BACKGROUND AND OBJECTIVES: The prevalence of Parkinson disease (PD), multiple sclerosis (MS), and motor neuron diseases (MNDs) is rising globally. However, it is unclear to what degree this is related to an increase in incidence or to improved survival after diagnosis. METHODS: We performed 2 nationwide, population-based, retrospective cohort studies, including all individuals living in Sweden between 2001 and 2016 and living in France between 2009 and 2022, respectively. Pooled mixed-effects regression models, with country as a random effect, were used to determine temporal trends in prevalence, crude and age-standardized and sex-standardized incidence, and age and life expectancy at diagnosis. RESULTS: = 0.01). DISCUSSION: These findings indicate that the rising MS prevalence is largely survival-driven and the rising MND prevalence reflects a true increase in incidence, whereas PD prevalence grows modestly, largely independent of incidence. Depending on the mechanism that drives prevalence, whether increased incidence reflecting changing risk factor exposures, improved survival due to therapeutic advances, or demographic aging of the population, inferences about underlying causes differ substantially between PD, MS, and MNDs, with direct implications for health care planning and etiologic research.
Guinebretiere et al. (Fri,) studied this question.