Hypertension: Incidence, Causes, Diagnosis, Treatment
What is Hypertension?
Hypertension (high blood pressure) is an important risk factor for the future development of cardiovascular disease. It can be defined as a condition where blood pressure is elevated to an extent that clinical benefit is obtained from blood pressure lowering. Blood pressure measurement includes systolic and diastolic components, and both are important in determining an individual’s cardiovascular risk.
Incidence Rate of Hypertension
Between 10% and 25% of the population are expected to benefit from drug treatment of hypertension; the exact figure depending on the cut-off value for blood pressure and the age group considered for active treatment. In 90–95% of cases of hypertension, there is no underlying medical illness to cause high blood pressure.
Causes of Hypertension
Primary Hypertension (90–95%)
- Essential Hypertension
Secondary Hypertension (5–10%)
- Renal diseases
- Endocrine diseases
- Steroid excess: hyperaldosteronism (Conn’s syndrome); hypercorticoidism (Cushing’s syndrome)
- Growth hormone excess: acromegaly
- Catecholamine excess: phaeochromocytoma
- Others: pre-eclampsia
- Vascular causes – Renal artery stenosis: fibromuscular hyperplasia; renal artery atheroma; coarctation of the aorta
When To Consult A Doctor
Hypertension is often an incidental finding when subjects present for screening or with unrelated conditions. Severe cases may present with headache, visual disturbances or evidence of target organ damage (stroke, ischaemic heart disease or renal failure). In the UK, all patients under 80 years of age should have their blood pressure checked at least every 5 years, with an annual review for those with high normal values in the range 135–139 mmHg systolic or 85–89 mmHg diastolic.
Diagnosis of Hypertension
In the UK, it is recommended that all adults have their blood pressure measured every 5 years. Those with high normal (130–139 mmHg systolic or 85–89 mmHg diastolic) or previous high readings should have annual measurement. Blood pressure should be measured using a well-maintained sphygmomanometer of validated accuracy. Blood pressure should initially be measured in both arms and the arm with the highest value used for subsequent readings.
Treatment for Hypertension
Non-pharmacological management of hypertension is important, although the effects are often disappointing.
- Patients with mild hypertension in the range 140–159/90–100 mmHg can be assessed for levels of risk while offered lifestyle advice. General health education is important to allow patients to make informed choices about management.
- In order to maximise potential benefit, patients should receive clear and unambiguous advice, including written information they can digest in their own time.
- In patients who are overweight, weight loss results in reduction in blood pressure of about 2.5/1.5mmHg/kg. The DASH diet (Dietary Approaches to Stop Hypertension) was evaluated in a clinical trial and found to lower blood pressure significantly (4.5/2.7mmHg) compared with a typical US diet. This diet emphasises fruit, vegetables, and low-fat dairy produce in addition to fish, low-fat poultry and whole grains while minimising red meat, confectionary and sweetened drinks.
- Subjects should reduce their salt intake, for example, by not adding salt to food on the plate. A daily sodium intake of <100 mmol (i.e. 6 g sodium chloride or 2.4g elemental sodium) should be the aim.
- There is a significant amount of hidden salt in processed meat, ready meals, cheese and even bread.
A dietary assessment may be required to accurately quantify a patient’s salt intake and advise on how reductions might be made.
- Most subjects will need to control their intake of calories and saturated fat.
- Regular aerobic exercise, at a level appropriate to the individual subject, at least 3 times a week for at least 30 min derives maximum benefit.
- This results in improved physical fitness as well as a reduction in blood pressure.
- Alcohol intake should be restricted to two (females) or three (males) units per day.
- As smoking does not affect blood pressure, it increases cardiovascular risk and patients should quit or, if this is not possible, reduce their cigarette consumption.
- Unless hypertension is severe, it is appropriate to observe the subject over several months while instituting nonpharmacological interventions. However, if there is a more urgent need for drug treatment, non-pharmacological interventions should occur in parallel.
Drug Treatment for Hypertension
- Lifestyle advice should be provided to all patients with any degree of hypertension.
- Patients with severe hypertension (>220/120 mmHg confirmed on several readings on the same occasion) should be treated immediately and some guidance suggests that dual therapy should be commenced immediately in patients with blood pressure >20 mmHg above their target as monotherapy is unlikely to be fully effective .
- Patients with blood pressures in the range 160– 220/100–120 mmHg should be monitored over several weeks and treated if blood pressure remains in this range. The period of observation before starting treatment depends on the severity of the hypertension and the presence or absence of end-organ damage .
- Patients whose blood pressure is in the range 140–159/90–99 mmHg should be observed annually unless they have evidence of target organ damage, cardiovascular complications, diabetes or a calculated cardiovascular risk >20% over 10 years, in which case drug treatment should be offered.
- Patients with blood pressure in the range 135–139/85–89 mmHg should be reassessed annually, while those with blood pressure lower than this can be rechecked every 5 years.