Incidence and survival rates of frontotemporal lobar degeneration : population-based registry study

Abstract

Background and Objectives - Frontotemporal lobar degeneration (FTLD) can present as a behavioral or language variant (bvFTLD or a primary progressive aphasia [PPA], or as a syndrome with parkinsonism, such as corticobasal syndrome [CBS] or progressive supranuclear palsy [PSP]). The incidence of FTLD varies in epidemiologic studies, reaching 3 per 100,000 person-years. Only few data exist regarding survival times. We evaluated incidence and survival rates in a population-based registry with high coverage in Southern Germany. - Methods - The epidemiologic ALS-FTLD registry Swabia covers a population of 8.4 million inhabitants in south-west Germany. Raw and age-standardized incidence rates, as well as incidence rate ratios (IRR) with 95% CIs were calculated. Median survival time was estimated for different FTLD variants using the Kaplan-Meier method. - Results - Between 2015 and 2022, 515 patients with FTLD (mean age at diagnosis 68.0 ± 9.5 years, 59.8% men) were registered. The median diagnostic delay was 24.8 months. The most common variant was bvFTLD (n = 185, 35.9%; 66.5% men), followed by PPA (n = 147, 28.5%; 51.0% men), PSP (n = 133, 25.8%; 62.9% men), and CBS (n = 22, 4.3%; 50% men). The overall FTLD incidence was 0.77 (95% CI 0.71-0.84), and the age-standardized incidence was 0.76 (95% CI 0.69-0.82) per 100.000 person-years. The age-standardized incidence was higher in men than in women, with an IRR of 1.73 (95% CI 1.44-2.00). In men, incidence increased from the age 50 years, primarily due to bvFTD, whereas in women this rise was primarily due to PSP. The median survival (N = 392) from diagnosis was 53.6 months (95% CI 50.9-62.0) overall, 73.1 months (95% CI 63.6-82.8) for patients with PPA, 42.8 months (95% CI 35.1-64.3) for patients with bvFTD, and 49.5 months (95% CI 39.2-53.7) for patients with PPS/CBS. - Discussion - We observed a raw incidence rate of 0.77, thus considerably lower than in most previous reports. Incidence was substantially higher in men than in women. The prognosis from the time of diagnosis depended highly on the specific FTLD subtype. Our data are based on the large sample size and high capture rate of a central European population-based registry.