Idiopathic normal-pressure hydrocephalus and obstructive sleep apnea are frequently associated: A prospective cohort study

Background: Idiopathic normal-pressure hydrocephalus (iNPH) is defined by ventriculomegaly, cognitive decline, urinary incontinence and gait problems. Vascular risk factors (VRF) are associated with iNPH but obstructive sleep apnea (OSA) a well-known independent VRF is seldom mentioned. Methods: We investigated the presence of sleep-disordered breathing in a prospective cohort of 31 consecutive unselected patients with iNPH using sleep questionnaires and nocturnal polysomnography (PSG). Results: We found OSA in 90.3% (28/31) patients with iNPH; all had undiagnosed sleep abnormalities (snoring, awakenings, nocturia) and excessive daytime sleepiness (Epworth scale = 11.4 +/- 6.4; normal < 8). Nocturnal PSG showed moderate-to-severe OSA in 25 patients (80.6%) with mean apnea-hypopnea index (AHI) 31.6 +/- 23-6/h; mean respiratory distress index (RDI) 34.5/h; and, mean SaO(2) desaturation at nadir, 82.2 +/- 7.5%. The observed OSA prevalence is statistically significant: 90.3%, 95%CI 743-97.5; p = 0.000007. Other VRF included overweight body-mass index (BMI > 25- < 30 kg/m(2)) in 59%, hyperhomocysteinemia 57%, hypertension 43%, hyperlipidemia 39%, diabetes 32%, smoking 21%, coronary disease 18%, and previous stroke 10%. Conclusion: Abnormal sleep breathing is frequently associated with iNPH. Validation in larger series is required but we suggest including sleep evaluation in patients suspected of iNPH.