There has been an increase in the prevalence of diabetes mellitus over the past 40 years, both in the US and worldwide. The worldwide prevalence of diabetes in 2000 was approximately 2.8% and is estimated to grow to 4.4% by 2030. This translates to a projected rise of diabetes from 171 million in 2000 to well over 350 million in 2030. 1 The epidemic of diabetes will continue to rise as there is growing prevalence of obesity in children, which predisposes to diabetes.2 There is considerable evidence for an increased prevalence of hypertension in diabetic persons.3 In a large prospective cohort study that included 12,550 adults, the development of type 2 diabetes was almost 2.5 times as likely in persons with hypertension than in their normotensive counterparts.3,4 Similarly, evidence points to increased prevalence of hypertension in diabetic persons.3,5 Moreover, each pathophysiological disease entity serves to exacerbate the other.3,6 Both hypertension and diabetes predisposes to the development of cardiovascular disease (CVD) and renal disease.7,8 Subjects with diabetes are at about 60% increased risk of early mortality.8,9 The age-adjusted relative risk of death due to cardiovascular events in persons with type 2 diabetes is three-fold higher than in the general population. The presence of hypertension in diabetic patients substantially increases the risks of coronary heart disease, stroke, nephropathy and retinopathy.5,10,11 Indeed, when hypertension coexists with diabetes, the risk of CVD is increased by 75%, which further contributes to the overall morbidity and mortality of an already high-risk population.5,12 Generally, hypertension in type 2 diabetic persons clusters with other CVD risk factors such as microalbuminuria, central obesity, insulin resistance, dyslipidaemia, hypercoagulation, increased inflammation and left ventricular hypertrophy.5 This clustering risk factor in diabetic patients ultimately results in the development of CVD, which is the major cause of premature mortality in patients with type 2 diabetes.
Pathophysiology of Hypertension in the Diabetic Patient
Epidemiologic studies provide evidence for co-existence of hypertension and diabetes and possibly point towards a common genetic and environmental factor promoting both diabetes and hypertension. Similarly, clustering of hypertension, insulin resistance or frank type 2 diabetes, hyperlipidaemia and central obesity have been documented in several populations.13 Insulin resistance, increased tissue inflammation and reactive oxygen species (ROS) production resulting in endothelial dysfunction, increased tissue renin– angiotensin–aldosterone system (RAAS) and increased sympathetic nervous system (SNS) activity have all been implicated in this complex pathophysiology of diabetes and hypertension.