Association between instrumental activities of daily living and incidence of Parkinson's disease: a nationwide population-based cohort study.

Several studies have investigated the prodromal factors for early diagnosis of Parkinson's disease (PD). Instrumental activities of daily living (IADL) involve both motor and non-motor functions, and has been used as a screening tool for dementia. This study aimed to examine the association between IADL dependency and PD incidence and identify specific IADL items linked to an increased likelihood of developing PD. This population-based cohort study used data from the Korean National Health Insurance Service database, that contains information on long-term care services. Individuals who underwent at least one health screening and completed the geriatric assessment sheet between 2009 and 2021 were included in this study. Information on IADL was extracted from the geriatric assessment sheet. The Fine-Gray subdistribution hazard model was used to assess the association between IADL dependency and PD incidence. During a mean follow-up period of 3.78 ± 3.34 years, 308 of the 21,662 participants developed PD. The highest IADL dependency was significantly associated with an increased incidence of PD (adjusted hazard ratio [aHR] = 1.458, 95% confidence interval [CI] 1.037-2.050), particularly among women or ≥75 years. Among the 10 IADL items, dependency in financial management (aHR 1.420, 95% CI 1.057-1.909, p = 0.0201) or telephone use was significantly associated with an increased incidence of PD (aHR 1.536, 95% CI 1.204-1.961, p = 0.0006). Our results suggests that IADL dependency is a potential prodromal indicator of PD. Further research on other ethnicities that considers sociocultural differences is required to confirm this association.