Introduction:
Hypertension (increased blood pressure) is considered a leading cause of kidney-related disorders as it can damage the filters and blood vessels in the kidney and make the waste excretion process very difficult. A new study found that increased urination at night may be linked to hypertension and high salt intake. This article explains the link between hypertension and increased urine output during the night.
What Is Nocturia?
Nocturia is a condition that causes people to wake up during the night as they need to urinate. The most common causes of frequent urination at night include high fluid intake, sleep disorders, kidney infection, diabetes, neurological disorder, overactive bladder, and bladder obstruction. People without nocturia may sleep without urinating for up to eight hours, but some people may need to wake up once during the night for urination, which can be considered within normal limits. But people with nocturia may get up to two to six times for visits to the toilet during the night. Pregnant women and people with other health disorders like heart, kidney, liver failure, and diabetes may also have nocturia.
Nocturia is a common sign of old age, as their bodies produce less antidiuretic hormone that allows them to retain fluid; also, they tend to lose holding capacity, along with other medical issues that impact the bladder, leading to more urine production during the night. People between the ages of 55 and 84 have reported that they experienced nocturia for at least a few nights per week, as per a poll conducted by National Sleep Foundation.
How Does Hypertension Affect the Kidney?
Hypertension occurs when the force of the blood pushing through the blood vessels is consistently too high. When the blood vessels are narrow, mostly due to fatty deposits on the walls of the blood vessels, it creates more resistance to blood flow and raises blood pressure. Hypertension usually occurs gradually and causes damage to many internal organs like the heart, lungs, kidneys, and brain. Hypertension is the second leading cause of kidney failure. This is because the kidneys and circulatory system depend on each other for overall good health. The main function of the kidneys is to filter wastes and fluid extraction from the blood with the help of blood vessels. If these blood vessels get damaged, it causes damage to the kidney.
The nephrons in the kidneys are densely packed with a network of blood vessels, and so an increased amount of blood flows through them. Persistent uncontrolled hypertension causes the narrowing of the arteries situated around the kidneys, which can weaken or harden gradually over time, and may not be able to deliver enough blood to the kidney tissue. When the arteries are damaged, the nephron (small, finger-like nephrons that filter the blood) does not receive enough oxygen and nutrients. So the kidney will not be able to filter blood and regulate the hormones, acids, fluid, and salts in the body.
If the kidney is damaged, it will be impaired in regulating blood pressure. Healthy kidneys respond to aldosterone (a hormone that regulates blood pressure) produced in the adrenal glands and help in regulating the body’s blood pressure. Uncontrolled hypertension and kidney damage can contribute to a negative spiral and stop the functioning of the kidneys leading to total kidney failure.
Does Hypertension Cause Increase Urine Output?
Many studies have been conducted to prove the relationship between hypertension and increased urine output during the night (nocturia). Research enrolled 3,749 residents of Watari in Japan who underwent an annual health check in 2017, and the team gathered information using questionnaires about their blood pressure levels and nocturia. The data collected showed that getting up at night to urinate was linked with a 40 percent greater chance of increased blood pressure. Also, the hypertension risk rose promptly as there was an increase in the number of nocturia events. Experts say the results do not prove any relationship between hypertension and nocturia. The relationship may be influenced by several other factors, including salt intake, lifestyle, ethnicity, and genetic background. Hypertension is more in Japan, as the salt intake is more in Japan when compared to other countries. Approximately 10 grams per day is Japan's average salt intake, which is more than double the worldwide average salt intake. This excessive salt intake may also be a reason.
In another study, seventy-seven patients who were being treated for hypertension at a Japanese clinic were enrolled. A questionnaire was given to each person to collect details about the number of times they urinated during the day and at night, and their blood pressure was measured at home soon after they woke up in the morning and just before going to bed at night. The patients were divided into many groups a sustained hypertension group, a masked hypertension group, a white coat hypertension group, and a normotension group depending on the morning to evening (ME) average blood pressure calculated with the average of the systolic blood pressure measured at home during the morning and at night. The study showed that daytime urinations were lower, and nighttime urinations were significantly larger in people with increased hypertension in the morning. Additionally, the percentage of patients with more nighttime urination was also in the morning hypertension group. These findings suggest that early morning elevation of blood pressure has an influence on the frequency of daytime and nighttime urination.
Hypertension during the day would decrease renal blood flow due to increased renal arterial resistance. Thus, there will be less daytime urine production. During the night, the renal arterial resistance decreases due to decreased catecholamines production at night, so there is an increase in renal blood flow, allowing urine production to increase at night to excrete water stored during the daytime. Also, water accumulated in the extracellular compartment during the daytime may enter the intravascular compartment at night, thus raising the circulating blood volume and certain hormones to promote urine production.
Conclusion:
Hypertension is one of the leading causes of kidney damage. Increased urination at night, decreased urination during the day, and edema in the legs are some common symptoms of kidney damage. The relation between increased urine output the night and hypertension was found in a study conducted in Japan. It is necessary to maintain blood pressure within normal limits as it can cause damage not only to kidneys but also to other organs like the heart, brain, eyes, and lungs. Always have a regular check with a physician to make sure that the blood pressure is under control. If the blood pressure is high (hypertension) one should seek medical assistance to get blood pressure under control.
