Alzheimer's disease: role of size and location of white matter changes in determining cognitive deficits

White matter hyperintensities: a possible link between sarcopenia and cognitive impairment in patients with mild to moderate Alzheimer's disease

PURPOSE

Alzheimer's disease (AD) has been reported to be associated with sarcopenia. White matter hyperintensities (WMH) are common in AD patients. However, the effect of WMH on sarcopenia in AD remains unclear. We hence aimed to investigate the possible association between regional WMH volumes and sarcopenic parameters in AD.

METHODS

57 mild to moderate AD patients and 22 normal controls (NC) were enrolled. Sarcopenic parameters were assessed, including appendicular skeletal mass index (ASMI), grip strength, 5-times sit-to-stand (5-STS) time, and gait speed. The volumes of periventricular hyperintensities (PVH) and deep white matter hyperintensities (DWMH) were quantified using 3D-slicer software.

RESULTS

AD subjects exhibited a lower ASMI, a slower gait speed, an increased 5-STS time, and larger volumes of PVH and DWMH than those in the NC group. In AD subjects, total WMH and PVH volumes were related to cognitive impairment, particularly executive function decline. Moreover, total WMH volume and PVH volume were negatively correlated with gait speed across various clinical stages of AD. Multiple linear regression analysis showed that PVH volume was independently associated with 5-STS time and gait speed, whereas DWMH volume was only independently associated with gait speed.

CONCLUSION

WMH volume was associated with cognitive decline and various sarcopenic parameters. It thereby suggested that WMH may serve as the connection between sarcopenia and cognitive dysfunction in AD. Further studies are needed to confirm these findings and to determine whether sarcopenia interventions reduce WMH volume and improve cognitive function in AD.

Fractal dimension of the cortical gray matter outweighs other brain MRI features as a predictor of transition to dementia in patients with mild cognitive impairment and leukoaraiosis

Background

The relative contribution of changes in the cerebral white matter (WM) and cortical gray matter (GM) to the transition to dementia in patients with mild cognitive impairment (MCI) is not yet established. In this longitudinal study, we aimed to analyze MRI features that may predict the transition to dementia in patients with MCI and T2 hyperintensities in the cerebral WM, also known as leukoaraiosis.

Methods

Sixty-four participants with MCI and moderate to severe leukoaraiosis underwent baseline MRI examinations and annual neuropsychological testing over a 2 year period. The diagnosis of dementia was based on established criteria. We evaluated demographic, neuropsychological, and several MRI features at baseline as predictors of the clinical transition. The MRI features included visually assessed MRI features, such as the number of lacunes, microbleeds, and dilated perivascular spaces, and quantitative MRI features, such as volumes of the cortical GM, hippocampus, T2 hyperintensities, and diffusion indices of the cerebral WM. Additionally, we examined advanced quantitative features such as the fractal dimension (FD) of cortical GM and WM, which represents an index of tissue structural complexity derived from 3D-T1 weighted images. To assess the prediction of transition to dementia, we employed an XGBoost-based machine learning system using SHapley Additive exPlanations (SHAP) values to provide explainability to the machine learning model.

Results

After 2 years, 18 (28.1%) participants had transitioned from MCI to dementia. The area under the receiving operator characteristic curve was 0.69 (0.53, 0.85) [mean (90% confidence interval)]. The cortical GM-FD emerged as the top-ranking predictive feature of transition. Furthermore, aggregated quantitative neuroimaging features outperformed visually assessed MRI features in predicting conversion to dementia.

Discussion

Our findings confirm the complementary roles of cortical GM and WM changes as underlying factors in the development of dementia in subjects with MCI and leukoaraiosis. FD appears to be a biomarker potentially more sensitive than other brain features.

Topographical differences in white matter hyperintensity burden and cognition in aging, MCI, and AD

White matter hyperintensities (WMHs) are pathological changes that occur with increased age and are associated with cognitive decline. Most WMH research has not examined regional differences and focuses on a whole-brain approach. This study examined regional WMHs between normal controls (NCs), people with mild cognitive impairment (MCI), and Alzheimer's disease (AD). We also examined whether WMHs were associated with cognitive decline. Participants from the Alzheimer's Disease Neuroimaging Initiative were included if they had at least one WMH measurement and cognitive scores examining global cognition, executive functioning, and memory. Only amyloid-positive MCI and AD participants were included. A total of 1573 participants with 7381 timepoints over a maximum period of 13 years were included. Linear mixed-effects models examined group differences in WMH burden and associations between WMH burden and cognition. People with MCI and AD had increased total and regional WMHs compared to NCs. An association between WMHs and cognition was observed for global cognition, executive functioning, and memory in NCs in all regions. A steeper decline (stronger association between WMH and cognition) was observed in MCI compared to NCs for all cognitive domains in all regions. A steeper decline was observed in AD compared to NCs for global cognition in only the temporal region. A strong association is observed between all cognitive domains of interest and WMH burden in healthy aging and MCI, while those with AD only had a few associations between WMH and global cognition. These findings suggest that the WMH burden is associated with changes in cognition in healthy aging and early cognitive decline.

