Imaging Markers of Vascular Brain Health: Quantification, Clinical Implications, and Future Directions

Cerebrovascular disease (CVD) manifests through a broad spectrum of mechanisms that negatively impact brain and cognitive health. Oftentimes, CVD changes (excluding acute stroke) are insufficiently considered in aging and dementia studies which can lead to an incomplete picture of the etiologies contributing to the burden of cognitive impairment. Our goal with this focused review is 3-fold. First, we provide a research update on the current magnetic resonance imaging methods that can measure CVD lesions as well as early CVD-related brain injury specifically related to small vessel disease. Second, we discuss the clinical implications and relevance of these CVD imaging markers for cognitive decline, incident dementia, and disease progression in Alzheimer disease, and Alzheimer-related dementias. Finally, we present our perspective on the outlook and challenges that remain in the field. With the increased research interest in this area, we believe that reliable CVD imaging biomarkers for aging and dementia studies are on the horizon.

Intravenous Thrombolysis After First-Ever Ischemic Stroke and Reduced Incident Dementia Rate

Background and Purpose: The use of intravenous thrombolysis is associated with improved clinical outcomes. Whether thrombolysis is associated with reduced incidence of poststroke dementia remains uncertain. We sought to estimate if the use of thrombolysis following first-ever ischemic stroke was associated with a reduced rate of incident dementia using a pragmatic observational design. Methods: We included first-ever ischemic stroke patients from the Ontario Stroke Registry who had not previously been diagnosed with dementia. The primary outcome was incident dementia ascertained by a validated diagnostic algorithm. We employed inverse probability of treatment-weighted Cox proportional hazard models to estimate the cause-specific hazard ratio for the association of thrombolysis and incident dementia at 1 and 5 years following stroke. Results: From July 2003 to March 2013, 7072 patients with ischemic stroke were included, 3276 (46.3%) were female and mean age was 71.0 (SD, 12.8) years. Overall, 38.2% of the cohort (n=2705) received thrombolysis, 77.2% (n=2087) of which was administered within 3 hours of stroke onset. In the first year following stroke, thrombolysis administration was associated with a 24% relative reduction in the rate of developing dementia (cause-specific hazard ratio, 0.76 [95% CI, 0.58–0.97]). This association remained significant at 5 years (cause-specific hazard ratio, 0.79 [95% CI, 0.66–0.91]) and at the end of follow-up (median 6.3 years; cause-specific hazard ratio, 0.79 [95% CI, 0.68–0.89]). Conclusions: Thrombolysis administration following first-ever ischemic stroke was independently associated with a reduced rate of dementia. Incident dementia should be considered as a relevant outcome when evaluating risk/benefit of thrombolysis in ischemic stroke patients.

Prevalence, Incidence, and Progression of Cognitive Impairment, No Dementia Among Rural-Dwelling Chinese Older Adults

Background: Few studies have examined occurrence and progression of cognitive impairment, no dementia (CIND) in rural China. Objective: To determine the prevalence and incidence of CIND in rural-dwelling Chinese older adults, and to examine risk and protective factors associated with progression to CIND and dementia. Methods: This population-based study included 2,781 dementia-free participants (age≥65 years) who were examined at baseline (2014) and followed in 2018. Demographic, epidemiological, clinical, and neuropsychological data were collected following a structured questionnaire. We defined CIND according to subjective cognitive complaints and the age- and education-specific Mini-Mental State Examination (MMSE) score. Data were analyzed with the multinomial logistic regression models. Results: The overall prevalence of CIND was 10.54% and the incidence was 28.26 per 1,000 person-years. CIND at baseline was associated with the multi-adjusted odds ratio (OR) of 2.06 (95% confidence interval = 1.23–3.47) for incident dementia. Multinomial logistic regression analysis suggested that compared with no CIND, the multi-adjusted OR of incident CIND was 2.21 (1.51–3.23) for women and 0.62 (0.38–0.99) for high social support, whereas the multi-adjusted OR of incident dementia was 1.14 (1.09–1.18) for older age, 0.29 (0.16–0.53) for high education, and 2.91 (1.47–5.74) for having a stroke history. Conclusion: CIND affects over one-tenth of older adults living in rural communities of western Shandong province. People with CIND are twice as likely to progress to dementia as people without CIND. Female sex, low education, stroke history, and low social support are associated with an increased risk of progression from normal cognition to CIND or dementia.

