New-onset diabetes in elderly subjects: association between HbA1c levels, mortality, and coronary revascularization

Abstract

Objective: New-onset diabetes mellitus (DM) in elderly patients is associated with increased risk of diabetes complications and mortality. It is unknown whether glycemic control in this population influences the mortality risk.

Research design and methods: The current study was conducted using the computerized database of the Sharon-Shomron District of Clalit Health Services in Israel. Included in the study were subjects 65 years of age and above with new-onset DM. The primary outcome measures were all-cause mortality and coronary revascularization procedures with either percutaneous coronary intervention or coronary artery bypass grafting.

Results: Participants (n = 2,994) were stratified into four groups according to their mean HbA1c levels during the follow-up period (<6.5% [48 mmol/mol], 6.5-6.99% [48-52 mmol/mol], 7-7.49% [53-57 mmol/mol], and ≥7.5% [58 mmol/mol]). During a mean follow-up of 5.54 ± 2.1 years, 1,173 (39.17%) participants died and 285 (9.51%) underwent coronary revascularization. An HbA1c level >7.5% (58 mmol/mol) was associated with a significantly increased all-cause mortality rate (hazard ratio [HR] 1.74 [95% CI 1.2-1.8], P < 0.0001). This difference remained statistically significant after a multivariate model adjusted for the conventional cardiovascular risk factors and for the use of hypoglycemic agents and statins. Kaplan-Meier survival plots revealed lower survival rates in this group of patients. Coronary revascularization rates were highest among subjects with HbA1c 6.5-6.99% (48-52 mmol/mol) (HR 1.6 [1.01-2.4], P < 0.05) and lowest in patients with HbA1c ≥7.5% (58 mmol/mol).

Conclusions: An HbA1c level >7.5% (58 mmol/mol) is associated with increased risk for all-cause mortality and with a lower revascularization rate in elderly patients with new-onset DM.

Figure 1

Kaplan-Meier survival plots for all-cause mortality according to HbA_1c levels.