White matter hyperintensity topography in Alzheimer's disease and links to cognition

Introduction

White matter hyperintensities (WMH) are often described in Alzheimer's disease (AD), but their topography and specific relationships with cognition remain unclear.

Methods

Regional WMH were estimated in 54 cognitively impaired amyloid beta–positive AD (Aβpos‐AD), compared to 40 cognitively unimpaired amyloid beta–negative older controls (Aβneg‐controls) matched for vascular risk factors. The cross‐sectional association between regional WMH volume and cognition was assessed within each group, controlling for cerebral amyloid burden, global cortical atrophy, and hippocampal atrophy.

Results

WMH volume was larger in Aβpos‐AD compared to Aβneg‐controls in all regions, with the greatest changes in the splenium of the corpus callosum (S‐CC). In Aβpos‐AD patients, larger total and regional WMH volume, especially in the S‐CC, was strongly associated with decreased cognition.

Discussion

WMH specifically contribute to lower cognition in AD, independently from amyloid deposition and atrophy. This study emphasizes the clinical relevance of WMH in AD, especially posterior WMH, and most notably S‐CC WMH.

Sleep-Wake Cycle in Alzheimer's Disease Is Associated with Tau Pathology and Orexin Dysregulation

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia. It is mainly characterized by a progressive deterioration of cognition, but sleep-wake cycle disturbances frequently occur. Irregular sleep-wake cycle, insomnia, and daytime napping usually occur in patients with AD in the course of the disease.

OBJECTIVE

The aim of the present study was to verify the sleep-wake cycle in mild to moderate AD patients compared to controls, and to evaluate the relationship between the sleep-wake cycle impairment and the neuropsychological testing, CSF AD biomarkers, and CSF orexin concentrations.

METHODS

Mild to moderate AD patients were enrolled and underwent 14-day actigraphic recording, sleep diary, neuropsychological testing, and CSF biomarkers analysis. All patients were compared to controls.

RESULTS

Eighteen AD patients were compared to ten controls. AD patients showed the alteration of the sleep-wake cycle, featured by sleep dysregulation and daytime wake fragmentation, with respect to controls. Considering the correlation analysis, we documented the correlation between tau proteins and orexin CSF levels and sleep-wake cycle dysregulation.

CONCLUSION

This study confirmed the dysregulation of sleep-wake cycle in AD patients, as reflected by the daytime wake fragmentation, irregular sleep-wake rhythm, and nocturnal sleep impairment. This sleep-wake cycle disorder correlates with AD neuropathological in vivo features and brain orexin activity. Hence, we suppose that a more marked AD pathology coupled with orexinergic system dysregulation may promote sleep-wake cycle impairment in AD patients.

White Matter Hyperintensities and Cognition in Mild Cognitive Impairment and Alzheimer's Disease: A Domain-Specific Meta-Analysis

BACKGROUND

White matter hyperintensities (WMHs) are related to cognitive dysfunction in the general population. The clinical relevance of WMHs in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) is, however, unclear.

OBJECTIVE

This meta-analysis aimed to quantify the association of WMHs and specific cognitive domains in patients with MCI or AD.

METHODS

PubMed (January 1990-January 2017) was searched for studies that used MRI to quantify WMHs, and measured cognitive functioning (≥1 predefined cognitive domain with ≥1 test) in a well-defined population of persons diagnosed with MCI or AD. Fischer's Z was used as the common metric for effect size. Modifying effects of demographics, MMSE, and WMH location were examined.

RESULTS

Twelve cross-sectional studies on AD (total n = 1,370, median age 75 years) and 10 studies on MCI (9 cross-sectional, 1 longitudinal; total n = 2,286, median age 73 years) were included. The association between WMHs and overall cognition was significantly stronger for MCI (-0.25, -0.36 to -0.14) than for AD (-0.11, -0.14 to -0.08; QM = 10.7, p < 0.05). For both groups, largest effect sizes were found in attention and executive functions (-0.26, -0.36 to -0.15) and processing speed (-0.21, -0.35 to -0.12). No significant modifying effects of age and gender were found.

CONCLUSION

WMHs have a medium-sized association with different cognitive functions in patients with MCI and a small, but statistically significant, association with cognition in AD. These result underscore the role of co-occurring vascular brain damage in MCI and AD.

