Glycaemic control and the risk of mortality in elderly type 2 diabetic patients (ZODIAC-20)

Abstract

Studies on macrovascular consequences of glucose control in elderly patients (>75 years) with type 2 diabetes mellitus (T2DM) are lacking. The present study aimed to investigate the relationship between HbA(1c) and mortality in this specific population. Between 1998 and 1999, 374 primary care patients with T2DM aged older than 75 years participated in the Zwolle Outpatient Diabetes project Integrating Available Care study, a prospective observational study. Early 2009, data on mortality were collected. Updated means for annually measured HbA(1c) values were calculated after a follow-up time of 10 years. Updated mean HbA(1c) was used as a time-dependent covariate in a Cox proportional hazard model. Main outcome measures were all-cause and cardiovascular disease (CVD) mortality. Analyses were performed in strata according to diabetes duration (<5, 5-11 and ≥11 years). In the group with a diabetes duration <5 years, an increase of 1% in the updated mean HbA(1c) level was associated with an increase in all-cause and CVD mortality risk of 51% (95% CI 17-95%) and 72% (95% CI 19-148%), respectively. Glycaemic control was not related to mortality for patients with a diabetes duration ≥5 years. Poor glycaemic control is related to increased all-cause and CVD mortality in patients >75 years with T2DM of short duration (<5 years). Because of the observational study design, our results should be interpreted with caution. Nevertheless, they are suggestive that improving glycaemic control may be beneficial in elderly patients with T2DM, especially in those with recently diagnosed T2DM. Randomised-controlled trials are necessary to investigate whether this holds true.