Why Does the Health-Related Quality of Life in Idiopathic Normal-Pressure Hydrocephalus Fail to Improve Despite the Favorable Clinical Outcome?

Objective: Occasionally, a favorable clinical disease-specific outcome does not reflect into improved generic health-related quality of life (HRQoL) in patients with idiopathic normal-pressure hydrocephalus (iNPH) at 1 year after the installation of a cerebrospinal fluid shunt. Our aim was to identify factors causing this discrepancy.

Methods: The 1-year HRQoL outcomes of 141 patients with iNPH were evaluated with the generic 15D instrument, in which the minimum clinically important change/difference on the 0-1 scale has been estimated to be ±0.015. A 12-point iNPH grading scale (iNPHGS) was used as a clinical disease-specific outcome measure, in which a 1-point decrease is considered to be clinically important. We identified 29 (21%) patients with iNPH from our prospective study whose HRQoL deteriorated or remained the same despite of a favorable iNPHGS outcome. We analyzed this discrepancy using patients' clinical variables and characteristics.

Results: Multivariate binary logistic regression analysis indicated that a greater (worse) iNPHGS score at baseline (adjusted odds ratio [OR], 1.7; 95% confidence interval [CI] 1.3-2.3; P < 0.001), comorbid chronic pulmonary disease (40% vs. 20%; adjusted OR 17.8; 95% CI 3.6-89.9; P < 0.001), and any comorbid nonmetastatic tumor (62% vs. 17%; adjusted OR 11.5; 95% CI 1.5-85.3; P = 0.017) predicted discrepancy between iNPHGS and 15D outcomes.

Conclusions: Frail patients suffering from certain pre-existing comorbidities may not experience improvement in generic HRQoL despite of a favorable clinical disease-specific response. Acknowledging the comorbidity burden of the patient may help clinicians and the patients to understand the conflict between patient-reported and clinical outcomes.