title: Association of HbA1c levels with vascular complications and death in patients with type 2 diabetes: evidence of glycaemic thresholds.
abstract: OBJECTIVE
  There is conflicting evidence regarding appropriate glycaemic targets for patients with type 2 diabetes. Here, we investigate the relationship between HbA(1c) and the risks of vascular complications and death in such patients.
  
  
  METHODS
  Eleven thousand one hundred and forty patients were randomised to intensive or standard glucose control in the Action in Diabetes and Vascular disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trial. Glycaemic exposure was assessed as the mean of HbA(1c) measurements during follow-up and prior to the first event. Adjusted risks for each HbA(1c) decile were estimated using Cox models. Possible differences in the association between HbA(1c) and risks at different levels of HbA(1c) were explored using linear spline models.
  
  
  RESULTS
  There was a non-linear relationship between mean HbA(1c) during follow-up and the risks of macrovascular events, microvascular events and death. Within the range of HbA(1c) studied (5.5-10.5%), there was evidence of 'thresholds', such that below HbA(1c) levels of 7.0% for macrovascular events and death, and 6.5% for microvascular events, there was no significant change in risks (all p > 0.8). Above these thresholds, the risks increased significantly: every 1% higher HbA(1c) level was associated with a 38% higher risk of a macrovascular event, a 40% higher risk of a microvascular event and a 38% higher risk of death (all p < 0.0001).
  
  
  CONCLUSIONS
  In patients with type 2 diabetes, HbA(1c) levels were associated with lower risks of macrovascular events and death down to a threshold of 7.0% and microvascular events down to a threshold of 6.5%. There was no evidence of lower risks below these levels but neither was there clear evidence of harm.
authors.affiliation: The George Institute for Global Health, PO Box M201, Missenden Road, Camperdown, NSW 2050, Sydney, NSW, Australia. szoungas@georgeinstitute.org.au
authors.forename: S
authors.initials: S
authors.lastname: Zoungas
authors.forename: J
authors.initials: J
authors.lastname: Chalmers
authors.forename: T
authors.initials: T
authors.lastname: Ninomiya
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: M E
authors.initials: ME
authors.lastname: Cooper
authors.forename: S
authors.initials: S
authors.lastname: Colagiuri
authors.forename: G
authors.initials: G
authors.lastname: Fulcher
authors.forename: B E
authors.initials: BE
authors.lastname: de Galan
authors.forename: S
authors.initials: S
authors.lastname: Harrap
authors.forename: P
authors.initials: P
authors.lastname: Hamet
authors.forename: S
authors.initials: S
authors.lastname: Heller
authors.forename: S
authors.initials: S
authors.lastname: MacMahon
authors.forename: M
authors.initials: M
authors.lastname: Marre
authors.forename: N
authors.initials: N
authors.lastname: Poulter
authors.forename: F
authors.initials: F
authors.lastname: Travert
authors.forename: A
authors.initials: A
authors.lastname: Patel
authors.forename: B
authors.initials: B
authors.lastname: Neal
authors.forename: M
authors.initials: M
authors.lastname: Woodward
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001786:Blood Glucose / Q000032:analysis*; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000188:drug therapy*; D003925:Diabetic Angiopathies / Q000097:blood* / Q000401:mortality* / Q000473:pathology; D004359:Drug Therapy, Combination; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D006943:Hyperglycemia / Q000517:prevention & control*; D006973:Hypertension / Q000517:prevention & control; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D008297:Male; D055806:Microvessels / Q000187:drug effects / Q000473:pathology; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors
chemical_list: D000959:Antihypertensive Agents; D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; C517652:hemoglobin A1c protein, human