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#342/#337 - Factors to overestimate nocturia: compartive study between data from questionnaire and frequency-volume charts

K. Muraoka, M. Honda, S. Hirano, Kawamoto, S. Shimizu, T. Panagiota, K. Hikita, M. Saito, T. Sejima, A. Takenaka

Natural history of nocturia among japanese men and women during the 5-year period from 2003 to 2007

Y. Aoki, S. Yokoi, M. Okada, Y. Matsuta, C. Matusmoto, Y. Kusaka, O. Yokoyama

By Donald Bliwise

These two studies were unrelated and initially look very different from each other, but I group them together because of their relevance for descriptive assessment of nocturia. The first (#337) is a rare longitudinal study of the natural history of nocturia in a large, unselected Japanese population that was assessed yearly over a period of 5 years. The second (#342) was a study comparing IPSS estimates of nocturnal voiding to frequency volume charts. The basic finding of the first study was that nocturia was remarkably inconsistent over the 5 years of study. Only 2.6% of the population reported nocturia at every time of measurement, whereas 71.6 % of the population reported never experiencing nocturia over the 5 years (Recall that these were population-based data not specifically derived from a nocturia population per se.) The remainder of the cases (nearly 25% of the population) “drifted” in and out of reporting nocturia. The basic finding of the 2nd study was that the IPSS overestimated scores on the FVC, and the authors made the point that detailed recording via FVC would be much preferred over a single-administration of the IPSS.

Commentary: In my mind, these two studies, though very different in scope, population and intent, converge on a very important issue in nocturia research, i.e., how much data are required to accurately describe an individual’s characteristic level of nocturia? To rephrase this, is it ever possible to merely ask someone a single question regarding how often that they void at night and expect that answer to be a realistic appraisal of what typically occurs? Muraoka et al implies that a 3 day FVC diary is sufficient, but is it really? In the Aoki et al study patients were asked only to estimate their frequency of voiding “recently” but were not given any other time referent on which to base their judgments. Might that level of imprecision (as Muraoka et al imply) be sufficient to create such an unreliable and less valid pattern of responses to a question about nocturia? My own perspective on this comes from an entirely different orientation, i.e., as someone who has conducted sleep research for many years. Sleep researchers use sleep diaries very frequently (unfortunately, seldom asking about nocturia). But holding aside for the moment that major faux pax, what can we learn from sleep diaries kept by those involved in sleep research? Sleep researchers typically insist on a week (7 nights) of diaries and frequently contend that 2 weeks (14 nights) are required to obtain any assessment of stability of an individual’s sleep patterns. If we extrapolate from that to nocturnal voiding, it would follow that even the 3-day FVC is unlikely to provide a “stable” estimate of nocturnal voiding frequency. Perhaps diaries covering a larger number of nights will ultimately be required to appreciate the variability in voiding from night-to-night. This inherent variability in the phenomenon of interest might well explain the valuable and important natural history study of Aoki et al on 8,265 individuals. Nocturia on a given night (or even 3 consecutive nights) may not necessarily be an adequate representation of characteristic tendencies for nighttime voiding. In order to understand the natural history of the phenomenon, more precise and valid rendering of the status at any given time point should probably be pursued.