Objective:

To determine how environmental exposures prior to development of Parkinson’s disease (PD) relate to symptom progression in early disease.

Background:

The variability of symptom progression in people with PD (PwPD) is still largely unexplained. Specific environmental exposures have been associated with risk of PD and may predispose people to faster progression once disease develops.

Design/Methods:

PwPD in Fox Insight (FI) – an online, longitudinal study – reported various environmental exposures on the PD Risk Factor Questionnaire. We examined occupational pesticide exposure prior to PD diagnosis and head injury >5 years prior to PD diagnosis (HI). Severe HI was defined as HI complicated by fracture, seizure, or loss of consciousness. We limited analysis to PwPD who enrolled within two years of PD diagnosis and answered questionnaires at enrollment, 12 (±3) months, and 24 (±3) months.   We used Cox proportional hazard models to compare time from diagnosis to development of (a) the need for assistance with walking (according to the MDS-UPDRS II) and (b) self-reported cognitive impairment (a score of <49 on the Penn Daily Activities Questionnaire [PDAQ]) between PwPD with and without exposure, adjusting for enrollment age, sex, and education (for PDAQ). Data were censored at 27 months of follow up.

Results:

521 of 2,600 (20%) PwPD reported pesticide exposure before PD diagnosis.  1,065 of 3,278 (32%) reported HI >5 years before PD diagnosis. Pesticide exposure predicted faster progression to balance problems (aHR:2.29, 1.09–4.83, p=0.029) and to cognitive impairment (aHR:1.89, 1.05–3.41, p=0.034). Severe HI predicted faster progression to cognitive problems (aHR:1.93, 1.04–3.61, p=0.038). Exposure to both pesticides and HI was associated with faster progression of cognitive problems than either alone (aHR:2.57, 1.05-6.31, p=0.039).

Conclusions:

Occupational pesticide exposure or HI prior to PD diagnosis may cause a faster progression of motor and cognitive symptoms once PD develops.