White Matter Changes in Patients with Alzheimer's Disease and Associated Factors

Alzheimer's disease (AD) is traditionally thought of as a neurodegenerative disease. Recent evidence shows that beta amyloid-independent vascular changes and beta amyloid-dependent neuronal dysfunction both equally influence the disease, leading to loss of structural and functional connectivity. White matter changes (WMCs) in the brain are commonly observed in dementia patients. The effect of vascular factors on WMCs and the relationship between WMCs and severity of AD in patients remain to be clarified. We recruited 501 clinically diagnosed probable AD patients with a series of comprehensive neuropsychological tests and brain imaging. The WMCs in cerebral CT or MRI were rated using both the modified Fazekas scale and the combined CT-MRI age related WMC (ARWMC) rating scale. Periventricular WMCs were observed in 79.4% of the patients and deep WMCs were also seen in 48.7% of the patients. WMC scores were significantly higher in the advanced dementia stage in periventricular WMCs (p = 0.001) and total ARWMCs (p < 0.001). Age and disease severity were both independently associated with WMCs score, particularly in the total, frontal and parieto-occipital areas. Vascular factors including hypertension, diabetes mellitus, and gender were not significantly associated with WMCs. In conclusion, both age and severity of dementia were significantly associated with WMCs in AD patients. These associations highlight future research targets.

MRI-based evaluation of structural degeneration in the ageing brain: Pathophysiology and assessment

Advances in MRI technology have significantly contributed to our ability to understand the process of brain ageing, allowing us to track and assess changes that occur during normal ageing and neurological conditions. This paper focuses on reviewing structural changes of the ageing brain that are commonly seen using MRI, summarizing the pathophysiology, prevalence, and neuroanatomical distribution of changes including atrophy, lacunes, white matter lesions, and dilated perivascular spaces. We also review the clinically accessible methodology for assessing these MRI-based changes, covering visual rating scales, as well computer-aided and fully automated methods. Subsequently, we consider novel assessment methods designed to evaluate changes across the whole brain, and finally discuss new directions in this field of research.

Analysis of correlation between cerebral perfusion and KIM score of white matter lesions in patients with Alzheimer's disease

PURPOSE

This study aimed to characterize white matter lesions (WMLs) and regional cerebral perfusion, and evaluate their correlations with cognitive deficits in Alzheimer's disease (AD) patients.

PATIENT AND METHODS

One hundred and twenty-eight patients with AD (AD group) and 75 subjects without AD (control group) were recruited. The medical information was collected from each subject. Montreal cognitive assessment (MoCA) was employed for the assessment of cognition. Cranial MRI was performed, and the KIM scoring system was used to evaluate the white matter hyperintensity. The CT perfusion (CTP) imaging was employed to assess the whole cerebral perfusion, and the region of interest (ROI) was selected to determine the blood perfusion at different parts.

RESULTS

The education level and MoCA score in AD group were significantly lower than in control group (P<0.001). The KIM score of juxtaventricular WML (JVWMLs) was significantly different between two groups (P<0.05) and AD group showed a higher incidence of severe JVWML and periventricular WML (PVWMLs); in AD group, the total KIM score and KIM scores of JVWMLs, PVWMLs and deep WML (DWMLs) showed negative relationships with the MoCA score (P<0.001). As compared to control group, the blood perfusion of either whole brain or different parts in the AD group reduced significantly (P<0.05). In the AD group, there was a negative correlations of blood perfusion at JVWM and PVWM with corresponding KIM scores (P<0.05 or 0.01). In the AD group, the blood perfusions of the whole brain, JVWMLs, PVWMLs and deep WML were negatively related to MoCA score (P<0.05).

CONCLUSION

In conclusion, the cognitive deficits in the AD patients are associated with the degree of WMLs, especially the JVWML, PVWML and DWML as well as with the reduced perfusion of JVWM, PVWM and deep WM.

Age-dependent cognitive and affective differences in Alzheimer's and Parkinson's diseases in relation to MRI findings

OBJECTIVE

To compare age-dependent changes in cognitive and affective functions related to white matter changes between patients with Alzheimer's disease (AD) and Parkinson's disease (PD).

METHODS

We retrospectively compared age-dependent cognitive and affective functions in 216 AD patients, 153 PD patients, and 103 healthy controls with cerebral white matter lesions (WMLs), periventricular hyperintensity (PVH), deep white matter hyperintensity (DWMH), micro-bleeds (MBs), and lacunar infarcts (LIs).

RESULTS

The average mini-mental state examination (MMSE) scores were 19.6±6.1 and 26.8±3.6 in AD and PD patients, respectively. Significant decreases were found in the MMSE score, Hasegawa's dementia scale-revised (HDS-R) score, frontal assessment battery score, and Abe's BPSD score (ABS) among the age-dependent AD subgroups and in the MMSE, HDS-R, Montreal cognitive assessment, geriatric depression scale, and ABS scores among the age-dependent PD subgroups; they were worse in AD patients. White matter changes were observed in >88% and >72% of patients with AD and PD, respectively. An age-dependent direct comparison of AD and PD showed significant differences in the PVH and DWMH grades, and numbers of MBs and LIs.

CONCLUSION

WML-related cognitive and affective functions worsen with age in AD and PD patients; however, the abnormalities were more frequent and stronger in AD patients.

