Majority of nocturia patients have nocturnal polyuria

"Clinicians should be aware that patients with nocturia are likely to have nocturnal polyuria, either alone or in combination with other factors," said study author Jeffrey P. Weiss, MD, professor of urology at State University of New York Downstate Medical School, Brooklyn.

About 50% of adults experience nocturia, and up to one-fourth void at least twice per night, he said. Nocturia is not well understood in clinical practice; it is frequently misclassified or misdiagnosed, or its cause is only partly identified. Bladder storage problems are the most well-known factors underlying nocturia, but nocturnal polyuria is probably the most prevalent.

Patients with BPH and/or overactive bladder were included in the study if the conditions had been diagnosed and treated satisfactorily.

Among the 1,412 patients screened for inclusion in the study, nocturnal polyuria was found in a minimum of 819 (58%); 478 patients did not complete a 3-day voiding diary and therefore data on nocturnal polyuria were not available. (These patients were assumed not to have nocturnal polyuria to arrive at the 58% minimum.) Of the 934 patients who completed the voiding diary, nocturnal polyuria was found in 87.7%.

Prevalence increases with age

Of the 799 patients who were randomized into the study, slightly more than one-fourth had received a diagnosis of BPH or OAB. The rate of nocturnal polyuria in the intent-to-treat subjects was 90.1%, with an increasing prevalence with age. In those 65 years or older, the rate of nocturnal polyuria was 93.9%; in those younger than 65, it was 86.5%. The mean age of patients with nocturnal polyuria was 62.6 years, compared to 56.1 years in those without nocturnal polyuria.

Some 13.1% of those with nocturnal polyuria were on concomitant urologic medications, including antispasmodics, compared to 1.7% of the study subjects who did not have nocturnal polyuria.

"Therapy for nocturia should be selected according to the cause, including nocturnal polyuria, if present, and the use of a voiding diary is crucial for identification and stratification of those causes of nocturia," Dr. Weiss advised.

Although a substantial proportion of patients screened for inclusion into the study did not complete a voiding diary, "I don't think it would be appropriate to rely on a single diary when it was certainly possible in a large cohort to get 3-day diaries," he said.