All-Cause Mortality in Patients with Type 2 Diabetes in Association with Achieved Hemoglobin A1c, Systolic Blood Pressure, and Low-Density Lipoprotein Cholesterol Levels

BACKGROUND: To identify the ranges of hemoglobin A(1c) (HbA1c), systolic blood pressure (SBP), and low-density lipoprotein cholesterol (LDL-C) levels which are associated with the lowest all-cause mortality. METHODS: A retrospective cohort of 12,643 type 2 diabetic patients (aged ≥18 years) were generated from 2002 to 2010, in Far-Eastern Memorial Hospital, New Taipei city, Taiwan. Patients were identified to include any outpatient diabetes diagnosis (ICD-9: 250), and drug prescriptions that included any oral hypoglycemic agents or insulin prescribed during the 6 months following their first outpatient visit for diabetes. HbA1c, SBP, and LDL-C levels were assessed by the mean value of all available data, from index date to death or censor date. Deaths were ascertained by matching patient records with the Taiwan National Register of Deaths. RESULTS: Our results showed general U-shaped associations, where the lowest hazard ratios occurred at HbA1c 7.0-8.0%, SBP 130-140 mmHg, and LDL-C 100-130 mg/dL. The risk of mortality gradually increases if the patient's mean HbA1c, SBP, or LDL-C during the follow-up period was higher or lower than these ranges. In comparison to the whole population, the adjusted hazard ratio (95% CI) for patients with HbA1c 7.0-8.0%, SBP 130-140 mmHg, and LDL-C 100-130 mg/dL were 0.69 (0.62-0.77), 0.80 (0.72-0.90), and 0.68 (0.61-0.75), respectively. CONCLUSIONS: In our type 2 diabetic cohort, the patients with HbA1c 7.0-8.0%, SBP 130-140 mmHg, or LDL-C 100-130 mg/dL had the lowest all-cause mortality. Additional research is needed to confirm these associations and to further investigate their detailed mechanisms.