Frailty, lifestyle, genetics and dementia risk

ObjectiveTo optimise dementia prevention strategies, we must understand the complex relationships between lifestyle behaviours, frailty and genetics.MethodsWe explored relationships between frailty index, healthy lifestyle and polygenic risk scores (all assessed at study entry) and incident all-cause dementia as recorded on hospital admission records and death register data.ResultsThe analytical sample had a mean age of 64.1 years at baseline (SD=2.9) and 53% were women. Incident dementia was detected in 1762 participants (median follow-up time=8.0 years). High frailty was associated with increased dementia risk independently of genetic risk (HR 3.68, 95% CI 3.11 to 4.35). Frailty mediated 44% of the relationship between healthy lifestyle behaviours and dementia risk (indirect effect HR 0.95, 95% CI 0.95 to 0.96). Participants at high genetic risk and with high frailty had 5.8 times greater risk of incident dementia compared with those at low genetic risk and with low frailty (HR 5.81, 95% CI 4.01 to 8.42). Higher genetic risk was most influential in those with low frailty (HR 1.31, 95% CI 1.22 to 1.40) but not influential in those with high frailty (HR 1.09, 95% CI 0.92 to 1.28).ConclusionFrailty is strongly associated with dementia risk and affects the risk attributable to genetic factors. Frailty should be considered an important modifiable risk factor for dementia and a target for dementia prevention strategies, even among people at high genetic risk.

Diet and Dementia: A Prospective Study

Whether dietary and nutrition and dietary patterns are associated with the development of dementia is an interesting research question. Participants of a longitudinal cohort study that included European adults who were middle to old aged at baseline and who had not been diagnosed with dementia at baseline (2006–2010) and had not been diagnosed with dementia or died within 5 years after baseline were followed up (until 2018) and analyzed. Associations between intake frequency of each food class measured by the food-frequency questionnaire at baseline and incident dementia 5 years after baseline were analyzed after correcting for confounding variables. A total of approximately 340,000 participants and 900 cases were included in the analysis for each food class. Cox proportional hazard models with self-reported intake level of each food category divided into four mostly equally divided categorical variables revealed a high intake of bread, moderate total meat and total fish intake and low vegetable and fruit intake were thus associated with a small but significant decrease in the onset risk of dementia, while poultry and cereal were not. These findings are mostly inconsistent with the idea that Mediterranean diet is associated with lower risk of subsequent incident dementia.

Association of long-term body weight variability with dementia: a prospective study

Background Body weight variability (BWV) refers to intraindividual weight loss and gain over a period. The association of long-term BWV with dementia remains unclear and whether this association is beyond body weight change is undetermined. Methods In the Health and Retirement Study (HRS), a total of 5,547 dementia-free participants (56.7% women; mean [SD] age, 71.1 [3.2] years) at baseline (2008) were followed up to 8 years (mean=6.8 years) to detect incident dementia. Body weight was self-reported biennially from 1992-2008. BWV was measured as the coefficient of variation utilizing the body weight reported 9 times across 16 years before baseline. Cox proportional hazard model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI). Results Among the 5,547 participants, a total of 427 incident dementia cases were identified during follow-up. Greater long-term BWV was significantly associated with a higher risk of dementia (HR comparing extreme quartiles: 2.01, 95% CI: 1.48-2.72; HR of each SD increment: 1.21, 95% CI: 1.10-1.32; P-trend<0.001) independent of mean body weight and body weight change. This significant association was even observed for BWV estimated approximately 15 years preceding dementia diagnosis (HR of each SD increment: 1.13, 95% CI: 1.03-1.23) and was more pronounced for that closer to diagnosis. Conclusions Our prospective study suggested that greater BWV may be a novel risk factor for dementia.