Role of atrial natriuretic peptide in nocturnal polyuria in elderly males

The prevalence and predictive factors of nocturnal polyuria in Japanese patients with nocturia: a multicentral retrospective cohort study

The aims of this study were to determine the prevalence and predictors of nocturnal polyuria (NP) in Japanese patients. This multicentral, observational study enrolled patients with the chief complaint of nocturia at 17 Japanese institutions between January 2018 and December 2022. The frequency of daily voiding and volume of urination were evaluated using bladder diaries. NP was diagnosed in patients with an NP index of > 33%. The primary endpoint was NP prevalence in patients with nocturia. The secondary endpoints were the prevalence of NP according to sex and age and the identification of factors predicting NP. This study analyzed 875 eligible patients. NP was present in 590 (67.4%) patients, with prevalence rates of 66.6% and 70.0% in men and women, respectively. Age ≥ 78 years, body mass index (BMI) < 23.0 kg/m2, and patients with ischemic heart or cerebrovascular disease were significant predictors of NP (P < 0.001, P < 0.001, P = 0.014, P = 0.016, respectively). This is the first large multicenter study to investigate the prevalence of NP in Japanese patients with nocturia. NP has a prevalence of 67.4%. Significant predictors of NP include age, BMI, and cardiovascular disease.

'Nocturomics': transition to omics-driven biomarkers of nocturia, a systematic review and future prospects

OBJECTIVE

To systematically review studies that investigated different biomarkers of nocturia, including omics-driven biomarkers or 'Nocturomics'.

MATERIALS AND METHODS

PubMed® , Scopus® , and Embase® were searched systematically in May 2022 for research papers on biomarkers in physiological fluids and tissues from patients with nocturia. A distinction was made between biomarkers or candidates discovered by omics techniques, referred to as omics-driven biomarkers, and classical biomarkers, measured by standard laboratory techniques and mostly thought from pathophysiological hypothesis.

RESULTS

A total of 13 studies with 18 881 patients in total were included, eight of which focused on classical biomarkers including: atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), C-reactive protein (CRP), aldosterone, and melatonin. Five were 'Nocturomics', including one that assessed the microbiome and identified 27 faecal and eight urinary bacteria correlated with nocturia; and four studies that identified candidate metabolomic biomarkers, including fatty acid metabolites, serotonin, glycerol, lauric acid, thiaproline, and imidazolelactic acid among others. To date, no biomarker is recommended in clinical practice. Nocturomics are in an embryonic phase of conception but are developing quickly. Although candidate biomarkers are being identified, none of them are yet validated on a large sample, although some preclinical studies have shown a probable role of fatty acid metabolites as a possible biomarker of circadian rhythm and chronotherapy.

CONCLUSION

Further research is needed to validate biomarkers for nocturia within the framework of a diagnostic and therapeutic precision medicine perspective. We hope this study provides a summary of the current biomarker discoveries associated with nocturia and details future prospects for omics-driven biomarkers.

Nocturia independently predicts left ventricular hypertrophy and left atrial enlargement among patients with cardiac symptoms

Nocturia can be caused by urological disorders and systemic diseases, including heart diseases. We aimed to investigate the relationship between nocturia and structural abnormalities on echocardiography. Adult patients who underwent echocardiography for cardiac symptoms or heart murmur or had a history of structural heart disease were included. The voiding times during sleep hours were collected prospectively. Univariate and multivariate analyses were performed to evaluate the predictive value of bothersome nocturia (nocturia ≥ 2) on echocardiographic abnormalities. Of 299 patients, 182 (60.9%) reported bothersome nocturia. In patients aged ≥ 65 years, hypertension and left atrial enlargement (LAE) were associated with higher occurrences of bothersome nocturia. On multivariate analysis, bothersome nocturia was a predictive factor of LAE (odds ratio [OR] 2.453, 95% confidence interval [CI] 1.363–4.416, p = 0.003). Moreover, bothersome nocturia could predict both LAE and left ventricular hypertrophy (LVH) (OR 2.285, 95% CI 1.151–4.536, p = 0.018; OR 2.056, 95% CI 1.025–4.124, p = 0.043) in the elderly. Older age, hypertension, and LAE were risk factors for bothersome nocturia. Moreover, bothersome nocturia was predictive of LAE and LVH in the elderly. Patients with bothersome nocturia without other significant lower urinary tract symptoms should be referred to cardiologists.

