Simply put, blood pressure is defined as the pressure exerted by the blood on blood vessels in the body. If you have ever noticed, two readings are recorded when noting the person's blood pressure: systolic and diastolic pressure. The diastolic pressure, i.e., the lower of the two readings recorded, is the pressure that is present in the walls of arteries when the heart is in a relaxed state in between two consecutive contractions. It is said to be as important as the systolic blood pressure reading. In a broad sense, the numerous factors that affect it are grouped into two categories: physiologic factors and pathologic factors.
These include, first of all, the posture of a person and the various receptors that are responsible for sensing pressure, which are referred to as baroreceptors. When we suddenly stand up after being in a sitting or lying position for a long time, we tend to feel lightheaded or dizzy. This happens because the diastolic blood pressure does not manage to push back enough blood to the brain in time. Baroreceptors are pressure receptors that are present throughout the body, which send signals to the heart when there is a sudden drop in the blood pressure. In the event of sudden drop, these receptors stimulate the heart and brain to increase the diastolic pressure.
Yet another physiological factor that can come into play is aging. With age, the elasticity of arteries decreases considerably, and that causes the diastolic pressure to increase. Genetics is also said to play an important role in these readings, although this cannot be said to be a direct and sole major factor as such.
Many of these factors are the same as those of high systolic blood pressure. One of the main reasons of diastolic hypertension is sedentary lifestyle. Lack of adequate amount of physical activity, often coupled with a bad and unhealthy diet leads to obesity, which is said to be one of the leading causes of many serious diseases and conditions. Often due to obesity and an increase in the amount of cholesterol in the body, there is deposition of plaque in the inner walls of arteries. This doesn't just compromise the elasticity of the arteries, but also narrows their lumen. This leads to lesser space for blood flow, which translates into an increase in the diastolic blood pressure and often, the systolic blood pressure as well.
Another factor that is said to be responsible is addiction. Bad habits like smoking and drinking are known to adversely affect the functioning of heart. These habits lead to problems in the circulatory system, which invariably affects the functioning of every other system in the body. Even underlying diseases, like diabetes or kidney problems, lower the diastolic blood pressure. So do hormonal fluctuations in the body and certain medication.
Malnutrition diseases and deficiency of certain factors in the diet, such as inadequate amount of sodium, can decrease the diastolic pressure. The same can also be attributed to lack of vitamins as well as dehydration. Other factors which lower blood pressure include excessive blood loss, certain blood diseases, blood infection, etc.
Blood pressure can be kept in check by controlling some of these factors by following a healthy lifestyle. High diastolic blood pressure is said to be an indicator of possible heart diseases, so it is important to ensure that this reading stays within the desired range.