Blood pressure is an important indicator of a person’s general state of health. This is why it is so important to check it regularly, especially in people over 35 years of age. Changes in blood pressure, either above or below the normal range, may have serious implications on an individual’s health.
What is Blood Pressure?
Basically, blood pressure is the pressure (defined as flow/area) that the blood exerts on the walls of arteries as it flows round the body. Two numbers express a blood pressure reading: systolic blood pressure (SBP) is the pressure exerted when the heart contracts i.e. when it beats to pump blood out. And the diastolic blood pressure (DBP) is the pressure between beats. The combination of both values of blood pressure (expressed as the ratio systolic/diastolic) make up your blood pressure reading.
According to Chobanian et al (2003) a normal blood pressure reading should be 90 – 119 for the systolic and 60 – 79 for the diastolic. Then, a normal healthy range would read as 90-119/60-79. Blood pressure readings above those normal values are considered high blood pressure, also called hypertension. In the prehypertension group people may have values of blood pressure just slightly above the normal (120-139/80-89). People with blood pressure above 140/89 are considered to have hypertension. The risk of cardiovascular disease increases as the blood pressure increases.
High Blood Pressure Causes
There are many things that may cause high blood pressure. Hypertension can be divided in two types: essential (primary) or secondary. In essential hypertension there is no known, specific, identifiable medical cause that might explain a patient’s high blood pressure while in secondary hypertension (the hypertension is secondary to another condition) there is a specific medical cause. Among the possible contributory causes of primary blood pressure are obesity, age, sodium sensitivity, insulin resistance, and genetics. Causes for secondary hypertension are varied and identifiable such kidney disease, tumors, drugs, and pregnancy.
Genetics of High Blood Pressure
Dickson and Sigmund (2006) showed that more than 50 genes are involved in the determination of high blood pressure. The genetics of hypertension is complex and poorly understood. However, according to the authors certain specific genes, such as the angiotensinogen (AGT) gene, seem to have a direct effect: the more it is expressed the higher the blood pressure.
In a more recent study, published in the journal Nature (May 2009), many single-nucleotide polymorphisms (SNPs) were shown to be associated with systolic blood pressure, diastolic blood pressure, and hypertension. Among these were: the ATP2B1 genes which code for a cell membrane enzyme (PMCA1) involved in calcium transport - and the gene CACNB2, which codes for a part of a calcium channel protein in the cell membrane.
Chobanian et al (2003). “Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.” Hypertension. 2003 Dec;42(6):1206-52.
Dickson and Sigmund (2006). Genetic basis of hypertension: revisiting angiotensinogen”. Hypertension 48 (1): 14–20.