Occurrence of nocturia is not mediated by nocturnal hypoxia length and severity in patients with sleep-disordered breathing

Background: Nocturia is highly prevalent in subjects with respiratory sleep disturbances (ie obstructive sleep apnea). The aim of our study is to evaluate whether nocturia is associated with intermittent desaturations or hypoxia length and severity in people undergoing polysomnography.

Methods: We recruited 275 consecutive subjects attending the outpatient clinic for respiratory diseases at Campus Bio-Medico Teaching Hospital. Nocturia was defined as a self-reported voiding frequency ≥ two per night. The groups with and without nocturia were compared with parametric and non-parametric tests, as appropriated. Multivariable logistic regression analysis was used to assess the association of nocturia with patients' characteristics, including oxygen desaturation index (ODI), respiratory efforts (RE) and oxygen saturation below 90% (TST₉₀).

Results: Sixty-six (24%) subjects reported nocturia, the median ODI was 15 (8-31), the median RE was 22 (12-38) and the median TST₉₀ was 4.7 (0.3-20.6). ODI and RE were significantly higher in subjects with nocturia as compared with controls. In the multivariable model, ODI was associated with an increased probability of nocturia (OR = 1.03; 95% CI = 1.01-1.06), and the higher the ODI score, the higher the probability to have nocturia (P for trend = 0.038). No significant association was found between TST₉₀ and the occurrence of nocturia.

Conclusions: Intermittent desaturations and not hypoxia length and severity, expressed by TST₉₀, are associated with the occurrence of nocturia in subjects complaining sleep disturbances.