Increased Rates of Excessive Daytime Sleepiness in Idiopathic Normal Pressure Hydrocephalus Identified as an Independent Feature

A new cross-sectional analysis showed that patients with idiopathic normal pressure hydrocephalus (iNPH) had significantly higher levels of excessive daytime sleepiness (EDS) compared with healthy controls, with no corresponding differences in reported sleep apnea. The findings, published in the Journal of Clinical Neuroscience, suggest EDS is common in in iNPH and may be an independent nonmotor feature of the condition.¹

In the analysis, researchers included 46 patients with iNPH and 74 age- and sex-matched healthy controls. All told, results revealed that patients with iNPH demonstrated significantly higher Epworth Sleepiness Scale (ESS) scores than controls (10.3 [± 7.1] vs 6.8 [± 5.6]; P = 0.008). Following adjustment for age and body mass index (BMI), patients with iNPH also demonstrated significantly higher ESS scores compared with the controls, corresponding to an adjusted mean difference of 3.8 points (β = − 3.83, 95% CI: 1.44–6.22, P = .002).

Additional findings observed in categorical ESS severity analyses showed a higher proportion of moderate-to-severe daytime sleepiness among patients in the iNPH group, supporting the clinical relevance of the observed group difference. In terms of apnea, authors reported no significant group difference when it was analyzed either as a categorical variable (P = .406) or as a numeric variable (median: 3.0 [IQR, 3.0] vs. 3.0 [IQR, 3.0]; P = .308), with a small effect size (rank-biserial r = .193).

"Our results suggest that while sleepiness is clearly relevant in iNPH, its relationship to apnea and treatment response remains complex. Differences in apnea assessment methodology, particularly the reliance on subjective reports rather than polysomnography in the present study, may partly account for discrepancies with prior reports,” lead author Halil Önder, MD, associate professor in the Movement Disorders Center at the Ankara Etlik City Hospital in Turkey,and colleagues wrote.¹ “The controlled design of our study further suggests that excessive daytime sleepiness in iNPH cannot be fully explained by sleep-disordered breathing or common comorbidities and may reflect a non-motor aspect of the condition that is not adequately captured by standard clinical severity scales.”

This study retrospectively analyzed clinical and sleep-related data from patients evaluated at the Movement Disorders Polyclinic of Etlik City Hospital between January 2023 and July 2024, whereas healthy controls were recruited prospectively. All patients underwent standardized neurological and radiological assessments to confirm iNPH diagnosis based on the Japanese Guidelines.² Clinical evaluations included the iNPH Grading Scale, Movement Disorder Society–Unified Parkinson’s Disease Rating Scale Part III, and the ESS.^3-5 Authors noted that apnea was assessed during a clinical interview using a semi-structured question on breathing pauses during sleep.

READ MORE: Fatigue and Objective Sleepiness Show Distinct Profiles in Patients With Obstructive Sleep Apnea

Coming into the study, the cohort comprised patients with iNPH (mean age, 69.3 [± 8.8] years) and controls (mean age, 66.7 [± 8.1] years) matched for age and sex, although patients with iNPH were slightly older (P = .026) and had a higher mean BMI (29.7 [± 4.4] kg/m² vs 28.0 [± 5.5] kg/m²; P = .037). Authors noted that comorbidities such as hypertension, diabetes, and hyperlipidemia were similar between groups. In the iNPH cohort, findings showed that 37% were classified as possible, 46% as probable, and 17% as definite disease.

Although ESS scores remained significantly higher in patients with iNPH even after adjusting for age and BMI, no significant associations were observed between ESS scores and clinical or demographic variables in the iNPH group. Researchers noted that correlation and regression analyses demonstrated that EDS was not significantly related to motor symptoms, gait impairment, cognitive status, urinary incontinence, or BMI (all, P >.05). These findings were consistent in subgroup analyses restricted to patients with probable or definite iNPH.

“Clarifying the relationship between iNPH and sleep is not only important for understanding pathophysiology but could also inform patient monitoring and therapeutic approaches. Future studies combining objective sleep assessments and neuroimaging, ideally with prospective pre- and post-shunt follow-up, will be essential,” Önder et al noted.¹ “Importantly, greater insight into the interplay between iNPH and sleep may also open avenues for adjunctive interventions, such as sleep-focused rehabilitation strategies, with potential relevance for patient care.”

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REFERENCES
1. Onder H, Erdogan N, Gunaydin A, Comoglu S. Excessive daytime sleepiness in patients with idiopathic normal pressure hydrocephalus: A controlled cross-sectional study. J Clin Neurosci. 2026;146:111885. doi:10.1016/j.jocn.2026.111885
2. Nakajima M, Yamada S, Miyajima M, et al. Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus. Neurol Med Chir (Tokyo). 2021;61(2):63-97. doi:10.2176/nmc.st.2020-0292
3. Kubo Y, Kazui H, Yoshida T, et al. Validation of grading scale for evaluating symptoms of idiopathic normal-pressure hydrocephalus. Dement Geriatr Cogn Disord. 2008;25(1):37-45. doi:10.1159/000111149
4. Postuma RB, Berg D, Stern M, et al. MDS clinical diagnostic criteria for Parkinson's disease. Mov Disord. 2015;30(12):1591-1601. doi:10.1002/mds.26424
5. Johns MW. A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep. 1991;14(6):540-545. doi:10.1093/sleep/14.6.540