Risk of cardiovascular disease and total mortality in adults with type 1 diabetes: Scottish registry linkage study

Abstract

Background: Randomized controlled trials have shown the importance of tight glucose control in type 1 diabetes (T1DM), but few recent studies have evaluated the risk of cardiovascular disease (CVD) and all-cause mortality among adults with T1DM. We evaluated these risks in adults with T1DM compared with the non-diabetic population in a nationwide study from Scotland and examined control of CVD risk factors in those with T1DM.

Methods and findings: The Scottish Care Information-Diabetes Collaboration database was used to identify all people registered with T1DM and aged ≥20 years in 2005-2007 and to provide risk factor data. Major CVD events and deaths were obtained from the national hospital admissions database and death register. The age-adjusted incidence rate ratio (IRR) for CVD and mortality in T1DM (n = 21,789) versus the non-diabetic population (3.96 million) was estimated using Poisson regression. The age-adjusted IRR for first CVD event associated with T1DM versus the non-diabetic population was higher in women (3.0: 95% CI 2.4-3.8, p<0.001) than men (2.3: 2.0-2.7, p<0.001) while the IRR for all-cause mortality associated with T1DM was comparable at 2.6 (2.2-3.0, p<0.001) in men and 2.7 (2.2-3.4, p<0.001) in women. Between 2005-2007, among individuals with T1DM, 34 of 123 deaths among 10,173 who were <40 years and 37 of 907 deaths among 12,739 who were ≥40 years had an underlying cause of death of coma or diabetic ketoacidosis. Among individuals 60-69 years, approximately three extra deaths per 100 per year occurred among men with T1DM (28.51/1,000 person years at risk), and two per 100 per year for women (17.99/1,000 person years at risk). 28% of those with T1DM were current smokers, 13% achieved target HbA(1c) of <7% and 37% had very poor (≥9%) glycaemic control. Among those aged ≥40, 37% had blood pressures above even conservative targets (≥140/90 mmHg) and 39% of those ≥40 years were not on a statin. Although many of these risk factors were comparable to those previously reported in other developed countries, CVD and mortality rates may not be generalizable to other countries. Limitations included lack of information on the specific insulin therapy used.

Conclusions: Although the relative risks for CVD and total mortality associated with T1DM in this population have declined relative to earlier studies, T1DM continues to be associated with higher CVD and death rates than the non-diabetic population. Risk factor management should be improved to further reduce risk but better treatment approaches for achieving good glycaemic control are badly needed. Please see later in the article for the Editors' Summary.

Conflict of interest statement

The authors have declared the following competing interests: Sarah H. Wild has received two honoraria from Novo Nordisk, paid to her research funds in December 2010 and March 2011, for speaking at an advisory board and symposium on the topic of diabetes and cancer. Norman R. Peden has received travel grants from Pfizer Inc., Novo Nordisk, and Eli Lilly, and he holds shares in GlaxoSmithKline. John R. Petrie is the recipient of lecture honoraria, travel support and consultancy fees from pharmaceutical companies manufacturing thiazolodinediones (Takeda & GlaxoSmithKline), as well as from companies manufacturing other diabetes products (Novo Nordisk, Sanofi-Aventis). Recipient of support in kind from Merck-Serono for a charity-funded investigator-led study (REMOVAL NCT01483560). Helen M. Colhoun has served on clinical trial advisory panels for Sanofi-Aventis, Pfizer Inc., Novartis Pharmaceuticals, and Eli Lilly. She has also received research support from Roche Pharmaceuticals, Pfizer Inc., Eli Lilly, Boehringer Ingelheim, and Astra Zeneca as part of an EU Innovative Medicines Initiative research grant. None of these activities directly relate to this manuscript. Shona J. Livingstone, Helen C. Looker, Eleanor J. Hothersall, Robert S. Lindsay, John Chalmers, Stephen Cleland, Graham P. Leese, John McKnight, Andrew D. Morris, Donald W. M. Pearson, Sam Philip, Naveed Sattar, and Frank Sullivan have no conflicts of interest to declare.

Figures

Figure 1. Age-standardised rates for primary CVD, primary CHD, primary cerebrovascular disease, and all-cause mortality by sex and age band for people with type 1 diabetes or non-diabetic in Scotland 2005–2007.

All lines are interpolations. y axis for mortality panel has a different range to the other panels for purposes of display.

Figure 2. Most common underlying causes of death in type 1 diabetes, 2005–2007.

Figure 3. Risk factor prevalence in type 1 diabetes, May 2008.