Parkinson's disease phenotype based on age at onset in Latin American patients: a paired-based analysis

Studies have demonstrated a higher motor and non-motor burden in Parkinson's disease (PD) patients with old age at onset compared to those with middle age at onset. We decided to test these findings in a Latin American PD population. We recruited 24 PD patients with age at onset > 65 years, and each patient was matched to 1 control patient with disease onset at ages between 48 and 60 years, matched for gender and disease duration (±2 years). Clinical test batteries that assessed motor (MDS-UPDRS), non-motor (NMSS), cognitive (MoCA), and quality of life (PDQ-8) were recorded. Groups were compared with conditional logistic regression analysis. A comparative post-hoc analysis was also conducted, considering only patients with age at onset > 70 years (n = 11) and their matched controls. Mean age at onset was 70.53 ± 3.28 and 53.79 ± 4.96 for the old-age and middle-age group, respectively. No significant differences were observed in most clinical batteries when comparing PD patients based on age at onset, with worse scores in MDS-UPDRS Part III and Tremor subscore in the middle-age onset group. The post-hoc analysis showed similar results, with non-significantly worse scores in the middle-age onset group. This is the first study reporting a more benign motor phenotype in old-age onset PD patients. Despite the lower cut-off value used for old age onset PD, vascular, epidemiological, ethnic and treatment adherence features must be also considered as potential explicative factors, with further multicenter studies in larger populations needed.