Association Between Change in Dental Hygiene Practices and Incidence of Dementia

AIM: To investigate whether changes in toothbrushing frequency influence the incidence of dementia. MATERIALS AND METHODS: This is a retrospective cohort study using the Korean National Health Insurance Service database. Among 91,978 adults who received two oral health screenings between 2002 and 2005, 74,156 were included after exclusions. Participants were followed until 2019. Participants were categorised into nine groups based on toothbrushing frequency (≤ 1, 2, ≥ 3 times/day) at each screening. Main outcomes such as incidence of overall dementia, Alzheimer's disease (AD) and vascular dementia (VaD) were assessed using Cox proportional hazards models, adjusting for potential confounders. RESULTS: Individuals who increased their toothbrushing frequency to ≥ 3 times/day showed reduced risks of overall dementia (aHR 0.79, 95% CI 0.64-0.99) and AD (aHR 0.76, 95% CI 0.59-0.96). Those who decreased their brushing to ≤ 1 time/day had a higher risk of AD (aHR 1.31, 95% CI 1.05-1.65). A decrease from moderate brushing frequency was associated with elevated VaD risk (aHR 1.32, 95% CI 1.02-1.70). CONCLUSION: Improvements in dental hygiene practices may lower dementia risk, even among those with poor baseline habits. Conversely, lapses in oral care among previously consistent brushers may increase dementia risk.