OBJECTIVES: Nocturia (getting up at night to void) can have a negative impact on quality of life (QoL), but limited data are available to determine the size of this impact. This study aimed to derive utility data on the impact of nocturia on QoL from the randomised clinical trial CS29 (clinicaltrials.gov; NCT00477490) for desmopressin versus placebo. METHODS: SF-12 data collected at three time-points in CS29 (n=803, male=434, female=369) were mapped to utility values using the SF-6D. Multiple data points were available per patient; a mixed model, with patient as a random effect variable, was therefore fitted using the generalised additive mixed model procedure in R. Utilities were produced accounting for the difference in various potentially clinical significant factors: age, body mass index, gender, number of co-morbidities, number of voids (NOV) and time to first void (TTV, also called first uninterrupted sleep period - FUSP). Diagnostic plots were produced to test model fit (scatter, residual and Q-Q), and Spearman rank correlations were calculated for all pairwise comparisons to test for multicollinearity in the data. For calculation of predictive utilities, all variables were set to their median values. RESULTS: All diagnostic plots showed a good model fit and no violation of model assumptions. Though multicollinearity was found between NOV (median=3.33 voids) and TTV (median=1.78h), both variables were kept in the model to determine their relative impact on QoL. Both NOV and TTV had a significant impact on utility, with up to 0.1 change in score. The utility was 0.75, 0.72 and 0.69 for [0;2[, [2;4[ and [4;+∞[ voids per night, respectively. Age presented with the lowest utility score for patients aged 40-50. Male patients had a higher score than female patients. CONCLUSIONS: Nocturia severity has a significant impact on QoL. NOV and TTV can cause changes up to 0.1 in utility score.