Wong, Dean F.

Background: Midlife vascular risk factors (MVRF) are associated with incident dementia. Similarly, amyloid β(Aβ) and neurodegeneration (e.g.brain volumes), as parts of the Alzheimer’s Disease (AD) ATN framework, are associated with cognition. Whether vascular and AD-associated factors contribute to dementia independently or interact synergistically to reduce cognitive ability is not well understood. Methods: Recruited from 3 U.S. communities, ARIC-PET participants were followed from 1987-89 (45-64 yo) through 2016-17 (74-94 yo). Cognition was evaluated in 2011-13 (ages 69-88), and twice more, every 2-3 years. In 2011-13, nondemented ARIC-PET participants had a brain MRI, with measurement of white matter hyperintensities (WMH) and brain volumes, with florbetapir (Aβ) PET scans in 2012-14; global cortical standardized uptake value ratio (SUVR) was log-transformed and standardized. Dementia was classified by expert review, as well as phone and medical record surveillance. The relative contributions of vascular risk (MVRF, WMH volume) and AD pathology (elevated Aβ SUVR, smaller AD signature region volumes) to incident dementia were evaluated with Cox proportional hazards regression. Results: In 298 individuals, 36 developed dementia. In models with key MVRF, demographics, and Aβ SUVR, hypertension and Aβ each independently predicted dementia risk (per SD of Aβ SUVR: HR 2.57, 95% CI 1.72-3.84; hypertension: HR 2.57, 95% CI 1.16-5.67), but didn’t interact on dementia risk. WMH (per SD: HR 1.51, 95% CI 1.03-2.20) and Aβ SUVR (per SD: HR 2.52, 95% CI 1.83-3.47) each contributed to incident dementia but WMH lost significance when MVRF were added to the model. Smaller AD signature regions were associated with incident dementia, independent of Aβ SUVR, and remained significant after adjustment for MVRF (HR per SD 2.18, 95% CI 1.18-4.01). Conclusions: Midlife hypertension and late-life Aβ independently contribute to dementia risk, but don’t synergize on a multiplicative scale. Neurodegeneration (e.g.smaller AD signature region volume) is also associated with incident dementia, independent of Aβ and MVRF. Multiple pathways leading to dementia should be considered when evaluating risk factors and interventions to reduce the burden of dementia.

Background: Periodontal disease (PD) is associated positively with neurocognitive outcomes. Few studies have investigated the relationship between PD and indicators of brain aging and vascular changes. Hypothesis: PD is associated with greater cerebral small vessel disease, lower total and regional brain volumes and elevated β-amyloid (Aβ) deposition. Methods: We included 6,793 participants who received full-mouth periodontal examinations and tooth counts at Visit 4 (1996-1998) of the Atherosclerosis Risk in Communities Study. We used a modified 3-level version of the Periodontal Profile Class to categorize PD based on severity and extent of gingival inflammation and tissue loss. Among participants who attended Visit 5 (2011-2013), n=1,306 received a brain MRI and n=248 received a PET scan. Total brain volume, Alzheimer’s disease signature volume, and presence of microhemorrhages and cerebral infarctions were ascertained via 3T MRI; Aβ deposition was assessed from PET. We regressed brain volumes on baseline PD status using weighted multivariable linear regression. Presence of cerebrovascular microhemorrhages, infarctions, or elevated Aβ (standardized uptake value ratio>1.2) were regressed on PD category using logistic models. We examined the interaction between Apolipoprotein E ε4 ( APOE ) allele possession and PD categories on the Aβ outcome. Results: Prevalence of baseline periodontal disease was 73% (959/1306) and 87% (206/248) among the MRI and PET subgroups, respectively. PD was not associated with volumetric brain measures nor microhemorrhages. PD was inversely associated with the odds of subcortical and lacunar infarctions. PD and Aβ were not associated in main effect or interaction analyses, although there was a notably stronger association among carriers of APOE . Conclusion: PD was not associated with altered brain structure, cerebral microhemorrhages or elevated Aβ deposition. Counter to the hypothesis, PD and complete tooth loss were inversely associated with cerebral infarctions.