Pharmacologic management of nocturnal polyuria: a contemporary assessment of efficacy, safety, and progress toward individualized treatment

This narrative review synthesizes current evidence on the medical management of nocturnal polyuria, including antidiuretic replacement therapy as well as other emerging modalities, with particular emphasis on areas of active investigation and future research directions. Relative to earlier formulations, the pharmacological profiles of novel desmopressin acetate nasal spray and orally disintegrating tablet formulations appear favorable in optimizing the balance between efficacy and safety. Additionally, several highly selective small-molecule arginine vasopressin 2 receptor agonists are under active development, while appropriately timed short-acting diuretics, pharmacotherapy for hypertension, nonsteroidal anti-inflammatory drugs, and sex hormone replacement therapy are also a focal point of extensive ongoing nocturnal polyuria research. Emerging laboratory technologies now make feasible a sub-stratification of nocturnal polyuria patients into substrate-based phenotypes for individualized treatment. An increasingly refined understanding of the pathogenesis of nocturnal polyuria, and arginine vasopressin dysregulation in particular, has also introduced new opportunities for point-of-care testing in patients with nocturnal polyuria.

Comparison of nocturia response to desmopressin treatment in elderly men with and without nocturnal polyuria in real-life practice

OBJECTIVES

To evaluate the safety and efficacy of low-dose desmopressin in elderly men with and without nocturnal polyuria (NP) in real-life practice.

METHODS

Patients with lower urinary tract symptoms (LUTS)/ benign prostate hyperplasia (BPH) who were≧ 65 years old with refractory nocturia were enrolled in this study. We retrospectively analysed elderly men treated with adding desmopressin to current medications for nocturia according to category of the baseline nocturnal urine volume. The 48-h frequency volume chart (FVC), International Prostate Symptom Score (IPSS) and quality of life (QoL) were initially assessed and re-evaluated 12 weeks later. Serum sodium level was checked 1 week, 4 weeks, and 12 weeks after initiation of desmopressin therapy or suspected hyponatremia event. The mean change in numbers of nocturnal voids was evaluated for efficacy of treatment.

RESULTS

A total of 136 patients were included with 55 in non-NP group and 81 in NP group. Hypertension was more common in NP group in regard of comorbidities. During treatment period, there were significant reductions of nocturnal voids from 4.22 ± 1.38 to 2.31 ± 0.98 (p < 0.001) in non-NP group and from 4.52 ± 1.23 to 2.07 ± 0.89 (p < 0.001) in NP group. The reduction in nocturnal voids was more significant in NP group (2.44 ± 1.15 vs. 1.91 ± 1.48, p = 0.003). The mean decrease in serum sodium levels were 3.89 ± 1.22 mmol/l (p < 0.001) in non-NP group and 4.69 ± 3.5 mmol/l (p < 0.001) in NP group at the extreme value.

CONCLUSIONS

Long-term treatment with low-dose desmopressin is safe and effective for nocturia with or without NP in elderly patients with LUTS/BPH during real-life practice. Patients should be well informed about the disease and are closely followed.

Central hemodynamics, vascular stiffness, and nocturia in patients with type 2 diabetes

Recently, studies have shown that the presence of nocturia may not be a benign condition and related with systemic illness and mortality. Elevated blood pressure (BP) was another factor related with nocturia. Type 2 diabetes mellitus (T2DM) is also associated with nocturia. It is now clear that, apart from peripheral BP, central hemodynamic parameters are important for cardiovascular prognosis. However, no previous study in the literature examined the relationship between nocturia and central hemodynamic parameters in patients with T2DM. The current study was designed to examine these relationships. Nocturia was defined as two or more voids per night. Central hemodynamic parameters were assessed from ambulatory BP measurements. In addition to routine biochemistry, 24-h urine collection was performed to measure protein, albumin, and sodium excretion. 158 patients (52.3%) had T2DM and 144 (47.7%) did not have T2DM (control group). The presence of T2DM was independently related with nocturia. Both in whole group and in T2DM patients, most of the hemodynamic parameters are higher in patients with nocturia compared to patients without nocturia. Among patients with T2DM, nocturia was associated with augmentation index and pulse wave velocity. In conclusion, central hemodynamic parameters and markers of vascular stiffness may be related with nocturia in patients with T2DM.

