Blood pressure (BP) simply refers to the 'pressure' that 'blood' exerts to the vessel (tubes that carry blood) wall. Here is an analogy: water flowing through a tube exerts pressure on its walls. There are 2 basic concepts to understand. First, blood flow through the vessels is dynamic in nature. It increases when heart contracts, and decreases when heart relaxes. Due to this, blood pressure also increases during heart contraction and vice versa. The peak is labelled as 'systolic' pressure (sBP) and nadir is labelled as 'diastolic' (dBP). Second,
blood vessels are made up of a special type of muscle which enables them to expand and relax to accommodate
change in blood flow. This property is called vessel compliance, and it helps absorb some of the impact of dynamic blood flow. If vessel compliance decreases (with age), similar change in blood flow produces higher fluctuation in blood pressure. This explains why elderly people typically have high sBP and low dBP.
Blood needs to flow with a certain pressure in order to overcome resistance of a body organ. Drop in pressure leads to decreased blood flow through an organ (for e.g. Kidneys). Human organs typically under-perform due to lack of blood supply. Up to a certain extent, such organ dysfunction is reversible if optimal blood flow is restored. But, if blood flow compromise is severe or prolonged, permanent damage to the organ may ensue. On the other hand, high blood pressure can cause damage 2 ways. Immediate surge in BP leads to physical damage that percolates to the cellular level. Such damage is typically severe and may have a long lasting effect. Long term uncontrolled BP, even with modest increase, leads to structural changes in organs (adapting to high pressures). These changes effect almost every organ, and the damage is permanent. Because human body has significant reserve, organs with moderate damage may still function reasonably and not cause any obvious symptoms.
Normal sBP is less than 120, dBP is less than 80. For organs to get optimal blood, sBP of more than 90 is typically sufficient (there are few exceptions). People with sBP between 90 and 120 typically feel fine and this rarely is of any concern. sBP lower than 90 may create signs/symptoms of organ hypo-perfusion. BP higher than 120/80 should be addressed to prevent long-term complications. sBP more than 180 can cause acute illness and needs to be managed urgently.
Hypertension is when BP is more than 120/80. It is managed with lifestyle modifications like weight loss, routine exercise, low salt intake, low emotional stress, yoga etc. Medications are brought in if lifestyle modifications alone are insufficient, or if BP is high enough that lifestyle modifications in itself is unlikely to be very effective. Choice of medications is highly individualized and one should refer to their treating physicians.
One should look for other causes of high blood pressure as well. Certain organ dysfunction can lead to hypertension (condition is called 'secondary hypertension'), for e.g Kidneys, Thyroid, Adrenals etc. Medications like steroids, pain killers can also contribute to high blood pressure. Night-time snoring is associated with a clinical condition called "Obstructive Sleep Apnea" (OSA). People with OSA typically have difficulty controlling their BP as well.
Hypertension, without any identifiable cause, typically stays lifelong which means BP reduction measures in some form need to be taken for rest of the life. This can be in the form of lifestyle modifications alone or a combination of lifestyle with some medications. With current pharmaceutical advancements, medicines these days are very well tolerated with acceptable side effect profile. Also, many hypertension medications are shared with that of heart or diabetes management. In essence, few hypertension medications work on heart and/or kidneys as well.
I am sure this article won't cover all the questions you may have. Feel free to drop in any question or comment you have and I will gladly answer those.