Introduction: Studies have found that smaller brain volumes, cerebral infarcts, and white matter abnormalities are associated with dementia and mild cognitive impairment. However, these studies have been limited by short follow-up precluding a strong establishment of temporality. Therefore, it is unknown whether brain imaging findings are preceded by long-term changes in cognition. We sought to address this gap by examining brain imaging and two decades of cognitive changes in and a large, representative population-based cohort of older adults of black and white race. Hypothesis: We hypothesized that 22-year declines in global cognitive factor scores (GCFS) would be associated with a pattern of smaller total brain and temporal lobe meta region of interest (likely to be affected by Alzheimer’s disease) volumes, larger white matter hyperintensity volumes, and greater odds of ≥1 lacunar infarct and elevated brain β-amyloid deposition. Methods: ARIC participants with brain imaging data, complete cognitive factor score, and not missing key covariates were included. GCFS were collected at three visits across 22 years (1990-2013), and brain MRI and florbetapir PET imaging were collected in 2011-13; PET in subset of n=327. Mixed effects models with random intercepts and slopes predicted individual change in GCFS. Outcomes of interest were total brain volume (cc), temporal lobe meta region volume, log 2 (white matter hyperintensity volume), ≥1 lacunar infarct, and elevated brain β-amyloid deposition (SUVR >1.2). Multivariable linear and logistic regression was used to relate outcomes to GCFS slopes after adjusting for confounders, including vascular risk factors. As appropriate, models were also adjusted for total intracranial volume. Results: Among 1957 with complete brain MRI imaging, 1830 were included in the study, 60% (n=1096) women and 26% (n=480) black. At the first visit, the mean (SD) baseline age was 55 (5.2) yrs. The mean (SD) observed GCFS at the three visits were 0.16 (0.79), 0.05 (0.75), and -0.78 (0.86). After adjustment, a 1-SD larger decline in GCFS was significantly associated with a smaller brain volume by 1.6% [95%CI: 1.3, 1.8] relative to mean brain volume, a smaller temporal lobe meta region volume by 2.4% [2.1, 2.8] relative to the mean volume, a 15% [11, 19] larger volume of white matter hyperintensities, 1.3-fold [1.2, 1.4] higher odds of having ≥1 lacune, and 1.8-fold [1.4, 2.4] higher odds of elevated brain β-amyloid deposition. Associations remained significant after further adjustment for first or last GCFS. Conclusions: Greater declines in long-term cognitive functioning were significantly associated with smaller brain volumes and dementia-related brain characteristics and were independent of last visit GCFS. This suggests long-term changes in cognition may precede late-life brain morphology and outperform cross-sectional cognitive measures.

Background: Cerebral microbleeds (CMBs) are associated with cognitive decline, but their importance outside of clinical cerebral amyloid angiopathy is less well understood, as are the mechanisms of their impact on cognition. In a community-based dementia-free cohort, we evaluate cross-sectional associations between CMB patterns and cerebral amyloid β (Aβ) deposition, measured by florbetapir PET. Methods: ARIC-PET recruited nondemented individuals from 3 US sites. Participants completed 3T brain MRI with T2*GRE (with CMBs read for presence, frequency, location (lobar vs subcortical), and pattern, as well as florbetapir (Aβ) PET (global cortical standardized uptake value ratio >1.2 as a positive scan). Multivariable (see Table) logistic regression models of Aβ+ scans evaluated CMB presence, frequency, location, and pattern, in separate models. Effect modification by sex, race, APOE status, and cognition (normal vs mild cognitive impairment) was evaluated. Results: Nearly 25% of the 322 individuals included had CMBs. No significant associations were found between CMBs (presence or number) and Aβ positivity, but a pattern of isolated lobar CMBs or superficial siderosis was associated with over a 4-fold higher odds of elevated Aβ vs having no CMBs, without a similar elevated risk in those with isolated subcortical CMBs or mixed subcortical + either lobar CMBs or superficial siderosis. Although no significant interactions were found, a mixed pattern was nonsignificantly protective (OR estimates 0.4-0.6) and lobar only CMBs had a (nonsignificantly) higher risk (OR up to 6.4) of Aβ for three subgroups: women (vs men); Blacks (vs whites), APOE ε4 noncarriers (vs carriers), and cognitively normal (vs MCI). Conclusions: A lobar-only pattern of CMBs is most strongly associated with brain Aβ, with no elevated risk for a mixed CMB pattern. Further study is needed to understand differences in these CMB patterns and their meaning across distinct demographic subgroups.

