Physiological rhythms of blood pressure: Implications for health from age, season, and diurnal fluctuations

Before menopause, women's blood pressure is slightly lower than that of men of the same age, but it rises significantly after menopause. Blood pressure can also fluctuate under different physiological conditions. For example, blood pressure rises slightly after meals as the stomach and intestines begin digesting food. Blood pressure decreases during the first few hours of sleep and rises during dreaming. Excitement and fear also increase blood pressure. Changes in weather temperature affect blood pressure. Doctors have observed that blood pressure is often higher in winter than in summer, regardless of whether one has normal or high blood pressure. Therefore, during the cold winter months, people should choose appropriate warm clothing and adjust it according to weather changes to prevent high blood pressure. Keeping the head warm is especially important. Blood pressure also fluctuates physiologically throughout the 24-hour day. For those with a normal lifestyle, blood pressure is highest around 9 or 10 am, gradually decreases, and reaches its lowest point during sleep. The maximum difference in blood pressure fluctuation over 24 hours can reach 40 mmHg. Blood pressure can rise by 20 mmHg upon waking and further increase after getting up and moving around, which may be a major reason why sudden death from coronary heart disease often occurs in the early morning.

Knowing the fluctuations in blood pressure, your blood pressure will vary throughout the 24 hours of the day. For example, it might be 120/80 mmHg in the morning, 110/70 mmHg at noon, 105/75 mmHg in the evening, and 95/65 mmHg at night. These values ​​are all within the normal range, and normal blood pressure fluctuations maintain the body's physiological needs. Blood pressure values ​​reflect whether your body is in a healthy, diseased, or sub-healthy state. Therefore, no matter how busy or tired you are, you should check your blood pressure regularly to understand your health status. As mentioned earlier, blood pressure is formed by two factors: the pumping action of the heart and the resistance of blood vessels. Therefore, problems in either aspect will cause abnormal blood pressure. In the course of life, the continuous beating of the heart (contraction and relaxation) is the manifestation of the heart as the pumping force for blood. The myocardium shares similarities with other muscles in the body; the contraction response of myocardial cells is also triggered by the "excitation-coupling" of the nervous system on the myocardial membrane. This is like the fuse on a firecracker; only when it is lit and burns to a certain point will the firecracker explode. The difference lies in the fact that the muscles in a person's arms and legs (skeletal muscles) only move under the influence of nerve impulses from the somatic efferent nerve fibers that control them. The heartbeat, however, is generated and conducted by the heart's specialized conduction system, transmitting "excitation and contraction"—this excitation and contraction is the heartbeat.

Therefore, we also call the cardiac muscle "involuntary muscle." Involuntary muscle means that the heart doesn't beat when you tell it to; it doesn't stop when you tell it not to. It's not under conscious control. However, if the heart itself or its specialized conduction system malfunctions, it can weaken the heart's ejection function, leading to changes in blood pressure. Tip: Regularly measuring blood pressure can indirectly indicate whether heart function is normal. Regarding vascular resistance, first understand the composition of blood vessels. Blood vessels are composed of four main components: endothelium, elastic fibers, smooth muscle, and collagen fibers. Based on their location and function, they are divided into arteries, capillaries, and veins. To adapt to different functions, the walls, diameters, and contents of the four main components of these blood vessels vary. Under various physiological conditions (sleep, exercise, excitement, tension, etc.), the body regulates the diameter of blood vessels in different organs, altering blood flow resistance to ensure that blood distribution among organs meets the needs of the entire body. Medical research has found that anything that changes vascular resistance can affect blood pressure. For example, if the heart's ejection volume remains unchanged, but vascular resistance increases, blood pressure rises. High diastolic blood pressure is likely a sign of vascular problems, as it reflects high vascular resistance. If diastolic pressure is significantly higher than systolic pressure, a fundus examination is recommended, as the retinal arteries may show signs of arteriosclerosis, which reflects systemic arteriosclerosis.

Therefore, middle-aged people should have their fundus checked periodically. Additionally, a blood rheology test can be performed to check if blood viscosity is higher than normal. High blood viscosity also increases vascular resistance, leading to elevated diastolic pressure. Some might say, "My heart, blood, and blood vessels all have some problems, but I don't feel any discomfort." This could mean two things: either the condition is mild, or the body is in a compensatory phase. The "compensatory period" refers to a time when the function or structure of an organ in our body malfunctions. Because these problems are not particularly serious, the healthy parts of the original organ or other organs compensate for its function. The "compensatory period" is limited in time. Beyond a certain time and range, the "compensatory period" becomes the "decompensatory period," and the problem becomes serious in the "decompensatory period."