Diagnosed oral cavity and salivary gland disorders and the risk of incident Parkinson disease, Alzheimer disease, dementia and all‐cause mortality: a retrospective cohort study

Background Oral diseases encompass a heterogeneous group of conditions affecting the oral cavity and associated structures. Certain chronic inflammatory oral diseases, particularly periodontitis, have been linked to systemic inflammation and may contribute to neurodegenerative processes. However, long‐term evidence on their association with Parkinson's disease (PD), Alzheimer's disease (AD), dementia and mortality remains inconsistent. This study aims to investigate whether diagnosed oral cavity and salivary gland disorders are associated with long‑term risk of PD, AD, dementia and all‐cause mortality in older adults. Aims To investigate whether diagnosed oral cavity and salivary gland disorders are associated with long‐term risk of Parkinson disease, Alzheimer disease, dementia, and all‐cause mortality in older adults. Methods This retrospective propensity score‐matched cohort study utilised the TriNetX US Collaborative Network. Patients aged ≥60 years with a documented diagnosis of diseases of the oral cavity and salivary glands (ICD‐10‐CM K00–K14) were 1:1 matched with patients without oral diseases on demographics, comorbidities and medication use ( n = 232 809 per group after matching). The index date was the first documented oral disease diagnosis (exposure cohort) or equivalent healthcare encounter (control cohort). New‐onset PD, AD, any‐type dementia and all‐cause mortality were assessed at 5‐ and 13‐year follow‐up using risk ratios (RRs), hazard ratios (HRs) and Kaplan–Meier survival analysis. Results At 5 years, diagnosis of oral cavity and salivary gland diseases was associated with significantly increased risk of new‐onset PD (HR 1.212, 95% confidence interval (CI) 1.133–1.296), any dementia (HR 1.132, 95% CI 1.098–1.167) and all‐cause mortality (HR 1.117, 95% CI 1.101–1.134). AD risk was modestly elevated (HR 1.100, 95% CI 1.033–1.171). At 13 years, the increased risk persisted for PD (HR 1.146), dementia (HR 1.060) and mortality (HR 1.113), but the association with AD was no longer significant (HR 0.998, 95% CI 0.959–1.038). Conclusions Diagnosed oral cavity and salivary gland diseases are independently associated with sustained long‐term risk of PD, dementia and all‐cause mortality, but the association with AD appears time‐limited. These findings highlight oral health as a potentially modifiable factor in neurodegenerative disease prevention and support multidisciplinary approaches to oral care in older adults.