Glycemic control and cardiovascular disease in 7,454 patients with type 1 diabetes: an observational study from the Swedish National Diabetes Register (NDR).
OBJECTIVE
We assessed the association between A1C and cardiovascular diseases (CVDs) in an observational study of patients with type 1 diabetes followed for 5 years.


METHODS
A total of 7,454 patients were studied from the Swedish National Diabetes Register (aged 20-65 years, diabetes duration 1-35 years, followed from 2002 to 2007).


RESULTS
Hazard ratios (HRs) for fatal/nonfatal coronary heart disease (CHD) per 1% unit increase in baseline or updated mean A1C at Cox regression analysis were 1.31 and 1.34 and 1.26 and 1.32, respectively, for fatal/nonfatal CVD (all P < 0.001 after adjustment for age, sex, diabetes duration, blood pressure, total and LDL cholesterol, triglycerides, BMI, smoking, and history of CVD). HRs were only slightly lower for CHD (P = 0.002) and CVD (P = 0.002-0.007) after also adjusting for albuminuria. Adjusted 5-year event rates of CHD and CVD increased progressively with higher A1C, ranging from 5 to 12%, as well as when subgrouped by shorter (1-20 years) or longer (21-35 years) duration of diabetes. A group of 4,186 patients with A1C 5-7.9% (mean 7.2) at baseline showed risk reductions of 41% (95% confidence intervals: 15-60) (P = 0.005) for fatal/nonfatal CHD and 37% (12-55) (P = 0.008) for CVD, compared with 3,268 patients with A1C 8-11.9% (mean 9.0), fully adjusted also for albuminuria.


CONCLUSIONS
This observational study of patients in modern everyday clinical practice demonstrates progressively increasing risks for CHD and CVD with higher A1C, independently of traditional risk factors, with no J-shaped risk curves. A baseline mean A1C of 7.2% showed considerably reduced risks of CHD and CVD compared with A1C 9.0%, emphasizing A1C as a strong independent risk factor in type 1 diabetes.
Eeg-Olofsson
Katarina
K
Institute of Medicine, Sahlgrenska University Hospital, University of Gothenburg, Göteborg, Sweden. katarina.eeg-olofsson@vgregion.se
Cederholm
Jan
J
Nilsson
Peter M
PM
Zethelius
Björn
B
Svensson
Ann-Marie
AM
Gudbjörnsdóttir
Soffia
S
Eliasson
Björn
B
D000328:Adult; D000368:Aged; D000419:Albuminuria / Q000401:mortality; D003324:Coronary Artery Disease / Q000401:mortality*; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000188:drug therapy / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012042:Registries / Q000706:statistics & numerical data*; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human