Candidate-gene analysis of white matter hyperintensities on neuroimaging

BACKGROUND

White matter hyperintensities (WMH) are a common radiographic finding and may be a useful endophenotype for small vessel diseases. Given high heritability of WMH, we hypothesised that certain genotypes may predispose individuals to these lesions and consequently, to an increased risk of stroke, dementia and death. We performed a meta-analysis of studies investigating candidate genes and WMH to elucidate the genetic susceptibility to WMH and tested associated variants in a new independent WMH cohort. We assessed a causal relationship of WMH to methylene tetrahydrofolate reductase (MTHFR).

METHODS

Database searches through March 2014 were undertaken and studies investigating candidate genes in WMH were assessed. Associated variants were tested in a new independent ischaemic cohort of 1202 WMH patients. Mendelian randomization was undertaken to assess a causal relationship between WMH and MTHFR.

RESULTS

We identified 43 case-control studies interrogating eight polymorphisms in seven genes covering 6,314 WMH cases and 15,461 controls. Fixed-effects meta-analysis found that the C-allele containing genotypes of the aldosterone synthase CYP11B2 T(-344)C gene polymorphism were associated with a decreased risk of WMH (OR=0.61; 95% CI, 0.44 to 0.84; p=0.003). Using mendelian randomisation the association among MTHFR C677T, homocysteine levels and WMH, approached, but did not reach, significance (expected OR=1.75; 95% CI, 0.90-3.41; observed OR=1.68; 95% CI, 0.97-2.94). Neither CYP11B2 T(-344)C nor MTHFR C677T were significantly associated when tested in a new independent cohort of 1202 patients with WMH.

CONCLUSIONS

There is a genetic basis to WMH but anonymous genome wide and exome studies are more likely to provide novel loci of interest.

Genetic associations of leukoaraiosis indicate pathophysiological mechanisms in white matter lesions etiology

Leukoaraiosis (LA), also called white matter lesions (WMLs) and white matter hyperintensities (WMHs), is a frequent neuroimaging finding commonly seen on magnetic resonance imaging brain scans of elderly people with prevalence ranging from 50% to 100%. Although it remains asymptomatic, LA is not considered to be benign, and it is showed to be related to a host of poor clinical outcomes and increases the risk of disability, dementia, depression, stroke, and the overall morbidity and mortality. Pathologically, LA is characterized by loss of myelin and axons, patchy demyelination, and denudation of ependyma in regions of WMH. Age and hypertension are the most importantly established risk factors for LA. However, the precise pathogenic mechanisms remain unclear. Together with the previous findings, our recent genetic results strongly supported that LA is associated with immune response and neuroinflammation. Therefore, we confidently hypothesized that LA was not only a common neuroimaging phenomenon in the elderly but also an emerging neuroinflammatory disorder in the central nervous system. This article focusing on neuroimaging classification, genetics basis, and putative molecular mechanism introduced the basic knowledge and current status of LA and put forward some of our research ideas and results from our molecular genetics research, which may pave the way for deciphering the putative pathogenic mechanism, risk factor, epigenetic index, and its application in diagnostic agents or drug target for prevention and treatment. Thus, it could provide clinicians and researchers with a specific and modern overview of LA to enable the understanding of recent progress and future directions in this illness.

Considerations for the Optimization of Induced White Matter Injury Preclinical Models

White matter (WM) injury in relation to acute neurologic conditions, especially stroke, has remained obscure until recently. Current advances in imaging technologies in the field of stroke have confirmed that WM injury plays an important role in the prognosis of stroke and suggest that WM protection is essential for functional recovery and post-stroke rehabilitation. However, due to the lack of a reproducible animal model of WM injury, the pathophysiology and mechanisms of this injury are not well studied. Moreover, producing selective WM injury in animals, especially in rodents, has proven to be challenging. Problems associated with inducing selective WM ischemic injury in the rodent derive from differences in the architecture of the brain, most particularly, the ratio of WM to gray matter in rodents compared to humans, the agents used to induce the injury, and the location of the injury. Aging, gender differences, and comorbidities further add to this complexity. This review provides a brief account of the techniques commonly used to induce general WM injury in animal models (stroke and non-stroke related) and highlights relevance, optimization issues, and translational potentials associated with this particular form of injury.

Diffusion tensor imaging in Alzheimer's disease and affective disorders

The functional organization of the brain in segregated neuronal networks has become a leading paradigm in the study of brain diseases. Diffusion tensor imaging (DTI) allows testing the validity and clinical utility of this paradigm on the structural connectivity level. DTI in Alzheimer's disease (AD) suggests a selective impairment of intracortical projecting fiber tracts underlying the functional disorganization of neuronal networks supporting memory and other cognitive functions. These findings have already been tested for their utility as clinical markers of AD in large multicenter studies. Affective disorders, including major depressive disorder (MDD) and bipolar disorder (BP), show a high comorbidity with AD in geriatric populations and may even have a pathogenetic overlap with AD. DTI studies in MDD and BP are still limited to small-scale monocenter studies, revealing subtle abnormalities in cortico-subcortial networks associated with affect regulation and reward/aversion control. The clinical utility of these findings remains to be further explored. The present paper presents the methodological background of diffusion imaging, including DTI and diffusion spectrum imaging, and discusses key findings in AD and affective disorders. The results of our review strongly point toward the necessity of large-scale multicenter multimodal transnosological networks to study the structural and functional basis of neuronal disconnection underlying different neuropsychiatric diseases.

