Hypertension is a chronic condition  of concern due to its role in the causation of coronary heart disease, stroke and other vascular complications.It is one of the major risk factors for cardiovascular mortality,which accounts for 20_ 50 per cent of all deaths. 

The blood pressure is the single most useful test for identifying individuals at a high risk of developing  CHD. Hypertension accelerates the atherosclerotic process,especially if hyperlipidemia is also present and contributes importantly to CHD.

For classification, intervention trials included only adults aged 18 years or older.Definition and classification of hypertension refer to adults not taking anti_ hypertensive drugs and not actually  ill, and based on the average of two or more readings on two or more occasions after initial  screening.The  classification of hypertension by blood pressure level.

When systolic  and diastolic blood pressure fall into different categories, the higher category should be selected to classify the individual's blood pressure." Isolated systolic hypertension " is defined as a systolic  blood pressure of 140 mm of Hg or more  and a diastolic blood pressure of less than 90 mm of Hg.


 Hypertension is divided into primary  (essential) and secondary .Hypertension is classified as " essential " when the causes are generally  unknown . Essential  hypertension is the most prevalent  form of hypertension accounting for 90 per cent of all cases of hypertension. Hypertension is classified as " secondary " when some other disease process or abnormality is involved  in its causation. Prominent  among these are diseases of kidney (chronic glomerulo_ nephritis and chronic pyelonephritis), tumours of the adrenal glands, congenital narrowing   of the aorta and toxemia of pregnancy. Altogether, these are estimated to account for about 10  per cent or less of the cases of hypertension. 

Risk factors for hypertension:

Hypertension is not only one of the major risk factors for most forms of cardiovascular disease, but that it is a condition with its own risk  factors. There may be classified  as:

1. Non_ modifiable risk  factors:

(a) AGE: Blood pressure rises with age  in both sexes and the rise is greater in those with higher initial blood pressure. Age probably represents an accumulation of environmental influences and the effects of genetically programmed senescence in body systems. 

(b) SEX: Early in life there is little evidence of a difference in blood pressure between the sexes. However, at adolescence  men display a higher average level.

(c) GENETIC FACTORS: There is considerable evidence  that blood pressure levels are determined in part by genetic  factors, and that the inheritance is  polygenic. 

 Family studies have shown that the  children of two normotensive parents have 3 per cent possibility of developing hypertension,  whereas this possibility is 45 per cent in children of two hypertensive parents. Blood pressure levels among first degree adult relatives have also been noted to be statistically  significant. 

(d) ETHNICITY: Population  studies have consistently revealed  higher blood pressure levels in black communities than other ethnic groups.

2. Modifiable risk factors:

(a) OBESITY : Epidemiological observations have identified  obesity as a risk factor for hypertension. The greater the weight gain, the greater the risk of high blood pressure .Data also indicate that when people with high blood pressure lose weight, their blood pressure generally decreases. " Central obesity " indicated by an increased waist to hip ratio, has been positively  correlated with high blood pressure in several populations. 

(b) SALT INTAKE : There is an increasing body of evidence to the effect that a high salt intake (i.e., 7_ 8 g per day) increases blood pressure proportionately. Low sodium intake has been found to lower the blood pressure.

 Besides sodium,  there are other mineral elements such as potassium which are determinants of blood  pressure. Potassium antagonizes the biological effects of sodium, and thereby reduces blood pressure. 

(c) SATURATED FAT: The evidence suggest that saturated fat raises blood pressure as well as serum cholesterol. 

(d) DIETARY FIBRE: Several  studies indicate that the risk of CHD and hypertension is inversely related  to the consumption of dietary fibre. Most fibres reduce plasma total and LDL  cholesterol. 

(e) ALCOHOL : High alcohol  intake is associated with an increased  risk of high blood pressure. It appears that alcohol  consumption raises systolic pressure more that the diastolic. But the finding that blood pressure returns to normal with abstinence suggests that alcohol _ induced elevations may not be fixed, and do not necessarily lead to sustained  blood pressure elevation.

(f) HEART RATE : When  groups of normotensive and untreated hypertensive subjects, matched for age and sex, are compared, the heart rate of the hypertensive group is invariably higher.This may reflect a resetting of  sympathetic activity  at a higher level.

(g) PHYSICAL ACTIVITY: Physical  activity by reducing body weight may have an indirect effect on blood pressure. 

(h) ENVIRONMENTAL STRESS: The term hypertension itself implies  a disorder initiation by tension or  stress. It is an accepted fact that psychosocial factors operate through mental processes, consciously or unconsciously, to produce hypertension. 