Nocturia in arterial hypertension: a prevalent, underreported, and sometimes underestimated association

Nocturia is a risk factor for morbidity and mortality but is frequently overlooked and underreported by patients and unrecognized by physicians. Epidemiologic studies reported that nocturnal voiding is associated not only with aging and benign prostatic hyperplasia, but also with many other clinical conditions. The majority of epidemiologic studies reported a significant relationship between nocturia and hypertension. However, the cause-and-effect relationship between them has not been established. Some physiopathological changes in hypertension are conducive to result in nocturia. These include the effects of hypertension on glomerular filtration and tubular transport, resetting of the kidney pressure-natriuresis relationship, atrial stretch and release of atrial natriuretic peptide when congestive heart failure complicates hypertension, and peripheral edema. Another link between hypertension and nocturia is obstructive sleep apnea. Furthermore, some evidence supports the relationship between nondipping behavior of blood pressure and an increased prevalence of nocturia. The use of some classes of antihypertensive agents may result in nocturia. The present review aims to provide a comprehensive evaluation of the epidemiologic evidence and physiopathological links that correlate hypertension and nocturia. Emphasis is placed on the need to take a pro-active attitude to detect and treat this hazardous condition.

Biochemical and body composition analysis of nocturia in the elderly

AIMS

Nocturia is a common symptom in the elderly, and various contributing factors have been suggested. Therefore, in order to investigate which factors are strongly related to occurrence of nocturia, we performed a suite of examinations.

METHODS

One hundred eighty volunteers were divided into three groups: a young adult control group (60 healthy persons without nocturia), an elderly control group (60 healthy persons with a low mean frequency of nocturnal urination, i.e., <once per night), and an elderly nocturia group (60 healthy persons with a high mean frequency of nocturnal urination, i.e., more than twice per night). Biochemistry tests, measurement of the osmotic pressure of plasma and urine, and body composition analysis were performed in three groups during the daytime and nighttime. In the elderly control group and the elderly nocturia group, measurement of blood pressure and recording of urinary frequency-volume charts were performed.

RESULTS

The features specific to the elderly nocturia group are as follows: (1) a decrease of the nighttime plasma melatonin level, (2) an increase of nighttime plasma catecholamine levels, (3) an increase of daytime and nighttime plasma natriuretic peptide levels, (4) an increase of blood pressure, (5) a decrease of daytime and nighttime urinary osmotic pressure, (6) an increase of total urine volume, and (7) an increase of the edema ratio before sleeping.

CONCLUSIONS

These results suggest that sleep disturbance, hypertension, and excessive fluid intake are major factors contributing to an increased frequency of nocturnal urination (>twice per night) in the elderly.

Investigation of biochemical factors related to non-bothersome nocturnal urination

We investigated the factors related to nocturnal urination that was not considered bothersome by comparing various parameters between subjects who felt nocturnal urination as bothersome and those who did not. A total of 94 persons (50 males and 44 females) were enrolled. They urinated >or= once per night. Each subject's perception of nocturnal urination was examined, and the subjects were divided into a bothersome group and a non-bothersome group. Blood biochemical data and urinary condition were compared between the two groups and various subgroups. There were 60 subjects (56 +/- 17 years old) in the non-bothersome group, and 34 subjects (57 +/- 17 years old) in the bothersome group. The serum melatonin level was significantly lower and the total score of the International Prostatic Symptom Score questionnaire (IPSS) and the quality of life (QOL) score were significantly higher in the bothersome group than in the non-bothersome group. Among 50 subjects with nocturnal urination >or= twice per night, the serum melatonin level was also significantly lower and the QOL score was significantly higher in the bothersome group than in the non-bothersome group. In conclusion, nocturnal urination might be not considered bothersome when subjects maintain sufficient levels of melatonin.

Diuretic pattern in adults with nocturnal polyuria: The possible contribution of blood pressure to the worsening of nocturnal polyuria

AIM

The present study was undertaken to investigate diuresis rate determinants of nocturnal polyuria (NP) in adults.

SUBJECTS AND METHODS

A total of 33 patients aged 50-87 years (mean: 68.6), with nocturnal urine volumes exceeding 10 mL per kg body weight based on records of a frequency-volume chart, were enrolled to evaluate the relationships between diuresis rates and related variables. Multiple regression analyses were conducted to identify diuresis rate determinants, including brain natriuretic peptide. Furthermore, a hypertonic saline infusion test was conducted to examine the arginine vasopressin (AVP) response to plasma osmotic change.

