Annals of PIMS-Editorial Board

Background: Diabetes mellitus and hypertension are a critical combination for the development of both macro and microvascular disease. Short term blood pressure (BP) variability is associated with increased cardiovascular events in both diabetic and non diabetic subjects. Diabetic patients are particularly prone to have increased BP variability and its adverse consequences.
Objective: To examine the possible difference in the short-term BP variability assessed as the standard deviation, between diabetic and non-diabetic hypertensives.
Study Design:   Cross sectional study.
Place and Duration: The study was conducted in Diabetic clinic and Cardiology outpatient department (OPD) of Sheikh Zayed Hospital, Lahore from March 2009 to July 2009.
Patients and Methods:  This study examined 60 patients, with 30 diabetic HTN (18 men and 12 women, mean age 53.5±4.2 years)and 30 non diabetic HTN (16 men and 14 women, mean age 47.8±3.2 years). Their 24 hr ambulatory BP was monitored and the short term BP variability was assessed as standard deviation from the mean 24 hr systolic and diastolic BP. The difference between two groups was measured through Independent Sample “t” test. P ≤ 0.05 was taken as significant.
Results: Diabetic HTN had a significantly greater 24-hr systolic and diastolic BP variability than nondiabetic HTN (16.83 mmHg vs. 14.60 mmHg, p < 0.04; 15.55 mmHg vs. 12.85 mmHg, p < 0.03, respectively). Interestingly it was noted that fasting blood glucose level was found to be raised in patients with increase BP variability.
Conclusion:   These results demonstrate that BP variability is increased in diabetic hypertensives.
Key Words: Dibetes mellitus. Hypertension. BP variability.

Introduction

Diabetes and hypertension are a critical combination for the development of both macro and microvascular disease. In people with type II diabetes, the prevalence of hypertension is 50% at the time of diagnosis, increasing to 80% in the presence of microalbuminuria and to more than 90% with macroalbuminuria.¹

Presently, diabetic patients are rapidly increasing in numbers, and cardiovascular complications are the most common cause of death in patients with diabetes.² Thus it would be of considerable value to identify the precise mechanism involved in the cardiovascular events associated with diabetes.

Ambulatory blood pressure monitoring has allowed an easier and more accurate determination of circadian rhythm of blood pressure under different pathophysiological conditions. Ambulatory blood pressure monitoring allows the acquisition of information not only on the average of 24 hour blood pressure, but also on the variations that characterize the blood pressure values in the course of daily life. Ambulatory blood pressure monitoring has also allowed an easier and more accurate determination of the circadian rhythm of the blood pressure under different pathological conditions, and has enabled to evaluate the effects of antihypertensive drugs.^3-4

The short term blood pressure variability is estimated as the standard deviation of beat to beat blood pressure obtained by intra arterial monitoring or the standard deviation of non - invasively monitored ambulatory blood pressure.⁵ Blood pressure variability has been shown to depend on sympathetic vascular modulation and on changes in arterial dispensability. Although the pathophysiological significance of blood pressure variability has not been elucidated in detail yet previous studies have shown that an increase in systolic blood pressure variability is associated with progression of carotid artery wall lesions and the rate of cardiovascular complications independently of increased average blood pressure values and suggested that increased systolic BP variability is an independent predictor of cardiovascular events in general population.⁶

This circadian rhythm of blood pressure in patients with diabetes has been found to have a blunted nocturnal dipping in blood pressure, which is associated with autonomic neuropathy and nephropathy.⁶

The loss of nocturnal dipping in blood pressure is considered to be the risk factor for the progression of the nephropathy itself, and to be of prognostic value with respect to target organ damage and cardiovascular morbidity in both diabetic and hypertensive patients.⁷ However, the factor involved in the blood pressure variability observed in diabetic patients are not elucidated and may themselves play an important role in the cardiovascular complications in diabetic patients.^8,9 More and better evidence on BP variability could lead to a more precise understanding of the pathogenesis of hypertension with diabetes.

The aim of this study is to examine the difference in blood pressure variability between hypertensive subjects with or without diabetes.