Hypothesis / aims of study
Hospital stays are characterised by sleep deprivation and an altered sleeping pattern due to environmental and bio-cognitive factors. . We hypothesized that these factors might lead to higher rates of nocturnal voiding and nocturia in hospitalised patients. Nightly voiding in hospitals has been linked to an increased risk of falling: in a Belgian study, 28% of all hospital falls were related to nocturnal voiding. 
Although the prevalence of nocturia in the general population has been studied, research concerning the incidence of nocturia in hospitals is currently lacking. The aim of this study is to gain an understanding of the prevalence and incidence of nocturia in a hospital setting in older patients and to explore several possible predictors of the number of episodes of nocturia during a hospital stay.
Study design, materials and methods
A prospective, cross-sectional design was used. Patients were recruited on 5 nursing wards via convenience sampling from november 2018 till february 2019. Inclusion criteria were ≥ 65 years old, planned hospital stay. Exclusion criteria were being incontinent for urine and faeces, constant surveillance of vital parameters, former or current radiotherapy of the lower abdomen, antecedents of dementie. Patients were interviewed between the third and fifth day of admission to the hospital using a directed interview.
Collected variables were age, sex, sleeping pattern and quality, nocturia at home and at the hospital, fluid intake, snoring, restless legs syndrome, using a single or a double room, being able to close the door at night, independency for toileting, use of caffeinated drinks 4 hours or less before going to sleep, medication and intravenous fluid perfusion.
Statistical analysis was performed using SPSS 24. A negative binomial regression model, corrected per ward, was used. Outcome measure was the reported number of episodes of nocturia during the last night in the hospital, corrected for sleeping time. To calculate differences between the rate of nocturia at home versus at the hospital, a Wilcoxon signed rank test was used. P-values were two-sided and considered statistically significant at a value of <.05.
The local ethics committee approved the study protocol.
One hundred sixty-four patients fit the inclusion criteria of this study. Five patients chose not to be included in the study, 17 patients were excluded due to illness, receiving bad news or communicative problems. In total 142 patients were included. Demographics, patient and environmental characteristics can be found in table 1.
There was no significant difference in the mean number of episodes at home (1.6 voids/night, +/-1.9) versus at the hospital (1.7 voids/night, +/-1.5). Average number of voids at home during the last month, number of voids during the previous day, oral fluid intake during the previous day and lormetazepam use were significant predictors of the number of episodes of nocturia at the hospital (table 2).
Interpretation of results
Contrary to our initial hypothesis, there was no increase in the number of episodes of nocturia in the hospital versus at home. The collected data has been based on self-reported rate of nocturia: recall bias might influence these results. Further research, using objective measures of nocturia during a longer period, might improve the validity of these results.
A reduction of fluid intake is often advised as a tool to manage nocturia. In this study, oral fluid intake was an important predictor of number of episodes of nocturia. However, intravenous fluid perfusion and total fluid intake were no significant predictors of the rate of nocturia. Reproducing these results in other settings might provide a clearer view on the influence of fluid intake on nocturia.
The use of lormetazepam, a short-acting benzodiazepine, decreased the odds of an additional episode of nocturia. However, only 7 patients in this study received lormetazepam. A larger sample is needed to solidify these results.
Although other variables (sleeping quality, single versus double room, being able to close the door at night, etc.) might have an influence on the general quality of life during a hospital stay, they were no significant predictors of the rate of nocturia in the hospital.