RESULTS

Nocturnal voids correlated negatively with the daytime diuresis rate (P = 0.019). Despite a similar total urine volume per kg body weight (TUV/kgBw), systolic and mean blood pressure (MBP) significantly correlated with the nocturnal diuresis rate positively and the daytime diuresis rate negatively. The MBP, which was selected as a representative variable for blood pressure, was found to be an independent determinant for the nocturnal. The MBP and TUV/kgBw were independent determinants for the daytime diuresis rate on multiple regression analyses. Neither age, AVP, nor brain natriuretic peptide were determinants for them. When divided into two groups using their median nocturnal diuresis rates (0.023 mL/kg/min), there was no difference in the prevalence of stroke and the taking of hypnotics between the groups. Overall, a hypervolemic condition or increased sympathetic nerve activity in NP was suggested using the hypertonic saline infusion test.

CONCLUSIONS

These results indicate that blood pressure might play an important role as a determinant of increasing nocturnal diuresis in NP.

Multifactorial nature of male nocturia

OBJECTIVES

To conduct a prospective study to determine the causes of nocturia in men.

METHODS

The study included 41 male patients (mean age 72.5 years) bothered by nocturia (two or more micturitions per night). Eleven asymptomatic young men (mean age 28.4 years) were enrolled as a control group. All completed a 3-day voiding diary. Daytime and nighttime urine samples were collected to determine osmolality and sodium and potassium levels. Urodynamic studies were performed for all patients with nocturia to evaluate for bladder outlet obstruction using the International Continence Society definition. Polysomnography was performed on selected patients to detect sleep apnea.

RESULTS

The average nighttime voiding frequency was 3.9 in the patients with nocturia. Nocturnal polyuria (NP) was found in 34 (82.9%) of 41 patients. In these patients, the nighttime urinary sodium excretion was significantly greater than the daytime excretion, with lower nighttime urine osmolality. In contrast, nighttime and daytime sodium excretion was not significantly different in patients without NP, and greater nighttime urine osmolality was noted in the patients without NP and the control group. Of the 41 patients, 24 (58.5%) had a small nocturnal bladder capacity, with detrusor overactivity in 14 of 24 patients. Eighteen patients (43.9%) had both NP and a small nocturnal bladder capacity. Another 18 patients had bladder outlet obstruction and NP. Two patients had sleep apnea.

CONCLUSIONS

Our observations have shown that a significant contributor to male nocturia is NP, which results from a disordered diurnal rhythm of sodium excretion and other unknown factors causing nocturnal urinary dilution. However, male nocturia can also be secondary to a combination of factors. Detailed workup is necessary to elucidate all causes.

Snoring as a cause of nocturia in men with lower urinary tract symptoms

OBJECTIVES

Snoring increases with increasing age and body mass, and repeated periods of hypoxia cause nocturnal polyuria. Accordingly, we examined the occurrence of snoring problems in patients scheduled for transurethral prostatic resection.

METHODS

Of 171 men scheduled for TUR-P, 41 were excluded due to cardiac disease, diabetes, or prostatic malignancy. Of the remaining 130 patients, 12% were troubled by snoring that disturbed their sleep. The severity of their snoring was evaluated by questionnaires, micturition charts, and determination of nocturnal capillary oxygen saturation (SaO(2)) and pulse rate. Plasma levels of cortisol, arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were measured in the morning and at 2 p.m. Fifteen non-snoring patients also scheduled for TUR-P served as controls.

RESULTS

Compared to controls, the snoring patients had a significantly higher body mass index (BMI), voided more frequently, and produced more urine at night. They also had a significantly larger number of hypoxic episodes at night, which, along with low SaO(2) levels, correlated with the nocturnal diuresis. Snorers did not differ significantly from controls in regard to excretion of cortisol and AVP, but they did have higher plasma levels of ANP.

CONCLUSIONS

We recommend that elderly obese men with urgency at night be questioned about snoring, and that micturition frequency and volume charts be completed before deciding to operate.

Relation between nocturnal voiding frequency and nocturnal urine production in older men:a population-based study

OBJECTIVES

To describe the normal values for nocturnal urine production and its determinants, as well as the relation between nocturnal urine production and voiding frequency.