Cognitive impairments associated with medial temporal atrophy and white matter hyperintensities: an MRI study in memory clinic patients

In this retrospective study, we investigated the independent effects of white matter hyperintensities (WMH) and hippocampal atrophy on cognitive functions in a broad sample of patients seen in a memory clinic. To ensure generalizability, these associations were examined irrespective of diagnosis and with minimal exclusion criteria. Next to these independent effects, interactions between WMH and hippocampal atrophy were examined. Between January 2006 and September 2011 a total of 500 patients visited the memory clinic, 397 of whom were included. Magnetic resonance images of 397 patients were visually analyzed for WMH, medial temporal atrophy (MTA), and global atrophy. We evaluated the association of WMH and MTA with the following cognitive domains: global cognition, episodic memory, working memory, executive function and psychomotor speed. Main effects and interaction effects were examined by means of correlation and regression analyses. In the regression analyses, we controlled for potential confounding effects of global atrophy. The correlational results revealed that WMH were associated with global cognition, executive function and psychomotor speed, whereas a trend was found for episodic memory. MTA was associated with all these four cognitive domains; an additional trend was observed for working memory. Hierarchical regression analyses revealed main independent effects of MTA for episodic memory, executive function, psychomotor speed and global cognition; WMH were only associated with global cognition. The interaction between MTA and WMH was significant for episodic memory only. This study demonstrates that predominantly MTA is an independent predictor not only for memory function, with which is it classically associated, but also for global cognition and executive function. Taken together, MTA may be an important correlate of cognitive deficits found in people attending the memory clinic.

APOE genotype and MRI markers of cerebrovascular disease: systematic review and meta-analysis

OBJECTIVE

We aimed to examine the association of APOE ε genotype with MRI markers of cerebrovascular disease (CVD): white matter hyperintensities, brain infarcts, and cerebral microbleeds.

METHODS

We performed a systematic review and meta-analysis of 42 cross-sectional or longitudinal studies identified in PubMed from 1966 to June 2012 (n = 29,965). This included unpublished data from 3 population-based studies: 3C-Dijon, Framingham Heart Study, and Sydney Memory and Ageing Study. When necessary, authors were contacted to provide effect estimates for the meta-analysis.

RESULTS

APOE ε4 carrier status and APOE ε44 genotype were associated with increasing white matter hyperintensity burden (sample size-weighted z score meta-analysis [meta]-p = 0.0034 and 0.0030) and presence of cerebral microbleeds (meta odds ratio [OR] = 1.24, 95% confidence interval [CI] [1.07, 1.43], p = 0.004, and 1.87 [1.26, 2.78], p = 0.002), especially lobar. APOE ε2 carrier status was associated with increasing white matter hyperintensity load (z score meta-p = 0.00053) and risk of brain infarct (meta OR = 1.41[1.09, 1.81], p = 0.008).

CONCLUSIONS

APOE ε4 and APOE ε2 were associated with increasing burden in MRI markers for both hemorrhagic and ischemic CVD. While the association of APOE ε4 with an increased burden of CVD could be partly contributing to the relationship between APOE ε4 and AD, APOE ε2 was associated with MRI markers of CVD in the opposite direction compared to AD.

Cognitive aging in persons with minimal amyloid-β and white matter hyperintensities

Substantial individual differences exist in the magnitude of the cognitive decline associated with normal aging. Potential contributors to this intersubject variability include white matter hyperintensities (WMH) and preclinical Alzheimer's disease, evident as increased brain amyloid. This study examined whether older individuals with minimal evidence of WMH and/or brain amyloid-beta (seen on positron emission tomography with the Pittsburgh compound B radiotracer-PiB) still showed significant cognitive decrements compared to the young. Older individuals, conservatively screened for normal range performance on an extensive neuropsychological battery, underwent structural magnetic resonance imaging (MRI) and PiB scans and performed tests of information processing speed, working memory and inhibitory function. The elderly were divided into PiB(+) and PiB(-) groups based on radiotracer retention. There were no significant differences in cognitive performance between PiB(+) and PiB(-) elderly. However, both PiB groups performed significantly worse than did the young on cognitive testing. WMH burden in the same individuals was quantified by consensus ratings using a 10 point scale with a median split defining two groups, WMH(+) and WMH(-). There were no differences in cognitive performance between WMH(+) and WMH(-) individuals, but both WMH groups performed significantly worse than did the young. Older participants who were both PiB(-) and WMH(-) also performed significantly worse than did the young in all three cognitive domains. The present results suggest that normal-elderly individuals whose brain scans show minimal evidence of amyloid deposition or WMH, still demonstrate a major decrement in comparison to younger persons on measures of processing resources and inhibitory efficiency.

