Introduction

Nocturia, or waking to urinate during sleep, plagues many, especially elderly people. Once deemed harmless, new evidence links it to cardiovascular disease (CVD). This article explores that connection, examining recent research on underlying mechanisms and clinical impacts. Though often dismissed as age-related, nocturia may signal an early CVD risk. Understanding this relationship could improve diagnosis and treatment for both conditions. We will delve into studies revealing how nocturia and heart health intertwined. Potentially pathophysiological reshaping our approach to these common issues.

Epidemiology of nocturia

Nocturia is a common condition. Its prevalence rate increases with age in both sexes, males and females, and its prevalence in people assigned female at birth (AFAB)  in their twenties to thirties was 4.4%–18%, while in their seventh and eighth decades, it was 28.3%–61.5%. In people assigned male at birth (AMAB) groups of the same age, it increased from 2.0%–16.6% to 29.0%–59.3%, respectively. Although considered predominant in people AMAB, recent cross-sectional surveys on participants from five countries show higher ratios in people AFAB (54.5%) than people AMAB (48.6%). Numerous potential factors have implicit nocturia, such as sleep disorders, bladder outlet obstruction, overactive bladder syndrome (OAB), sleep syndrome, and fractures due to slipping, among others, which makes a close assessment of this condition highly needed to define a better cure.²

Overview of cardiovascular disease

Heart disease, the leading cause of death globally, originates from different underlying factors that impact the heart and the blood vessels. Some examples are heart failure, hypertension, cerebrovascular disease, rheumatic heart disease, inflammation, endothelial dysfunction, and coronary artery disease. Genetics, environment, and lifestyle are also influencing factors. This dangerous combination drives the spread of cardiovascular disease, posing a challenge to worldwide health initiatives.³ 

Pathophysiological mechanisms linking nocturia and cardiovascular disease

Nocturia’s link with cardiovascular disease stems from four main mechanisms. These mechanisms are illustrated simply here below:

Fluid redistribution

Left atrial enlargement (LAE) stands out as the most significant cardiac abnormality associated with nocturia. This connection has been documented earlier through two possible mechanisms.

Left atrial enlargement LAE boosts the atrial natriuretic peptide (ANP) levels, triggering diuresis and natriuresis by raising renal plasma flow, glomerular filtration rate (GFR), and sodium excretion.

LAE causes cardiac structural changes and causes sodium and water retention in the extracellular space. When sleeping in a lying-down position, the redistribution of fluids from edematous legs causes nocturnal polyurea.⁴  

Sympathetic nervous system activation

Studies suggest that autonomic nervous system (ANS) dysregulation is related to the overactivity of the sympathetic and parasympathetic systems. The increase in sympathetic system tone by default causes an elevation of blood pressure and heart rate and an increase in nocturia.⁵

Sleep apnea and hypoxia

Among patients with nocturia, sleep apnea-repeated pauses in breathing during sleep is a common comorbidity. 

Obstructive sleep apnea (OSA), the most common type of this sleep disorder, disrupts the cardiovascular system (CVS). It causes blood gas abnormalities (reduced oxygen and increased carbon dioxide levels in the blood), frequent arousals (frequent awakening from sleep due to breathing difficulty), changes in the autonomic nervous system (ANS) (reduced parasympathetic and increased sympathetic activities), and additionally, creating a negative pressure swing when exerting effort to breathe against a closed airway. These effects cause nocturia.^6,7

Inflammation and endothelial dysfunction

Interrupted and insufficient sleep resulting from nocturia leads to oxidative stress, leading to vascular inflammation. Vascular inflammation is a precursor to CVD. Insufficient sleep also leads to the release of pro-inflammatory cytokines, which also impact CVD.

The integrity of the endothelium (the inner lining of the blood vessels) is crucial for cardiovascular health. Both nocturnal hypoxia and increased oxidative stress contribute to endothelial dysfunction.⁸

Clinical evidence supporting the association

Many epidemiological studies and clinical trials have been conducted to investigate the relationship between nocturia and cardiovascular diseases. Recent research findings reveal the following: 

Epidemiological studies

A cohort study with over 20,000 participants found that individuals with nocturia had a higher risk of developing coronary artery disease.⁹ On the other hand, a longitudinal study found that nocturia was an independent predictor of heart failure in the elderly.¹⁰

Randomised control trials (RCTs)

In RCTs on people AMAB aged 35–49 with uncontrolled blood pressure and having medical treatment, researchers discovered that there is a link between the control of the blood pressure through treatment and the decrease in nocturia.¹¹ 

Implications for clinical practice

Realising nocturia as a potential early warning of cardiovascular disease has important implications for clinical practice. Swift identification and treatment of nocturia could help in the health improvement and outcomes of CVD patients.

Screening and assessment

Clinicians shouldn’t underestimate nocturia as asymptomatic of serious CVD, so they should ask suspected patients with CVD to perform a thorough assessment, including a physical examination, a detailed medical history check, and relevant diagnostic tests.¹² 

Integrated management approaches

This includes improving fluid management, addressing comorbid conditions such as blood hypertension and diabetes, and implementing lifestyle modifications. ¹²

Patient education and self-management

It is essential to inform patients about the potential correlation between nocturia and cardiovascular disease. Encouraging patients to monitor their symptoms and adhere to treatment can improve their health outcomes and well-being.

Future research directions

Despite the several studies, research, and trials conducted to prove the evidence of the link between nocturia and cardiovascular disease, several gaps still exist, and future research should focus on:

• Mechanistic studies:Through advanced imaging and analysing biomarkers (specific molecules or proteins)¹³
• Longitudinal studies:Long-term studies are essential to understand if nocturia causes cardiovascular disease or vice versa. These studies can also help to identify high-risk groups and target interventions¹⁴
• Intervention trials: Randomised control trials to test different ways of treating nocturia and how they impact heart health by looking for various approaches, including medications and lifestyle changes.¹⁴

FAQs

Is nocturnal heart failure left or right?

Both types can co-exist

What is nocturia heart failure treatment?

Medications such as diuretics, ACE inhibitors, beta-blockers, lifestyle changes, monitoring fluid and salt intake, surgical options, or heart transplantation in severe cases. 

What is the most common cause of nocturia?

Nocturnal polyurea, ageing, consuming caffeinated or alcoholic drinks and drinking water before bedtime, medication side effects, menopause, and pregnancy.

What is the best sleeping position for nocturia?

The left-side position allows gravity to empty the bladder more efficiently.

Why does heart failure cause decreased urine output?

When the heart is unable to pump forcefully, the amount of blood it ejects with each contraction drops. This reduces the amount of blood that passes to the kidneys, causing urine and waste output to drop.

Summary

Nocturia, the need to wake up at night to urinate, is a frequently underestimated condition that might indicate early cardiovascular problems. Recognising the intricate connection between nocturia and cardiovascular health can lead to earlier detection and better management of both issues, potentially improving overall patient health. As research progresses, new diagnostic tools and preventive measures are expected to enhance our ability to identify and address nocturia more effectively. Addressing this significant public health concern requires ongoing research and a collaborative healthcare approach.