people may be missing out on a general decline in mortality rates among patients with diabetes.

Overall, the Australian study shows that mortality from all causes, cardiovascular causes and diabetes itself declined among patients with Type 1 or Type 2 diabetes between 2000 and 2011.

"These trends suggest continued success in the treatment of diabetes and its complications", say researcher Jessica Harding (Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia) and colleagues.

However, when the team divided the 1,189,079 study participants, representing 80-90% of Australian diabetes patients, into age categories, they found that some age groups, particularly patients younger than 40 years, missed out on some of these positive trends.

Specifically, patients of all ages with Type 1 diabetes (7.3% of the whole cohort) had significant declines in all-cause and cardiovascular mortality over the study period. But the 16.7% reduction in diabetes-specific mortality in patients aged 0-39 years was nonsignificant, in comparison with significant 27.0% and 70.7% reductions among those aged 40-59 and 60-85 years, respectively.

And among patients with Type 2 diabetes, the youngest patients countered the declining mortality trend in all categories, with a significant 134.4% increase in all-cause mortality and nonsignificant 32.3% and 252.8% increases in cardiovascular and diabetes mortality, respectively.

"[C]ontinued efforts to rectify this disparity are needed", writes the team in Diabetes Care.

The researchers mention several possible reasons for the increased mortality among young patients with Type 2 diabetes, including misclassification of Type 1 and 2 diabetes or a statistical anomaly caused by a small number of events. But given the significant decline in all-cause mortality in young Type 1 diabetes patients, they "believe that the more likely explanation is that young-onset type 2 diabetes represents a more severe form of diabetes."

Harding et al also found that, for most age groups, cancer mortality did not improve during the study period. Rates remained stable (ie, nonsignificant declines) among all age groups of Type 1 diabetes patients and declined significantly among older Type 2 diabetes patients, but Type 2 diabetes patients aged 0-39 years had a significant 179.4% increase.

"[T]he absence of a decline in cancer mortality rates in diabetes is likely to lead to a higher burden of cancer among people with diabetes", say the researchers. "This warrants urgent attention."

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