Effect of white matter lesions on brain perfusion in Alzheimer's disease

BACKGROUND

This study examined the effect of white matter lesions (WMLs) on regional cerebral blood flow (rCBF) in patients with Alzheimer's disease (AD).

METHODS

Ninety-eight patients with AD were included in the study (40 men and 58 women; mean age, 78.1 years). Cognitive function was assessed using the Mini-Mental State Examination. Brain magnetic resonance imaging (MRI) and (99m)Tc ethyl cysteinate dimer single photon emission computed tomography were performed in all subjects. AD patients were divided into two subgroups according to the presence of WMLs on MRI. A voxel-by-voxel group analysis using Statistical Parametric Mapping 8 was used to detect the differences in rCBF between the two groups.

RESULTS

Fifty-seven of 98 AD patients (58%) showed mild to moderate WMLs on MRI. The prevalence of hypertension was significantly higher in AD patients with WMLs than in those without WMLs. AD patients with WMLs exhibited a significantly decreased rCBF in the anterior cingulate gyrus and insula, compared to AD patients without WMLs.

CONCLUSION

We suggest that WMLs might influence brain regions associated with the limbic system in patients with AD.

Obstructive sleep apnea as a risk factor for cerebral white matter change in a middle-aged and older general population

STUDY OBJECTIVE

Obstructive sleep apnea (OSA) contributes to the development of systemic hypertension, and hypertension strongly predicts the development of white matter change (WMC). Thus, it is plausible that OSA mediates WMC. The goal of the current study is to determine whether a contextual relationship exists between OSA and cerebral WMC.

DESIGN

Cross-sectional analyses conducted in a population-based study.

SETTING

Korean community-based sample from the Korean Genome and Epidemiology Study (KoGES) who attended examinations in 2011 at a medical center.

PARTICIPANTS

There were 503 individuals (mean ± SD, age 59.63 ± 7.48 y) who were free of previously diagnosed cardiovascular and neurologic diseases.

MEASUREMENTS AND RESULTS

Participants underwent 1-night polysomnography and were classified as no OSA (obstructive apnea-hypopnea index [AHI] < 5, n = 289), mild OSA (AHI 5-15, n = 161), and moderate to severe OSA (AHI ≥ 15, n = 53). WMC was identified with brain magnetic resonance imaging (MRI) and was found in 199 individuals (39.56%). Multivariate logistic regression analyses adjusted for covariates revealed that moderate to severe OSA was significantly associated with the presence of WMC (odds ratio [OR] 2.08, 95%, confidence interval [CI] 1.05-4.13) compared with no OSA. Additional adjustment of hypertension to the model did not alter the significance of the association (OR 2.03, 95% CI 1.02-4.05).

CONCLUSIONS

Moderate to severe OSA is an independent risk factor for WMC in middle-aged and older individuals. Thus, early recognition and treatment of OSA could reduce the risk of stroke and vascular dementia.

Deep versus periventricular white matter lesions and cognitive function in a community sample of middle-aged participants

The association of cerebral white matter lesions (WMLs) with cognitive status is not well understood in middle-aged individuals. Our aim was to determine the specific contribution of periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) to cognitive function in a community sample of asymptomatic participants aged 50 to 65 years. One hundred stroke- and dementia-free adults completed a comprehensive neuropsychological battery and brain MRI protocol. Participants were classified according to PVH and DWMH scores (Fazekas scale). We dichotomized our sample into low grade WMLs (participants without or with mild lesions) and high grade WMLs (participants with moderate or severe lesions). Analyses were performed separately in PVH and DWMH groups. High grade DWMHs were associated with significantly lower scores in executive functioning (-0.45 standard deviations [SD]), attention (-0.42 SD), verbal fluency (-0.68 SD), visual memory (-0.52 SD), visuospatial skills (-0.79 SD), and psychomotor speed (-0.46 SD). Further analyses revealed that high grade DWMHs were also associated with a three- to fourfold increased risk of impaired scores (i.e.,<1.5 SD) in executive functioning, verbal fluency, visuospatial skills, and psychomotor speed. Our findings suggest that only DWMHs, not PVHs, are related to diminished cognitive function in middle-aged individuals. (JINS, 2012, 18, 1-12).

Prevalence of sleep disturbances in mild cognitive impairment and dementing disorders: a multicenter Italian clinical cross-sectional study on 431 patients

BACKGROUND/AIMS

Sleep disturbances are common in the elderly and in persons with cognitive decline. The aim of this study was to describe frequency and characteristics of insomnia, excessive daytime sleepiness, sleep-disordered breathing, REM behavior disorder and restless legs syndrome in a large cohort of persons with mild cognitive impairment or dementia.