METHODS

Data were collected from 1688 men aged 50 to 78 years without bladder or prostate cancer, radical prostatectomy, neurogenic bladder dysfunction, or negative advice from their general practitioner. Measurements included self-administered questionnaires, a 3-day frequency-volume chart, transrectal ultrasonography of the prostate, uroflowmetry, and postvoid residual urine volume measurement. The mean nocturnal urine production was computed from the frequency-volume charts. Linear regression analyses were performed to determine associated factors for nocturnal urine production. Areas under the receiver operating characteristic curves were used to describe the discriminative value of nocturnal urine production on nocturnal voiding frequency. A cutoff value for "increased" nocturnal urine production was defined using logistic regression analysis.

RESULTS

The nocturnal urine production was 60.6 mL/hr for the total study population; it increased with age and was significantly higher in men with 24-hour polyuria. Nocturnal urine production was on average higher in men with increased nocturnal voiding frequency, but had only a reasonable discriminative value on nocturnal voiding frequency (areas under receiver operating characteristic curve of 0.71 and 0.76). Nocturnal urine production exceeding 90 mL/hr is suggested as abnormal.

CONCLUSIONS

On average, nocturnal voiding frequency is indicative of nocturnal urine production. However, nocturnal urine production is only a modest discriminator for increased nocturnal voiding frequency. Therefore, the use of nocturnal urine production as an explanatory variable for nocturnal voiding frequency in daily practice is of little value.

Normal values and determinants of circadian urine production in older men: a population based study

PURPOSE

We evaluated circadian urine production and its determinants in a large population based sample of older men.

MATERIALS AND METHODS

We collected data on 1,688 men 50 to 78 years old, without radical prostatectomy, prostate or bladder cancer, neurogenic bladder disease or negative advice from their general practitioner, recruited from the population of Krimpen, the Netherlands. Measurements consisted of self-administered questionnaires, including the International Prostate Symptom Score, a 3-day frequency-volume chart, transrectal prostatic ultrasound, uroflowmetry and post-void residual volume. Hourly urine production was determined and urine production day-to-night ratio was calculated from the frequency-volume chart.

RESULTS

Men younger than 65 years showed a clear circadian urine production pattern, whereas in older men this pattern was less clear. Smoking, use of diuretic drugs, post-void residual and 24-hour polyuria reinforced the circadian pattern, in favor of daytime urine production. The urine production day-to-night ratio was not associated with prostate enlargement, reduced urinary flow rate, body weight, hypertension, cardiac symptoms, diabetes mellitus, use of antidepressants, cardiac or hypnotic drugs.

CONCLUSIONS

Urine production in men younger than 65 years showed a clear circadian pattern in contrast to men older than 65 years. These data can be used as a reference when describing urine production patterns in select populations. In daily practice frequency-volume charts can be used to determine urine production. This method is inexpensive, easy to use and provides valid information on urine production in a natural environment.

Efficacy of desmopressin in treatment of refractory nocturia in patients older than 65 years

OBJECTIVES

To evaluate the efficacy of desmopressin treatment in patients 65 years old and older with nocturia and to determine whether baseline urodynamic characteristics influenced the outcome of treatment.

METHODS

Patients with nocturia three or more times a night and nocturnal polyuria refractory to medication were treated with oral desmopressin 0.1 mg at bedtime for 4 weeks. Data from urodynamic studies and a voiding diary, nocturnal urine volume, urine specific gravity, serum sodium and potassium level, and quality of life index were measured at baseline, 4 weeks, and 4 weeks after discontinuation of treatment.

RESULTS

A total of 30 patients (25 men and 5 women) were enrolled in the study. The mean age was 75.4 +/- 6.6 years. Five patients (16.7%) reported side effects, including hyponatremia in one. Twenty patients (66.7%) reported a good response with both reduced nocturnal frequency (5.2 +/- 1.16 times versus 2.24 +/- 1.12 times a night, P = 0.000) and urine volume (955.6 +/- 255.9 mL versus 522.8 +/- 210.5 mL, P <0.0001). Two patients (6.7%) had improved nocturnal frequency, and 3 patients (10%) reported no effect at all. After discontinuing the medication for 4 weeks, 13 patients (52%) had improved symptoms compared with baseline and 6 (24%) remained at their post-treatment frequency of nocturia. Urodynamic studies revealed that 15 patients had detrusor instability and 17 had a cystometric capacity of 250 mL or less. No significant difference was found in the success rate relative to the urodynamic results.

CONCLUSIONS

Desmopressin is safe and effective in the treatment of severe nocturia in patients 65 years old and older.

