011 HbA1c and mortality in diabetic individuals with heart failure: an observational cohort study

BackgroundControversy exists regarding the importance of glycaemic control in patients with type 2 diabetes mellitus (T2DM) and chronic heart failure (CHF) based on conflicting reports that had used a single baseline HbA1c.ObjectiveTo examine the relationship between the mean of all HbA1c measures after CHF diagnosis and outcome in a large cohort of T2DM patients with incident CHF.DesignRetrospective, observational cohort study.SettingTayside, Scotland.PatientsT2DM patients with incident CHF between 1993 and 2010.MeasurementA weighted mean HbA1c was calculated using all available HbA1c measures following CHF diagnosis and patients were grouped into five categories of HbA1c (≤6%, >6–≤7%, >7–≤8%, >8–≤9% and >9%). We subsequently compared diet and drug treated populations. The relationship between mean HbA1c and all-cause deaths after CHF diagnosis was assessed.Results795 patients with T2DM met study criteria. Median follow-up of 3.8 years saw 491 (61.8%) deaths. Cox regression model, adjusted for all other significant predictors, with the middle HbA1c category (>7–≤8%) as the reference, showed a U shaped relationship between HbA1c and outcome. (6–≤7% [1.29 (1.01 to 1.66)] and >9% [1.38 (1.03 to 1.84)]. We found a similar relationship in the drug treated sub-group. However in the diet only group, low HbA1c was associated with the lowest risk of death (≤7% [0.17 (0.07 to 0.39)]).ConclusionsIn patients with T2DM and CHF, our observational study shows that in drug treated patients there was a U shaped relationship between HbA1c and mortality with the lowest mortality risk in patients with modest glycaemic control (HbA1c, >7–≤9%). However in diet treated patients, lower HbA1c was associated with lower mortality risk.