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The Cardiovascular Autonomic Neuropathy (CAN) Subcommittee of the Toronto Consensus Panel on Diabetic Neuropathy worked to update CAN guidelines, with regard to epidemiology, clinical impact, diagnosis, usefulness of CAN testing, and management. CAN is the impairment of cardiovascular autonomic control in the setting of diabetes after exclusion of other causes. The prevalence of confirmed CAN is around 20%, and increases up to 65% with age and diabetes duration. Established risk factors for CAN are glycaemic control in type 1 and a combination of hypertension, dyslipidaemia, obesity, and glycaemic control in type 2 diabetes. CAN is a risk marker of mortality and cardiovascular morbidity, and possibly a progression promoter of diabetic nephropathy. Criteria for CAN diagnosis and staging are: (1) one abnormal cardiovagal test result identifies possible or early CAN; (2) at least two abnormal cardiovagal test results are required for definite or confirmed CAN; and (3) the presence of orthostatic hypotension in addition to abnormal heart rate test results identifies severe or advanced CAN. Progressive stages of CAN are associated with increasingly worse prognosis. CAN assessment is relevant in clinical practice for (1) diagnosis of CAN clinical forms, (2) detection and tailored treatment of CAN clinical correlates (e.g. tachycardia, orthostatic hypotension, non-dipping, QT interval prolongation), (3) risk stratification for diabetic complications and cardiovascular morbidity and mortality, and (4) modulation of targets of diabetes therapy. Evidence on the cost-effectiveness of CAN testing is lacking. Apart from the preventive role of intensive glycaemic control in type 1 diabetes, recommendations cannot be made for most therapeutic approaches to CAN.

Design ACCORD is a parallel group, randomized trial designed to investigate whether intensive glycemic therapy with a target HbA1c of <6.0% versus standard therapy with a target of 7.0 to 7.9% reduces cardiovascular disease (CVD) morbidity, mortality, and microvascular complications in participants with type 2 diabetes. Methods Volunteers with established type 2 diabetes, HbA1c levels ≥ 7.5% and CVD or two or more CVD risk factors were recruited at 77 clinical sites across the U.S. and Canada. Instructional materials, behavioral counseling, glucose-lowering medications and self-monitoring supplies were provided by the study. Therapeutic regimens were individualized on the basis of randomized assignment and response to therapy. This investigation examines the effect of treatment to glycemic goals on occurrence of microvascular diabetes complications. Prespecified composite outcomes were: 1) dialysis or renal transplantation, or serum creatinine >291.7 micromol/L, or retinal photocoagulation or vitrectomy, and 2) these plus peripheral neuropathy. Thirteen prespecified secondary measures of kidney, eye, and peripheral nerve function were also evaluated. Randomization was performed at clinical sites using a central randomization routine available on the study website. Both investigators and participants were unmasked to treatment arm assignment. Results A total of 10,251 participants were randomized (5,128 intensive and 5,123 standard) between January, 2001 and October, 2005. This analysis includes 10,234 patients (5,107 intensive and 5,108 standard). Intensive therapy was stopped before study end due to increased mortality, and patients were transitioned to standard therapy. Outcomes are reported at transition and at study end. At transition, the first composite outcome occurred in 443/5107 and 444/5108 participants in the intensive and standard arms, respectively (p= 0.99), and the second outcome in 1591/5107 and 1659/5108 participants in intensive and standard arms (p=0.20). Results were similar at study end. Secondary measures at study end favoring intensive therapy (p<0.05) included development of macroalbuminuria, cataract extraction, visual acuity, a score of >2.0 on the Michigan Neuropathy Screening Instrument, loss of ankle jerk and light touch. Conclusions Intensive glycemic treatment did not reduce the risk of advanced measures of microvascular outcomes, but delayed the onset of macroalbuminuria and some measures of eye complications and neuropathy. These benefits must be weighed against the increase in total and CVD-related mortality, increased weight gain, and higher risk for severe hypoglycemia.

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Role of the Funder/Sponsor: Drs Linder (NIH), Imperatore, and Saydah (CDC) were participating members of the study steering committee and the writing group for this manuscript because of the cooperative funding agreements. They were involved in the design of the study but not the conduct of the study; they were not involved in the collection, management, and analysis of the data, but were involved in interpretation of the data; they were involved in the preparation, review, and approval of the manuscript and the decision to submit the manuscript for publication.