Validity and reliability of a questionnaire for evaluating nocturia, nocturnal enuresis and sleep-interruptions in an elderly population

OBJECTIVES: To validate a new questionnaire evaluating nocturia, nocturnal enuresis and sleep-interruptions in an elderly population of men and women in Denmark.

METHODS: The Nocturia, Nocturnal Enuresis and Sleep-interruption Questionnaire (NNES-Q) emerged from review of the literature and expert consensus. The questionnaire was a subset of a larger questionnaire comprising several domains on health status and voiding. Convergent and discriminatory validity was assessed in an unselected population of 2000 men and 2000 women 60-80 years old. To test reproducibility, 400 respondents were mailed a separate questionnaire 2 weeks apart. A subgroup of men and women with and without nocturia was used for evaluating reliability of number of nocturia episodes.

RESULTS: A total of 2825 (70.6%) filled in the questionnaire. A decrease in health status was correlated with increasing bother (range: -0.25 to -0.36, p<0.001, Spearman's r). These findings indicate acceptable convergent validity. Significant discriminatory validity was proven in separate groups of symptom severity (p<0.0001, Kruskal-Wallis test). Median kappa was 0.70 (range 0.58-0.86) indicating substantial agreement in the retest analysis. Number of nocturia episodes in questionnaires correlated with frequency volume charts (Spearman's rho 0.88; p<0.001).

CONCLUSION: These data support that the NNES-Q has a good discriminatory and convergent validity, and is reliable over time. The NNES-Q may be useful in epidemiological studies and may also have a potential in daily clinical work up in patients with nocturia and nocturnal enuresis.