Hypertension is the leading risk factor for cardiovascular disease and contributes to 7.6 million premature deaths every year (WHO, 2013). Lifestyle counselling is recommended as a first line therapy for reducing blood pressure (BP) and risk for cardiovascular events. Meta-analytic reviews have demonstrated that lifestyle counselling of exercise and diet can reduce systolic BP up to 3-9 mmHg relative to controls. However, a major challenge for a community-based preventive strategy is to extend the reach of therapeutic lifestyle counselling to individuals with hypertension who may have limited access to these services. With the advancement in Internet technology and improved access to the Internet, there is emerging evidence that Internet-based lifestyle interventions may be well-suited to meet this challenge.
Classification and Prevalence of Hypertension
Resting BP is organized into various categories in order to help identify those individuals at risk from high BP and to facilitate therapeutic treatments. The optimal resting BP recommended by the Canadian Hypertension Education Program and the United States Joint National Committee for Detection, Evaluation and Treatment of High BP is a systolic BP of less than 120 mmHg and a diastolic BP of less than 80 mmHg. Hypertension is diagnosed when high systolic (≥140 mmHg) or diastolic BP (≥90mmHg) are recorded at two or more visits to the medical doctor. Hypertension is further separated into stages. Stage 1 and 2 (80-85%) is the most common form of hypertension.
|Category||Systolic BP (mmHg)||Diastolic BP (mmHg)|
Hypertension is a major health concern globally. The World Health Organization rates hypertension as one of the leading causes of premature death worldwide (WHO, 2013). In the developed world, about 330 million people have hypertension, as do around 640 million in the developing world. It is estimated there will be 1.56 billion adults living with hypertension by 2025. Therefore, it is imperative to develop innovative population-based BP control strategies.
Risk of Hypertension
Epidemiological studies have repeatedly identified independent risk relation between hypertension and various disorders such as stroke, heart failure, coronary artery disease and renal disease. Hypertension is a risk factor for all clinical manifestations of atherosclerosis. This section will describe the major organ complications associated with hypertension which involves the heart, brain and kidneys.
Hypertension can result in structural and functional changes in the heart leading to left ventricular hypertrophy. As a response to pressure overload, left ventricular mass can undergo concentric (increase in wall thickness) and eccentric (increase in chamber size) hypertrophy and leading to chronic heart failure. Increased left ventricular mass was associated with death from all causes: relative risk, 1.49 [95% confidence interval (CI), 1.14 to 1.94] in men and 2.01 [95%CI, 1.44 to 2.81] in women. Furthermore, hypertension can contribute to atherosclerotic coronary artery disease, which can result in abnormalities of blood flow and may lead to myocardial infarction. Recent clinical trials have reported that control of systolic BP (target of <130mmHg versus <140 mmHg) can regress left ventricular hypertrophy and reduce the risk of cardiovascular disease. These research studies demonstrated the importance of BP control.
Hypertension is the leading risk factor for stroke and increases the risk for cognitive impairment and dementia. Stroke is a generic term to describe a clinical syndrome that includes focal ischemia, brain hemorrhage and subarachnoid hemorrhage. The increased intraluminal pressure from hypertension can lead to alteration in endothelium and smooth muscle function in the intracerebral arteries. The endothelial damage can lead to local thrombi formation which can result in occlusion of the blood vessel. Degenerative changes in smooth muscle cells and endothelium can increase the chance for intra-cerebral hemorrhages.
Epidemiological studies have shown that patients with hypertension have a 3-fold greater risk of stroke than individuals with normal BP. In the Framingham study, 56% of stroke incidence in men and 66% in women were attributed directly to hypertension. Reduction of BP by 5-6 mmHg is likely to induce a 4-45% decrease in stroke risk in middle-aged and older individuals.
Hypertension is the second leading cause of chronic kidney failure in North America. High BP can damage blood vessels in the kidney, which can affect glomerular filtration rate. The decreased rate of removing waste and extra fluids from the body can then elevate BP, creating a dangerous positive feedback cycle. Reduced glomerular filtration rate (30 ml/min per 1.73 m2) is associated with an increased cardiovascular disease risk of 22%. BP control is critical in preventing chronic kidney disease and cardiovascular disease.