The International Continence Society defines nocturia as “the number of times an individual passes urine during their main sleep period, from the time they have fallen asleep up to the intention to rise from that period [1].[2].” Several large surveys around the world report that many patients have nocturia; for example, in a survey of more than 100,000 people in the UK [3], about 60% and 20% urinated more than once and more than twice a night, respectively. In the USA, 31% and 14% urinated more than once and more than twice a night, respectively[4]. Nocturia is a major health problem and is positively associated with age [5]. A survey by the Japan Urology Association of men and women aged 40 years and older reported that 70% of the population urinated at least once during the night, with an estimated 42 million people in Japan as a whole [6]. Nocturia by itself is associated with physical distress, daytime fatigue, and decreased quality of life [7].[8]. Additionally, it is correlated with a wide variety of organic diseases and psychiatric disorders[9].[10].[11].[12] as well as an increased risk of falls and hip fractures in older adults[13].[14]. It is also associated with an increased risk of all-cause morbidity and mortality[15].[16].[17].
Thus, nocturia, prevalent in numerous individuals, particularly among older adults, encompasses a broad spectrum of causes, ranging from diminished quality of life to heightened mortality risk. However, its primary causes are identified as follows: nocturnal polyuria, reduced functional bladder capacity, and sleep disorders. While there are already some drugs for nocturnal polyuria and decreased functional bladder capacity as a result of overactive bladder, benign prostatic hyperplasia, or other factors, pharmacological agents generally have many harmful side effects in older adults. For instance, desmopressin, a medication often prescribed for addressing nocturnal polyuria, can potentially worsen heart failure, a condition prevalent in older adults, and may lead to severe hyponatremia.[18]. Anticholinergic drugs used to treat overactive bladder are strongly associated with cognitive decline[19].[20], and β3 agonists cannot be used in the presence of heart disease and arrhythmias, which are also common in older adults. Alpha1-blockers, used to treat benign prostatic hyperplasia, can induce hypotension [21], which may limit their use in this population.
Of the three major causes of nocturia, sleep disturbance has a bidirectional relationship with nocturia [22]. Epidemiological studies have consistently shown that nocturia is the predominant cause of sleep disturbances across all age demographics, with its prevalence escalating with advancing age [7].[9].[23]. However, there are limited reports suggesting that treating sleep disorders can lead to improvements in nocturnal polyuria. For example, the use of ramelteon, a sleep-inducing medication, has shown promise in enhancing nocturnal polyuria [24]. Additionally, in patients with obstructive sleep apnoea syndrome, the introduction of continuous positive airway pressure has been associated with improvements in nocturnal polyuria [25].[26]. In contrast, the widespread use of sleep-inducing drugs in older adults can pose risks, including an increased susceptibility to nighttime falls, fractures, and cognitive impairment [27].[28]. The average age of patients with nocturnal polyuria accompanying obstructive sleep apnoea syndrome is around 50 years, which is relatively lower than the broader population affected by nocturia. Consequently, its impact may be somewhat limited, particularly in older patients [25].[26].[29].
Tyagi et al. conducted noteworthy research indicating that behavioural bedtime therapy led to enhanced sleep quality and yielded a significant improvement in managing nocturnal polyuria [30]. They instructed participants to undertake four simple behavioural treatments, half of which focused on bedtime schedules. Several studies have revealed that age-related changes in sleep depth and circadian rhythm amplitude may contribute to nocturia [31]. A common feature of aging is the tendency to adopt an earlier bedtime [32], often earlier than desired [33]. As a result, older adults sleep for a longer period, become shallow sleepers, and are easily awakened by a slight urge to urinate, resulting in a longer mid-wake duration, i.e., the total amount of sleep time increases, but sleep quality deteriorates. For conditions such as advanced sleep-wake phase disorder, chronotherapy [34], in which sleep scheduling and phototherapy [35] are inherent, is considered effective, but there is no clinical research to support this [36]. We hypothesized that adjusting bedtime improves nocturia in older adults. In this study, using data from a wearable device that measures sleep-wake activity, we examined whether going to bed at an appropriate personalized time and regular sleeping habits improved nocturia.