METHODS

431 consecutive patients were enrolled in 10 Italian neurological centers: 204 had Alzheimer's disease, 138 mild cognitive impairment, 43 vascular dementia, 25 frontotemporal dementia and 21 Lewy body dementia or Parkinson's disease dementia. Sleep disorders were investigated with a battery of standardized questions and questionnaires.

RESULTS

Over 60% of persons had one or more sleep disturbances almost invariably associated one to another without any evident and specific pattern of co-occurrence. Persons with Alzheimer's disease and those with mild cognitive impairment had the same frequency of any sleep disorder. Sleep-disordered breathing was more frequent in vascular dementia. REM behavior disorder was more represented in Lewy body or Parkinson's disease dementia.

CONCLUSION

A careful clinical evaluation of sleep disorders should be performed routinely in the clinical setting of persons with cognitive decline. Instrumental supports should be used only in selected patients.

Aspirin for the prevention of cognitive decline in the elderly: rationale and design of a neuro-vascular imaging study (ENVIS-ion)

BACKGROUND

This paper describes the rationale and design of the ENVIS-ion Study, which aims to determine whether low-dose aspirin reduces the development of white matter hyper-intense (WMH) lesions and silent brain infarction (SBI). Additional aims include determining whether a) changes in retinal vascular imaging (RVI) parameters parallel changes in brain magnetic resonance imaging (MRI); b) changes in RVI parameters are observed with aspirin therapy; c) baseline cognitive function correlates with MRI and RVI parameters; d) changes in cognitive function correlate with changes in brain MRI and RVI and e) whether factors such as age, gender or blood pressure influence the above associations.

METHODS/DESIGN

Double-blind, placebo-controlled trial of three years duration set in two Australian academic medical centre outpatient clinics. This study will enrol 600 adults aged 70 years and over with normal cognitive function and without overt cardiovascular disease. Subjects will undergo cognitive testing, brain MRI and RVI at baseline and after 3 years of study treatment. All subjects will be recruited from a 19,000-patient clinical outcome trial conducted in Australia and the United States that will evaluate the effects of aspirin in maintaining disability-free longevity over 5 years. The intervention will be aspirin 100 mg daily versus matching placebo, randomized on a 1:1 basis.

DISCUSSION

This study will improve understanding of the mechanisms at the level of brain and vascular structure that underlie the effects of aspirin on cognitive function. Given the limited access and high cost of MRI, RVI may prove useful as a tool for the identification of individuals at high risk for the development of cerebrovascular disease and cognitive decline.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01038583.

White Matter Changes in Bipolar Disorder, Alzheimer Disease, and Mild Cognitive Impairment: New Insights from DTI

Neuropathological and neuroimaging studies have reported significant changes in white matter in psychiatric and neurodegenerative diseases. Diffusion tensor imaging (DTI), a recently developed technique, enables the detection of microstructural changes in white matter. It is a noninvasive in vivo technique that assesses water molecules' diffusion in brain tissues. The most commonly used parameters are axial and radial diffusivity reflecting diffusion along and perpendicular to the axons, as well as mean diffusivity and fractional anisotropy representing global diffusion. Although the combination of these parameters provides valuable information about the integrity of brain circuits, their physiological meaning still remains controversial. After reviewing the basic principles of DTI, we report on recent contributions that used this technique to explore subtle structural changes in white matter occurring in elderly patients with bipolar disorder and Alzheimer disease.

Historical note on Darwin's consideration of early-onset dementia in older persons, thirty-six years before Alzheimer's initial case report

In February 1871, the great naturalist Charles Darwin received a letter from Dr. James-Crichton Browne, who was serving as Director of the largest lunatic asylum in England. Darwin had been introduced to Crichton-Browne 2 years earlier by Henry Maudsley, who believed that the young psychiatrist could provide Darwin with clinical examples of extreme emotional expression, to aid him in preparing to write Expression of the Emotions in Man and Animals (1872). This particular letter from Crichton-Browne contained the first and only reference to "premature dotage" or "senile decay" found anywhere in Darwin's entire corpus of correspondence, which amounted to more than 80,000 pages of handwritten letters to nearly 2,000 individuals throughout his lifetime. Moreover, this letter from Crichton-Browne, received by Darwin 36 years before the first case report of senile dementia by Professor Alois Alzheimer, explicitly noted that such premature dotage is the result of "brain wasting." Crichton-Browne believed that senile dementia was the result of a central nervous system disease, with the emotional lability observed in his patients linked inextricably to the disease process. This early hypothesis, of interest to Darwin in 1871, anticipated the groundbreaking neurohistopathologic research and case description by Alzheimer 36 years later, and has been confirmed by all clinical research in this field since 1907. This concordance between psychological symptoms and Alzheimer's disease continues to be an important area of study, leading to recent advances in our understanding of the genetics, neurobiology, and neurochemistry of psychiatric illness in older adults.

