The association between nocturia and nocturnal polyuria in clinical and epidemiological studies: a systematic review and meta-analyses.

PURPOSE: We determined the relationship between nocturia and nocturnal polyuria. MATERIALS AND METHODS: The PubMed® and Embase® databases were searched for studies written in English, German, French or Dutch with original data on adult participants in an investigation of the relationship between nocturia and nocturnal polyuria. A meta-analysis of the difference in mean nocturnal voiding frequencies between patients with and without nocturnal polyuria was conducted. Nocturnal polyuria risk was compared between participants with and without nocturia, and the resulting odds ratio was subsequently converted to relative risk with 95% CIs. RESULTS: From 511 references identified we selected 78 publications of 66 studies, 15 of which met the inclusion criteria for this study. Quality scores of studies were generally high for internal validity but low for external validity. In 7 studies (1,416 participants) we estimated a standardized mean difference of 0.59 (95% CI 0.29-0.89) for nocturnal voids between nocturnal polyuria and nonnocturnal polyuria cases. In 8 other studies (with 2,320 participants) we calculated a pooled OR of 4.99 (3.92-6.37) for nocturnal polyuria in individuals with nocturia. The corresponding RR, based on a nocturnal polyuria risk in the pooled population of 63.8%, was 1.41 (1.37-1.44). CONCLUSIONS: The association between nocturia and nocturnal polyuria is apparent and robust. However, the clinical importance of the association appears to be less obvious than previously suggested based on single studies. The observed high prevalence of nocturnal polyuria, as a result of the applied International Continence Society definition, may be responsible for this discrepancy.