HOLLYWOOD, FLA. — The nighttime void volumes of people with an overactive bladder or primary insomnia were each significantly lower than controls, in an unexpected finding from a small pilot study.
“This is the first study to evaluate sleep and bladder diaries of insomniacs, people with overactive bladders, and controls,” said Dr. Cindy L. Amundsen, a urogynecologist at Duke University in Durham, N.C.
The objective was to compare the nighttime bladder symptoms between 10 people with overactive bladder (OAB), 10 people with insomnia, and 5 control patients with neither condition.
Some patients said “they've been told for years they had an overactive bladder, but [they] acted more like insomniacs and vice versa,” she said at the annual meeting of the American Urogynecologic Society.
All participants completed 7-day sleep diaries that included the number of awakenings and the duration of sleep. They also filled out 3-day bladder diaries with timing and volume of all voids.
Dr. Amundsen and her colleagues had expected to find notably lower nighttime urinary volumes in the participants with detrusor overactivity because of a greater voiding frequency. However, they recorded lower average nighttime void volumes in both the cohort with OAB (211 mL) and with insomnia (294 mL), compared with controls (460 mL). The study was funded by grants from Astellas Pharma and GlaxoSmithKline. Dr. Amundsen and her associates reported no relevant disclosures.
The mean daytime voided volume was statistically lower in the OAB patients (171 mL), compared with the insomnia patients (246 mL) and controls (291 mL).
The OAB patients had a significantly greater number of voids in 24 hours despite comparable total urine output per day. The total mean number of voids was 11.5 in the OAB group, 6.4 in the insomnia group, and 6.1 in controls. The total number of nocturia episodes likewise was significantly higher in the OAB group at 2.9, compared with 0.4 in insomniacs and 0.3 in controls.
All participants rated their perceived urgency on a 1-5 scale in the bladder diaries. The mean degree of urgency was 2.6 in the OAB group, 1.5 in the insomnia group, and 1.6 for the controls.
There was no significant difference in age or body mass index between the groups. Eligibility criteria for the OAB cohort included 3 or more months of symptoms, eight or more voids in a typical 24 hours, and two or more nocturia episodes per night. Those in the primary insomnia group reported awakening two or more times per night.
In addition, participants with OAB tended to void more quickly after awakening at night. “Polysomnogram and cystogram information was not presented here. But insomniacs spend more time being awake before they void compared to OAB patients. They are up 6-10 minutes, [and voiding is] almost an afterthought, whereas OAB patients void within 2 minutes in general,” she said.
In related data presented as a poster at the meeting, she and her colleagues found mean total sleep time was 423 minutes for the same 10 patients in the OAB group, 295 minutes for the insomniacs, and 444 minutes for controls.
Nocturia caused all the awakenings in the OAB group. In contrast to insomniacs, the participants with OAB were able to fall back to sleep faster—the mean time awake after sleep onset was 39 minutes in this group, compared with 103 minutes in insomniacs and 14 minutes in controls. These differences were statistically significant, and confirmed the sleep-disrupting effects of nocturia in the OAB group, the researchers noted.