Objective: To estimate the long-term risk of developing dementia in the general Parkinson’s disease (PD) population and to assess the influence of age at PD diagnosis, sex, and education on dementia risk over time.

Background: Dementia and cognitive impairment are significant concerns in PD, and understanding the future risk of dementia is important for both patients and clinicians. However, estimates of dementia risk in PD vary widely, and some research cohorts—particularly those with selected populations—report lower dementia rates than previously observed.

Method: We analysed data from the Parkinson’s Incidence Cohorts Collaboration (PICC), comprising six well-characterized European population-based, unselected cohorts of newly-diagnosed PD. This study included 878 incident PD patients recruited between 2002 and 2013, with data from up to ten years of prospective follow-up. Dementia diagnoses were made using standardized clinical criteria, and cumulative dementia incidence was estimated using the Kaplan-Meier method.

Results: Among 878 patients (mean age at PD diagnosis: 69.8 ± 9.3 years; 61% male), the estimated probability of dementia at 5 and 10 years was 24% and 50%, respectively, after accounting for censoring and death. Stratifying for age at PD diagnosis showed that the 10-year cumulative incidence of dementia was 11% in those younger than 56, significantly lower than in those aged 56–70 years (41%) and those older than 70 years (64%; p<0.001). More males were predicted to develop dementia by 10 years (54%) compared to females (45%), though this difference was not significant (p=0.19). Additionally, a higher level of education (>13 years) was associated with lower 10-year dementia incidence (44%) compared to those with lower education (<13 years; 54%; p = 0.008). Similar patterns were observed in only patients diagnosed with PD after 2008.

Conclusion: Dementia is common in the general PD population, with the 10-year cumulative incidence approaching 50%. These estimates contrast with more optimistic findings from selected clinic-based research cohorts. Given the aging population and the projected increase in older adults with PD, these findings are critical for improving patient care and informing healthcare policy.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-dementia-risk-in-the-general-parkinson-disease-population/