Background Atrial fibrillation (AF) is a risk factor for cognitive decline, possibly from silent brain infarction. Left atrial changes in structure or function (atrial cardiopathy) can lead to AF but may impact cognition independently. It is unknown if AF or atrial cardiopathy also acts on Alzheimer disease–specific mechanisms, such as deposition of β‐amyloid. Methods and Results A total of 316 dementia‐free participants from the ARIC (Atherosclerosis Risk in Communities) study underwent florbetapir positron emission tomography, electrocardiography, and 2‐dimensional echocardiography. Atrial cardiopathy was defined as ≥1: (1) left atrial volume index >34 mL/m 2 ; (2) P‐wave terminal force >5000 µV×ms; and (3) serum NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) >250 pg/mL. Cross‐sectional associations between global cortical β‐amyloid (>1.2 standardized uptake value ratio) and adjudicated history of AF and atrial cardiopathy, each, were evaluated using multivariable logistic regression. Participants (mean age, 76 years) were 56% women and 42% Black individuals. Odds of elevated florbetapir standardized uptake value ratio were significantly increased among those with atrial cardiopathy (odds ratio, 1.81; 95% CI, 1.02–3.22) and doubled for those with enlarged left atrial volume index after adjustment for demographics/risk factors (95% CI, 1.04–4.61). There was no association between P‐wave terminal force or NT‐proBNP and elevated florbetapir standardized uptake value ratio, nor between AF and elevated standardized uptake value ratio. Conclusions Among healthy, nondemented community‐dwelling older individuals, we report an association between atrial cardiopathy, left atrial volume index, and elevated brain amyloid, by positron emission tomography, without a similar association in individuals with AF. Potential limitations include reverse causation and survival bias. Ongoing work will help determine if changes in cardiac structure and function precede or occur simultaneously with amyloid deposition.

Background and Purpose— Cardiovascular disease is a known risk factor for cognitive decline, although the mechanisms remain unclear. We hypothesize that Aβ (β-amyloid), a core pathology of Alzheimer's disease, will be associated with subclinical cardiac structure and function echocardiogram indices. Methods— Three hundred six nondemented participants from the ARIC study (Atherosclerosis Risk in Communities Study) underwent florbetapir positron emission tomography and 2D echocardiography (echo). Cross-sectional associations between echo markers of left ventricular structure and function and global cortical Aβ (≥1.2 standardized uptake value ratio were evaluated using multivariable logistic regression with interaction terms when appropriate. Results— Participants ranged in age from 67 to 88 years, were 57% female and 42% black. Per 1 cm increase in end-diastolic left ventricular diameter, the odds of elevated florbetapir standardized uptake value ratio doubled (odds ratio, 2.04 [95% CI, 1.10–3.77]), with similar findings when excluding mild cognitive impairment (odds ratio, 2.61 [95% CI, 1.22–5.59]). Conclusions— We have demonstrated a significant association between a marker of left ventricular structure and elevated florbetapir standardized uptake value ratio, identified using positron emission tomography. Ongoing prospective work will help determine if changes in cardiac structure and function either precede, or occur simultaneously with deposition of amyloid.