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Reflections on Nocturia on World Sleep Day 2017
Professor Donald L. Bliwise, PHD
Emory University School of Medicine
Atlanta, Georgia (USA)
As a long-time researcher in the field of sleep and sleep disorders but a relative newcomer to urologic research, I find that conversations with valued colleagues in both domains frequently and invariably center on a single fundamental question: do people awaken because they need to void, or do they awaken and only then appreciate the need to void? This conundrum is vexing but also highly relevant for clinicians in both specialties. After all, if helping people sleep better and awaken less frequently leads to fewer bathroom trips, that would inevitably please sleep medicine specialists and argue for one direction of causality. On the other hand, many urologists have long appreciated that nocturia itself is a treatable cause of poor sleep and may cause daytime fatigue and tiredness that reduce daytime quality of life. Elsewhere I have written about the compelling scientific evidence on both sides of this two-way street (Bliwise 2014). And indeed, most assuredly, there is evidence for both. On this World Sleep Day, I thought that I would push the existing data a bit further to see if we could derive any glimmer of which causal arrow is larger. I will base my speculations on two studies, one relatively recent, and one considerably older.
In studying a relatively large population studied longitudinally over 5 years, Araujo et al (2014) noted that both persistently poor sleep and frequent nocturia were associated with development of incident nocturia and incident poor sleep, respectively. In short, there was clear evidence for bi-directionality. But which was stronger? The adjusted OR for poor sleep causing nocturia was 1.42 and that of nocturia causing poor sleep was 1.98. Although technically only valid for extrapolation over 5 years of observation to populations of similar race, socioeconomic strata and demographics as the one studied here, if one looks at the ratio of the incremental odds for each causal direction, the ratio is indicates that, at least in within these data, individuals were about 40% more likely to awaken because of nocturia rather than vice versa. These are population-based data, subject to constraints that they can never truly extend to the level of the individual case, and furthermore, they derive from each patient’s internal calculus of what is typical, which unquestionably represents a summary of experiences of sleep and nocturia encompassing many, many nights. What about addressing this question from the standpoint of the individual case? Here I turn to a study from over 20 years ago, but one that, I believe, provides to be a most surprising answer.
Pressman et al (1996) recorded patients while they slept in a sleep lab undergoing diagnostic polysomnography. There was nothing unusual about that. However, as indispensably fascinating aspect of this older study was that each patient was asked whenever they asked to use the bathroom (in sleep labs, this is a very typical nightly occurrence that occurs for almost all patients at least once and keeps the technologist “on their toes,” lest they fall asleep during the monitoring process) why they awakened? More specifically, did the urge to void awaken them or did they awaken for another reason? In many respects, the answer to this is as close to the experiential component of nocturia as one can get. One simply asks that patient right then and there: “why are you going to the bathroom now?” The answer was revealing. About half the time, patients said they awakened because of the need to void, and about half the time the bathroom trip was prompted by other factors. Remarkably, it was nearly 50/50. In other words, to know the answer to this question, one might as well flip a coin.
What does all of this mean? What it means to me is that causality is bidirectional, not only at the epidemiologic level but also at the fundamental level of human experience. There may never be a “true” answer to this question. Is that a problem? To the extent that any clinician of any specialty treating patients for nocturia seeks to help his or her patients sleep better at night, the findings suggest to me that one must approach nocturia from several different perspectives (sleep, urologic). Both could be correct. More importantly, both might serve to benefit the patient, which is ultimately why we here at the Nocturia Resource Centre continue to dialogue about this fascinating and clearly multi-determined problem, so common for so many people when they try to sleep.
Araujo AB, Yaggi HK, Yang M, McVary KT, Fang SC, Bliwise DL. Sleep related problems and urological symptoms: testing the hypothesis of bidirectionality in a longitudinal, population based study. J Urol 2014: 191: 100-6.
Bliwise DL. Cataloging nocturia (circa 2014). Sleep 2014: 37: 631-3.
Pressman MR, Figueroa WG, Kendrick-Mohamed J, Greenspon LW, Peterson DD. Nocturia: a rarely recognized symptom of sleep apnea apnea and other occult sleep disorders. Arch Intern Med 1996; 156: 545-50.
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