title: Change in HbA1c over 3 years does not improve the prediction of cardiovascular disease over and above HbA1c measured at a single time point.
abstract: OBJECTIVE
  HbA1c is an important risk factor for cardiovascular disease (CVD), with 1% higher HbA1c levels associated with a 10-20% increased risk of CVD. Little is known about the association between change in HbA1c over time and cardiovascular risk in non-diabetic populations. This study examined the association between change in HbA1c over time and cardiovascular risk in a non-diabetic British population.
  
  
  METHODS
  We used data on HbA1c collected at baseline and at a second health examination 3 years later among a population of 5,790 non-diabetic men and women who participated in the European Prospective Investigation of Cancer (EPIC)-Norfolk. The association between change in HbA1c over 3 years and incident cardiovascular events over the following 8 years was examined using multivariate Cox regression. We also examined whether information on change in HbA1c over time improved prediction of cardiovascular events over a single measure of HbA1c by comparing the area under the receiver operating characteristic curves (aROC) and computing the net reclassification improvement.
  
  
  RESULTS
  The mean change (SD) in HbA1c over 3 years was 0.13% (0.52). During 44,596 person-years of follow-up, 529 cardiovascular events occurred (incidence 11.9 per 1,000 person-years). Each 0.5% rise in HbA1c over 3 years was associated with a 9% increase in risk of a cardiovascular event (HR 1.09; 95% CI 1.01, 1.18) after adjustment for baseline HbA1c and other major cardiovascular risk factors. However, change in HbA1c was not associated with cardiovascular risk after adjustment for HbA1c at follow-up. Multivariate models with and without information on change in HbA1c over time showed a similar aROC of 0.78. Adding change in HbA1c to the model with HbA1c at follow-up did not improve risk classification.
  
  
  CONCLUSIONS
  Addition of information on change in HbA1c over 3 years did not improve the prediction of CVD over and above information on HbA1c and other major cardiovascular risk factors from a single time point.
authors: MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK. parinya.chamnan@mrc-epid.cam.ac.uk
authors: P
authors: P
authors: Chamnan
authors: R K
authors: RK
authors: Simmons
authors: K T
authors: KT
authors: Khaw
authors: N J
authors: NJ
authors: Wareham
authors: S J
authors: SJ
authors: Griffin
mesh_terms: D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000209:etiology*; D015331:Cohort Studies; D016002:Discriminant Analysis; D004739:England / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000503:physiopathology*; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012372:ROC Curve; D012307:Risk Factors
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
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