(i) SOCIO_ ECONOMIC STATUS: In developed countries consistently higher levels of blood pressure have been noted in lower socio_ economic  groups. This inverse relation has been noted with levels of education,  income and occupation. However,  in societies that are transitional or pre_ transitional, a higher prevalence of hypertension have been noted in upper socio_ economic groups. This probably represents the initial stage of the epidemic of CVD.

(j) OTHER FACTORS : The commonest  present cause of secondary hypertension is oral contraception, because of the estrogen component in combined preparations. Other factors such as noise,vibration,temperature and humidity require further investigation. 

Prevention of Hypertension:

The low prevalence of hypertension in some communities indicates that hypertension is potentially preventable. The WHo  has recommended the following approaches in the prevention of hypertension:

1. Primary  prevention 

(a) Population strategy 

(b) High _ risk strategy 

2. Secondary prevention 

1. Primary  prevention:

Although  control of hypertension  can be successfully  achieved by medication (secondary prevention) the ultimate goal in general is primary prevention. Primary prevention has been defined as " all measures to reduce the incidence of disease in a population by reducing  the risk of onset". The earlier the prevention starts the more likely it is to be effective. 

    The population  approach is directed at the whole population,  irrespective of individual risk levels.  The concept of population approach is based on the fact that even a small reduction in the average  blood  pressure of a population would produce  a large reduction in the incidence of cardiovascular complications such as stroke and CHD. The goal of the population approach is to shift the community distribution of  blood pressure towards lower levels or " biological  normality ".This involves a multifactorial approach, based on the following non_ pharmacotherapeutic interventions: 

(a)  NUTRITION: Dietary changes are  of paramount importance. These comprise :

(i)  Reduction  of salt intake to an average of not more than 5 g per day 

(ii)  Moderate  fat intake 

(iii) The avoidance of a high alcohol intake, and

(iv) Restriction of energy  intake appropriate to body needs.

(b)   WEIGHT REDUCTION: The prevention and correction of over weight/ obesity  (Body Mass Index  greater than 25 ) is a  prudent  way of reducing the risk of hypertension and indirectly  CHD; it goes with dietary changes. 

(c) EXERCISE PROMOTION: The evidence  that regular physical activity leads to a fall in body weight,  blood lipids and blood pressure goes to suggest that regular physical activity should be encouraged as part of the strategy  for risk_ factor control.

(d) BEHAVIOURAL CHANGES: Reduction of stress and smoking , modification of personal life _ style, yoga and transcendental  meditation could be profitable. 

(e) HEALTH EDUCATION: The general  public require preventive advice on all risk factors and related health behaviour.  The whole community must be mobilized and  made aware of the possibility of primary prevention, and 

(f) SELF_ CARE: An important element in community _ based health  programmes is patient participation. The patient is taught  self_ care, i.e., to take his own blood pressure  and keep a long_ book of his readings.

        This  is also part of primary  prevention.
The aim of this approach  is " to prevent  the attainment  of levels  of blood pressure at which the institution of treatment  would be considered ". Detection  by the optimum  use of clinical  methods. Since hypertension tends to cluster in families,  the family history of hypertension and " tracking " of blood pressure from childhood may be used to identify individuals at risk.

2. Secondary prevention:

 The goal of secondary prevention is to detect and control high blood pressure in affected  individuals. Modern anti_ hypertensive  drug therapy can effectively  reduce high blood pressure and consequently,  the excess risk of morbidity and mortality from coronary,  cerebrovascular and kidney disease.  The control measures  comprise: 

(i) EARLY CASE DETECTION :  Early detection  is a major problem. This is because nhigh blood pressure rarely causes symptoms until organic damage has already occurred, and our aim should be to control it before  this happens. The only effective  method of diagnosis of hypertension is to screen the population. But screening , that is not linked to follow_ up and sustained care, is a fruitless exercise. 

   However,  when people come in contact with the health service, and if blood pressure is measured at each such contact, the bulk of the problem of detecting those in need of intervention is solved.

(ii)   TREATMENT:  In  essential  hypertension,  as in diabetes,  we cannot treat  the cause, because we do not know what it is. Instead, we try to scale down the high blood pressure should  be to  obtain a blood pressure below 140/ 90, and ideally a blood pressure of 120/ 80.Control of hypertension has been shown to reduce the incidence of stroke and other complications. This is a major reason for identifying and treating  asymptomatic hypertension. Care of hypertensives should as smoking and elevated  blood cholesterol levels. 

(iii) PATIENT COMPLIANCE: The treatment  of  high blood pressure must normally  be life_ long  and this presents problems of patients compliance, which is defined  as " the extent to which patient behaviour  ( in terms of taking medicines,  following  diets or executing other life_ style changes) coincides with clinical  prescription ".The compliance rates can be improved through education directed to patients, families  and the community. 


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