Is the Latency from Progressive Supranuclear Palsy Onset to Diagnosis Improving?

Background: Progressive supranuclear palsy (PSP) is a neuropathologically defined disease with a broad clinical spectrum. It can initially be mistaken for other neurodegenerative diseases. Diagnosis of PSP earlier in the course may reduce its psychological and financial burden, permit earlier access to neuroprotective interventions, and avoid unnecessary diagnostic and therapeutic measures. Our impression is that physicians are more aware of PSP in the 2010s than in the 1990s. This study tests that hypothesis using the latency from symptom onset to PSP diagnosis as a surrogate outcome. Methods: We reviewed records of 385 patients with "possible" or "probable" PSP from 1990 to 2016 at the Movement Disorders Center, Rutgers Robert Wood Johnson Medical School. The time from symptom onset to diagnosis was calculated for each patient and labeled as latency. We used the Pearson correlation coefficient, Student's t-test, and ANOVA as appropriate. Results: Our data show that the mean latency (SD) from symptom onset to diagnosis PSP, in months, was 43.76 (25.60) in the 1990s, 40.76 (28.73) in the 2000s, and 29.15 (16.80) in the 2010s (P < .001). There was also an inverse relationship between age at onset and latency (Pearson's r = -0.23, P < .001). This relationship did not affect the statistical significance of our main observation. Conclusion: Our finding suggests that there is a progressive reduction in the latency over the past three decades. It may reflect increased awareness of PSP by physicians in our referral area.