Nocturnal polyuria in older people: pathophysiology and clinical implications

OBJECTIVES

To review the physiological changes of aging which affect the systems involved in urine formation and to consider how these changes interact with changes in bladder function, thereby leading to the onset of nocturnal polyuria with associated urinary frequency, nocturia, and incontinence. Based on this information, data are presented on the effectiveness of pharmacological interventions which reduce the rate of urine formation and, thus, can be of benefit in reducing symptoms, especially during the nighttime.

METHODS

Peer-reviewed journal articles were identified by MEDLINE Search and by review of the literature.

CONCLUSIONS

As a consequence of age-associated diminished renal concentrating capacity, diminished sodium conserving ability, loss of the circadian rhythm of antidiuretic hormone secretion, decreased secretion of renin-angiotensin-aldosterone, and increased secretion of atrial natriuretic hormone, there is an age-related alteration in the circadian rhythm of water excretion leading to increased nighttime urine production in older people. The interaction of nocturnal polyuria with age-related diminution in functional bladder volume and detrusor instability results in the symptoms of urinary frequency, nocturia and, in some persons, incontinence. The additional impact of Alzheimer's disease on these physiological and aging changes, as well as on a diminished perception of bladder fullness, leads to an even greater risk of urinary incontinence in these patients. Treatment of nocturnal polyuria with the antidiuretic hormone analog, DDAVP (desmopressin), can result in decreased nocturnal urine production with improvement in symptoms of frequency, nocturia, and incontinence.

Cross-sectional study of nocturia in both sexes: analysis of a voluntary health screening project

OBJECTIVES

To assess the prevalence of nocturia and its impact on the quality of life in both sexes by analyzing almost 2500 individuals participating in a health survey.

METHODS

During a 12-month period, we included an incontinence questionnaire, which was largely based on the Bristol female lower urinary tract symptoms questionnaire, in the voluntary health examinations in the area of Vienna. In parallel, we recorded the medical history, concurrent medical therapy, physical examination findings, sociodemographic parameters, and blood laboratory study results.

RESULTS

The data of 1247 women (age 49.8 +/- 13.5 years) and 1221 men (age 48.5 +/- 11.9 years) were analyzed. The percentage of individuals with nocturia of two or more times increased constantly with age: less than 30 years, 3.1% of women and 3.4% of men; 30 to 59 years, 7.2% of women and 5. 7% of men; and 60 years old or older, 26.7% of women and 32.4% of men. Age-adjusted extrapolation to the general population (older than 20 years) currently living in Austria yielded that 10.8% of men and 11.8% of women have nocturia of two or more times. Overall, 66. 9% of women and 62.2% of men reported a negative impact of nocturia on their quality of life. The correlation was close between the degree of nocturia with the quality-of-life impairment in both sexes. Several voiding symptoms correlated significantly (P <0.001) with nocturia.

CONCLUSIONS

Nocturia is almost equally present in both sexes, and the incidence and severity increase constantly from early adolescence to senescence. Approximately 10% of the general population (older than 20 years) have nocturia of two or more times, which impairs the quality of life in two thirds.

Relation of nocturnal polyuria of the elderly to essential hypertension

Nocturnal polyuria is common in the elderly. In this condition the normal circadian rhythm of urine production is reversed so that urine flow is higher at night than during the day. Elderly men with nocturnal polyuria are commonly referred for prostate surgery, which, not surprisingly, fails to relieve their symptoms. Compared with controls, patients with nocturnal polyuria have higher nocturnal sodium excretion but not higher nocturnal free-water clearance. Similar results have been obtained in children with nocturnal enuresis. Use of vasopressin analogues to induce water retention in elderly patients with nocturnal polyuria is illogical and potentially hazardous; nocturia can be more safely alleviated by diuretic therapy. Nocturnal polyuria in the elderly is associated with hypertension: this is consistent with studies in younger age groups that show that essential hypertension is associated with nocturia and with increased night/day ratios for sodium excretion. We propose that nocturnal polyuria and essential hypertension share some of the same pathophysiological determinants. Specifically, we suggest that a defect in the nitric-oxide pathway may lead to resetting of the pressure-natriuresis relation in the kidney, sodium retention, and compensatory nocturnal natriuresis. This suggestion is consistent with evidence that ageing and essential hypertension are both associated with defects in the nitric-oxide pathway. Our hypothesis has obvious therapeutic implications. More generally, studying the pathogenesis of nocturnal polyuria in the elderly may advance our understanding of the pathogenesis of essential hypertension.