Prevalence and comorbidities of double diabetes.

Background: A growing number of people with type 1 diabetes (T1DM) are identified with features of metabolic syndrome (MS) known as "double diabetes", but epidemiologic data on the prevalence of MS in T1DM and its comorbidities are still lacking. Aim of this cross sectional study is to better estimate the prevalence of MS in T1DM, and to assess its association with comorbidities.

Methods: Data of 31,119 persons with autoimmune diabetes mellitus were analysed for signs of MS and presence of late complications. Double diabetes was defined as T1DM coexisting with MS (obesity, hypertension, dyslipidemia). Multiple linear or logistic regression analyses were performed to identify associations between double diabetes and late complications.

Results: 25.5% (n=7926) of persons with T1DM presented additionally the MS. Persons with double diabetes showed significantly more macrovascular comorbidities (coronary heart disease 8.0% versus 3.0% w/o MS, stroke 3.6% versus 1.6%, diabetic foot syndrome 5.5% versus 2.1%). Also microvascular diseases were increased in people with double diabetes (retinopathy 32.4% versus 21.7%, nephropathy 28.3% versus 17.8%). Both macrovascular and microvascular comorbidities were increased independent of glucose control, even if patients with good metabolic control (HbA1c <7.0%, 53mmol/mol) showed significantly less macrovascular (coronary heart disease 2.3% versus 1.8%, p<0.0001) and microvascular problems (retinopathy 8.7% versus 6.6%, p<0.0001).

Conclusions: Double diabetes seems to be an independent and important risk factor for persons with T1DM in developing macrovascular and microvascular comorbidities. Therefore, patients should be identified and development of MS should be avoided. Longterm studies are needed to observe the effect of insulin resistance on patients with autoimmune diabetes.