HbA1c and survival in type 2 diabetes

Among people with type 2 diabetes both high and low blood glucose levels may be associated with increased morbidity and mortality. A retrospective cohort study based on the United Kingdom General 262 Medical Progress June 2010 Global Summaries Practice Research Database has provided more data.

Two cohorts of patients aged 50 years or older with type 2 diabetes were generated from the database. There were 27,965 patients who had changed from oral monotherapy to oral therapy with more than one drug, and 20,005 who had changed to added insulin. The HbA1c level associated with the lowest mortality was around 7.5%. The lowest HbA1c level (lowest decile) of around 6.4% was associated with a 52% increase in mortality compared with the most favourable decile, and the highest decile (around 10.5%) for HbA1c was associated with a 79% increase in mortality above that of the most favourable decile. There was a J-shaped curve for mortality against HbA1c among people on combined oral therapy, and a U-shaped curve among people on added insulin. All-cause mortality was 50% higher among people on insulin-based treatment than among people on combined oral agents.

Both low and high HbA1c levels are associated with increased all-cause mortality in people with type 2 diabetes. Diabetes guidelines may need to be revised to include a minimum value for acceptable HbA1c.

Currie CJ et al. Survival as a function of HbA1c in people with type 2 diabetes: a retrospective cohort study. Lancet 2010;375:481–489; Balkau B, Simon D. Survival in people with type 2 diabetes as a function of HbA1c (comment).