40-Year Incidence of Early-Onset Parkinson's Disease in Southeast Minnesota

Background: Parkinson's disease (PD) most commonly surfaces at middle age. An earlier onset is named early-onset Parkinson's disease (EOPD), but the exact definition is a matter of ongoing scientific debate. Objective: To investigate 40-year EOPD incidence trends in a population-based cohort of parkinsonism in Olmsted County, Minnesota. Methods: We used the Rochester Epidemiology Project (REP) to identify all incident EOPD cases in Olmsted County, 1976-2015. A movement-disorder specialist reviewed all cases to confirm the EOPD diagnosis. For EOPD definition, we used two age cut-offs: motor-symptom onset at or before 50 and 55 years. Results: EOPD incidence was 1.43/100,000 person-years for <= 55 and 0.55/100,000 for <= 50 years. Men had a higher incidence in both groups [1.84 vs. 1.03 (p = 0.04); and 0.70 vs. 0.40 (p = 0.24), respectively]. EOPD incidence of patients with motor-symptom onset before age 55 increased from 1.02/100.000 person-year 1976-1985, to 1.32/100.000 person-year 2006-2015. A similar trend was observed when <= 50 years cut-off was used (0.28/100,000 person-years 1976-1985, to 0.59/100,000 person-year 2006-2015). However, negative binomial regression found no significant change in incidence per 10 years (RR = 1.04 and 1.24 in the two groups). Incidence was consistently higher in men than women. Median time from EOPD-symptom onset to death was shorter in the EOPD <= 55 group (21.9 years) compared to the EOPD <= 50 group (25.6 years). Conclusion: We observed an increased trend in the incidence of EOPD with both cut-off ages. Overall, incidence of EOPD was 1.43 (<= 55) and 0.55 (<= 50) cases per 100,000 person-years, higher in men.