Abstract
Diabetic retinopathy has been associated with cardiac autonomic dysfunction in both type 1 and type 2 diabetes mellitus (DM) patients. Heart rate (HR) changes during exercise testing indicate early alterations in autonomous tonus. The aim of the present study was to investigate the association of diabetic retinopathy with exercise-related HR changes. A cross-sectional study was performed on 72 type 2 and 40 type 1 DM patients. Autonomic dysfunction was assessed by exercise-related HR changes (Bruce protocol). The maximum HR increase, defined as the difference between the peak exercise rate and the resting rate at baseline, and HR recovery, defined as the reduction in HR from the peak exercise to the HR at 1, 2, and 4 min after the cessation of the exercise, were determined. In type 2 DM patients, lower maximum HR increase (OR = 1.62, 95%CI = 1.03-2.54; P = 0.036), lower HR recovery at 2 (OR = 2.04, 95%CI = 1.16-3.57; P = 0.012) and 4 min (OR = 2.67, 95%CI = 1.37-5.20; P = 0.004) were associated with diabetic retinopathy, adjusted for confounding factors. In type 1 DM, the absence of an increase in HR at intervals of 10 bpm each during exercise added 100% to the odds for diabetic retinopathy (OR = 2.01, 95%CI = 1.1-3.69; P = 0.02) when adjusted for DM duration, A1c test and diastolic blood pressure. In conclusion, early autonomic dysfunction was associated with diabetic retinopathy. The recognition of HR changes during exercise can be used to identify a high-risk group for diabetic retinopathy.
Highlights
Hypertension is a well-known risk factor for diabetic retinopathy [1]
blood pressure (BP) levels, glycemic control, diabetes mellitus (DM) duration, lipid profile, Urinary albumin excretion rate (UAER), body mass index, waist circumference, and smoking habit did not differ between groups
Data are reported as means ± SD or number (%) except for triglycerides and urinary albumin excretion rate, which are reported as median. *P < 0.05 compared to absence of retinopathy (Student t-test for continuous variable; chi-square test for categorical variables)
Summary
Even minor blood pressure (BP) increases during ambulatory BP monitoring might influence the development of diabetic retinopathy [2], probably due to decreased vasomotor control of the circulation of the retinal vessels allowing even small alterations in BP to impact the retina. Diabetic retinopathy has been associated with cardiac autonomic dysfunction in both type 1 [3] and type 2 diabetes mellitus (DM) patients [4]. Heart rate (HR) changes related to exercise testing [5,6] may detect early alterations in autonomous tonus and are a major predictor of sudden death and cardiac mortality in healthy and postmyocardial infarct patients [7-9]. The aim of the present study was to investigate the association of diabetic retinopathy with a specific HR profile related to exercise testing in DM patients in the absence of both ischemic heart disease and clinical autonomic neuropathy.
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