Hypertension: definition, classification, prevention

What is hypertension?

Hypertension (HTN) is defined as a mean blood pressure of 140/90 mm Hg or higher and/or current use of antihypertensive medication.

Classification of hypertension

It is classified as primary or essential hypertension and secondary hypertension.

Primary or essential hypertension

Up to 95% of people with high blood pressure have primary or essential hypertension.
The cause cannot be determined although probably results from:

  • environmental factors (among these, dietary factors have a prominent role);
  • genetic factors (the interest focused on genetic factors that influence blood pressure response to salt intake: several genotype have been identified and most of these influence the renin-angiotensin-aldosterone axis or renal salt handling);
  • interactions among environmental and genetic factors.

Secondary hypertension

It is caused by other diseases, usually endocrine.

Risk factors for hypertension

Hypertension
Fig. 1 – Effects of High Blood Pressure

It is the most common public health problem in developed countries.
In USA as many as 50 million adult people, one out of four of the adult population, have the disease, and its worldwide prevalence is projected to increase from approximately 1.0 billion in 2000 to 1.5 billion by 2025.
It is a major, independent risk factor for cardiovascular disease (CVD, and the chief risk factor for stroke (accounted for about 62% of strokes).
It’s often called “the silent killer” because it can be asymptomatic for many years, and people suffering of this problem can have a sudden fatal heart attack.
Elevated blood pressure levels are a common and important risk factor also for kidney failure.
Above-optimal blood pressure levels, not yet in the hypertensive range or prehypertensive, also confer excess cardiovascular disease risk, as it is shown by the fact that almost a third of blood pressure-related deaths from coronary heart disease are estimated to occur in no hypertensive individuals with systolic blood pressure levels of 120 to 139 mm Hg or diastolic blood pressure levels of 80 to 89 mm Hg (approximately 31% of the general population have blood pressure in the no hypertensive, yet above optimal blood pressure range).
This means that the risk of cardiovascular disease increases throughout the range of blood pressure, from 115/75 mm Hg, so including the prehypertensive range.
More than half of American adult population is included, considering hypertensive together with prehypertensive. Prehypertensive people have a high risk (90%) of eventually developing hypertension but this transition is not inevitable.

Note: on average, blacks have higher blood pressure levels than non-blacks and an increased risk of blood pressure-related complications, particularly stroke and kidney failure. On the other hands, they achieve greater blood pressure reduction than non-blacks from several non-pharmacological therapies (see below).

But, hypertension is one of the major modifiable risk factors for cardiovascular disease.

Age related hypertension

The prevalence of the disease rises with increasing age: over half the adult population older than 60 years has hypertension.
The age-related risk of high blood pressure is a function of life-style variables rather than just aging. Weight gain, low physical activity, excess in salt, fats and saturated fats, cholesterol and alcohol intakes and low intakes of fresh seasonal fruit and vegetable are responsible for much of the rise in blood pressure levels seen with age.
Studies on vegetarians living in industrialized countries have shown that such dietary habits are associated with a markedly lower blood pressure levels compared with non-vegetarians; furthermore there is a lower age-related rise in blood pressure.

Hypertension and childhood

According to a study by a team research of Johns Hopkins University (USA), prevention of hypertension begins in childhood.
A meta-analyses conducted on studies from diverse population, examining the tracking of blood pressure levels from childhood to adulthood published between January 1970 and July 2006, have shown that childhood blood pressure is associated with blood pressure in later life and elevated childhood blood pressure is likely to help predict adult hypertension (note: recent studies show that increased blood pressure levels among children is related to the growing obesity epidemic).

Lifestyle modifications to prevent hypertension

Hypertension
Fig. 2 – Plant Foods and Dairy Products

In the last two decades a downward trend of blood pressure has been documented in the USA; the adoption of healthier lifestyle have contributed to this trend and it has given diet a prominent role Moreover, between 1980 and 2000 also the rate of death from coronary heart disease was halved and approximately half the decrease was attributable to changes in major risk factors including reductions in total cholesterol, systolic blood pressure levels (20%), smoking and physical inactivity).

Recommended lifestyle modifications, that effectively lower blood pressure levels, are:

Therefore, adopt a healthy lifestyles is the critical factor!!!
These changes need not be made one at a time: the best results are achieved when they are together as shown by two trials in which multicomponent interventions substantially lowered blood pressure levels in hypertensive and nonhypertensive participants.
For all these reasons it is believed that hypertension is preventable.

References

Appel L.J., Brands M.W., Daniels S.R., Karanja N., Elmer P.J. and Sacks F.M. Dietary approaches to prevent and treat HTN: a scientific statement from the American Heart Association. Hypertension 2006;47:296-08 [Abstract]

Bibbins-Domingo K., Chertow G.M., Coxson P.G., Moran A., Lightwood J.M., Pletcher M.J., and Goldman L. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med 2010;362:590-9 [Abstract]

Chen X. and Wang Y. Tracking of blood pressure from childhood to adulthood. A systematic review and meta-regression analysis. Circulation 2008;117:3171-80 [Abstract]

Ford E.S., Ajani U.A., Croft J.B. et al. Explaining the decrease in U.S. deaths from coronary disease, 1980-2000. N Engl J Med 2007;356:2388-98 [Abstract]

Geleijnse J.M., Witteman J.C., den Breeijen J.H., Hofman A., de Jong P., Pols H.A. and Grobbee D.E. Dietary electrolyte intake and blood pressure in older subjects: the Rotterdam Study. J Hyperten 1996;14:73741 [Abstract]

Holmes E., Loo R.L., Stamler J., Bictash M., Yap I.K.S., Chan Q., Ebbels T., De Iorio M., Brown I.J., Veselkov K.A., Daviglus M.L., Kesteloot H., Ueshima H., Zhao L., Nicholson J.K. and Elliott P. Human metabolic phenotype diversity and its association with diet and blood pressure. Nature 2008;453:396-400 [First paragraph]

Mahan LK, Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Pickering T.G. New guidelines on diet and blood pressure. Hypertension 2006;47:135-6 [Full text]

Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Writing Group of the PREMIER Collaborative Research Group. Effects of comprehensive lifestyle modification on blood pressure control: main results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]

World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/ISH statement on management of HTN. Guidelines and recommendations. J Hyperten 2003;21:1983-92. [Abstract]

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