Non-Dipping Heart Rate and Microalbuminuria in Type 2 Diabetes Mellitus

OBJECTIVES: The aim of this study was to identify factors which are independently associated with non-dipping heart rate (HR) in a type 2 diabetic population at high risk of cardiovascular disease. METHODS: The study recruited 179 type 2 diabetic subjects with a mean diabetes duration of 18.3 years and with proliferative retinopathy. All underwent 24-hour blood pressure and HR monitoring, and were assessed for markers of inflammation, insulin resistance, albuminuria, presence of peripheral neuropathy and peripheral vascular disease. Subjects whose night-time HR did not decrease by more than 10% as compared to daytime readings were classified as non-dippers. RESULTS: Univariate analysis revealed that non-dippers had significantly higher logarithmic albumin-creatinine ratio (ACR; p = 0.001) and higher platelet count (p = 0.014). Also, non-dippers were more likely to be on β-blockers (p = 0.037). Binary logistic regression analysis showed that logarithmic ACR (p = 0.001) and platelet count (p = 0.026) were independent predictors of non-dipping HR, even when correcting for β-blocker use. CONCLUSIONS: In this high-risk type 2 diabetic population, non-dipping HR was independently associated with ACR and platelet count, suggesting that non-dipping HR might give an indication of underlying generalised atherosclerosis in diabetic patients. Also, non-dipping HR may represent a novel mechanism explaining the association of nephropathy with cardiovascular events. This merits further study.