Palta, Priya

Introduction: Plasma biomarkers of Alzheimer’s disease (AD), including amyloid-β (Aβ42/Aβ40), phosphorylated tau (p-tau181), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) have shown strong reliability in predicting dementia risk. White matter hyperintensities (WMH) represent a major vascular contributor to dementia. We investigated how plasma biomarkers of AD interact with WMH on MRI to influence incident dementia risk. Methods: We included dementia-free participants from the Atherosclerosis Risk in Communities (ARIC) Study who underwent MRI and plasma biomarker assessment at Visit 5 (2011–2013). WMH was quantified and considered continuously (log-transformed and standardized), and in tertiles. Plasma biomarkers were log-base-2-transformed. Cox proportional hazards models were used to estimate dementia risk over 10 years associated with plasma biomarkers and WMH, independently and multiplicatively. Models were adjusted for demographic variables (age, sex, race, and education), vascular risk factors (hypertension, diabetes, smoking status, body mass index, and estimated glomerular filtration rate), and APOE ε4 status. Results: Among 1,538 participants (aged 67- 90 years, 29% Black), 30% ( N = 462) developed dementia over the 10-year follow-up period. For every doubling of plasma Aβ42/Aβ40 , indicating lower amyloid burden, dementia risk decreased, while doubling of p-tau 181 , NfL, and GFAP were each associated with increased dementia risk, in separate models; each of these associations was independent of WMH (Table 1). Additionally, dementia risk increased per SD increase in WMH, independent of each plasma biomarker. Although no multiplicative interaction terms reached statistical significance (p<0.05), there was suggestive evidence that Aβ42/Aβ40 and GFAP have smaller effect sizes on dementia risk in subgroups at the highest WMH tertile (p-interactions<0.10; see Table 2). Discussion: Plasma biomarkers and WMH independently predict dementia risk over 10 years, though there remained limited evidence of multiplicative effects. Plasma biomarkers may be less important for dementia risk in individuals who also have extensive WMH. These findings emphasize the importance of incorporating both AD-specific plasma markers as well as indicators of cerebral small vessel disease, such as WMH, into dementia risk profiling.

Background: Periodontitis is a potential modifiable factor influencing dementia risk. We examined whether improving periodontal health via regular flossing is associated with lower dementia risk. Methods: A total of 9,766 Atherosclerosis Risk in Communities (ARIC) study participants with teeth were followed from visit 4 (1996-1998) through 2021. Cox proportional hazards regression was used to estimate associations between regular dental flossing (≥1/week) and incident dementia. Covariates included age, race, gender, hypertension, diabetes, alcohol use, smoking status, obesity, physical activity, education level, income, insurance status, brushing frequency, regular dental care use and apolipoprotein E4 (APOE4) allele status . Cumulative incidence functions were estimated using death as a competing event. Results: Participants had mean age 62.6 years (SD = 5.6), 56% female, 79% white, 21% black, 63% reported regular flossing and 29.2% participants carry at least one APOE4 allele. The cumulative incidence of dementia was 52.6 % overall over 25 years. Regular flossing was independently and significantly associated with a lower hazard of developing dementia (HR = 0.90, 95% CI: 0.82–0.98, p = 0.02) after adjustment for all the covariates. In contrast, tooth brushing frequency (p=0.55) and regular dental care visit (p=0.22) were not significantly associated with dementia risk. By 25 years of follow-up, the cumulative incidence of dementia was 50% among flossers compared with 57% among non-flossers (Gray’s test p<0.0001, Figure). This translated to an Absolute Risk Reduction of 7%, Relative Risk Reduction of 12%, Number Needed to Floss 14. Conclusion: Flossing, but not tooth brushing or regular dental care, is independently associated with a reduced hazard of incident dementia. Dental flossing may be an additional strategy to reduce dementia risk. For every 14 individuals who floss ≥1/week, one fewer person will develop dementia.