The High Prevalence and Incidence of Normal Pressure Hydrocephalus in the United States
Objective:
To estimate the prevalence and incidence of Normal Pressure Hydrocephalus in the United States.
Background:
Normal Pressure Hydrocephalus (NPH) is a treatable cause of gait disturbance, cognitive impairment, and incontinence in older adults. We quantified the epidemiology of radiologic NPH (Evans Index [EI] > 0.30 plus callosal angle [CA] < 90°) and “possible NPH” (radiologic NPH + gait impairment) across large U.S. aging cohorts.
Design/Methods:
We analyzed 3D-T1-MRI and harmonized clinical data from four longitudinal cohorts at ages ≥ 60 years: BLSA (1,145 enrolled; 875 analyzed), BIOCARD (389;303), NACC (7,421;6,754), and ADNI (3,139;2,994), totaling 10,926 unique participants and ~25,000 eligible MRIs. Prevalence was estimated within prespecified age bands (60–69, 70–79, ≥80 yrs). Incidence was computed among participants at risk with ≥1 follow-up. Progression from radiologic to possible NPH was evaluated in cohorts with post-onset gait follow-up.
Results:
Prevalence rose steeply with age. Possible NPH increased from 0.2–0.7% at 60–69 to 1.4–2.7% at 70–79, reaching 3.9–5.4% at ≥80. Similarly, radiologic NPH showed a parallel age increase, with consistently higher age-specific rates in men. Incidence of radiologic NPH was ~5–6 per 1,000 person-years in BLSA (6.19; 95%CI, 4.14–8.89) and BIOCARD (5.06; 2.52–9.05), and ~10 per 1,000 person-years in NACC (10.09; 7.66–13.05) and ADNI (10.11; 8.05–12.54), consistent with ~0.5–1.0% new cases per decade. Incidence of possible NPH was lower and cohort-dependent, reflecting underlying age distributions: BLSA 3.23 (1.61–5.77), BIOCARD 2.41 (0.78–5.62), and NACC 11.15 (5.34–20.50) per 1,000 person-years (restricted to visits with gait data). Progression from radiologic to possible NPH was substantial when follow-up gait assessments were available. Cumulative incidence reached 0.38 (BLSA) and 0.81 (NACC) by 5 years.
Conclusions:
NPH burden increases sharply with age, radiologic criteria often precede clinical gait impairment, and progression risk is meaningful over follow-up. These data support standardized imaging and routine gait assessment to enable earlier identification and intervention.
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