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 SaO₂ desaturation at nadir, 82·2 ± 7·5%. The observed OSA prevalence is statistically significant: 90·3%, 95%CI 74·3–97·5; p = 0·000007. Other VRF included overweight body-mass index (BMI >25- < 30 kg/m²) 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.