The impact of vascular burden on late-life depression

Small vessel pathology and microvascular lesions are no longer considered as minor players in the fields of cognitive impairment and mood regulation. Although frequently found in cognitively intact elders, both neuroimaging and neuropathological data revealed the negative impact on cognitive performances of their presence within neocortical association areas, thalamus and basal ganglia. Unlike cognition, the relationship between these lesions and mood dysregulation is still a matter of intense debate. Early studies focusing on the role of macroinfarct location in the occurrence of post-stroke depression (PSD) led to conflicting data. Later on, the concept of vascular depression proposed a deleterious effect of subcortical lacunes and deep white matter demyelination on mood regulation in elders who experienced the first depressive episode. More recently, the chronic accumulation of lacunes in thalamus, basal ganglia and deep white matter has been considered as a strong correlate of PSD. We provide here a critical overview of neuroimaging and neuropathological sets of evidence regarding the affective repercussions of vascular burden in the aging brain and discuss their conceptual and methodological limitations. Based on these observations, we propose that the accumulation of small vascular and microvascular lesions constitutes a common neuropathological platform for both cognitive decline and depressive episodes in old age.

Diffusion tensor changes in patients with amnesic mild cognitive impairment and various dementias

White matter damage and its contribution to clinical manifestations in patients with dementia have been increasingly recognized. To explore white matter changes in different types of dementia, we examined brain water diffusivity with diffusion tensor imaging (DTI). We measured fractional anisotropy and mean diffusivity of multiple white matter regions in patients with amnesic mild cognitive impairment (MCI, n=10), Alzheimer's disease (AD, n=30), subcortical ischemic vascular dementia (SIVD, n=18), frontotemporal dementia (FTD, n=7), and control subjects (n=20). We performed pairwise comparisons in each region of interest between patients and controls. MCI patients showed diffusion tensor change (DTC) in the left anterior periventricular (PV) area, possibly in the right posterior PV area, and the genu of the corpus callosum. AD patients showed DTC in the corpus callosum, and in frontal and parieto-occipital subcortical and anterior PV areas. In SIVD patients, DTC occurred in the genu of the corpus callosum, and in bilateral frontal subcortical and PV areas. FTD patients differed from controls in showing DTC in the temporal and frontal subcortical areas, the genu of the corpus callosum and PV areas. The degree of DTC correlated with the clinical severity of dementia as assessed by the clinical dementia rating (CDR). Mean diffusivity was diffusely and positively associated with the CDR scores. Fractional anisotropy of the PV areas was negatively associated with the CDR scores, suggesting a critical role of the lateral cholinergic pathways.

White Matter Integrity and Episodic Memory Performance in Mild Cognitive Impairment: A Diffusion Tensor Imaging Study

White matter (WM) integrity in the medial temporal lobes and episodic memory performance was examined in patients with mild cognitive impairment (MCI) and age-matched cognitively intact controls. Material specific associations between WM in the left versus right hemisphere and verbal versus visual memory performance were examined as well. Fourteen right-handed amnestic MCI patients underwent diffusion tensor imaging (DTI) and received verbal (words, story) and visual (designs) memory tests. Delayed verbal memory was significantly correlated with loss of WM integrity in the medial temporal lobe. This finding was associated with both the left and right temporal regions. Immediate visual memory performance was significantly correlated with the loss of WM integrity in the left temporal region. The results indicate that WM integrity in the medial temporal lobe is associated with objective memory functioning in MCI. However, strong material specific relationships were not observed, possibly reflecting diverse encoding strategies used by participants such as imagery of verbal material and verbal encoding of designs.

Measuring cerebral atrophy and white matter hyperintensity burden to predict the rate of cognitive decline in Alzheimer disease

OBJECTIVE

To determine if baseline measurements of cerebral atrophy and severity of white matter hyperintensity (WMH) predict the rate of future cognitive decline in patients with Alzheimer disease (AD).

DESIGN

Data were drawn from the Predictors Study, a longitudinal study that enrolls patients with mild AD and reassesses them every 6 months with use of the Columbia modified Mini-Mental State (mMMS) examination (score range, 0-57). Magnetic resonance images were analyzed to determine the severity of WMH, using the Scheltens scale, and the degree of atrophy, using the bicaudate ratio. Generalized estimating equations were used to determine whether severity of baseline magnetic resonance image measurements and their interaction predicted the rate of mMMS score decline at subsequent visits.

SETTING

Three university-based AD centers in the United States.

PARTICIPANTS

At baseline, 84 patients with AD from the Predictors Study received structural magnetic resonance imaging and were selected for analysis. They had a mean of 6 follow-up evaluations. Main Outcome Measure The mMMS score.

RESULTS

Generalized estimating equation models demonstrated that the degree of baseline atrophy (beta = -0.316; P = .04), the severity of WMH (beta = -0.173; P = .03), and their interaction (beta = -6.061; P = .02) predicted the rate of decline in mMMS scores.

CONCLUSIONS

Both degree of cerebral atrophy and severity of WMH are associated with the rapidity of cognitive decline in AD. Atrophy and WMH may have a synergistic effect on future decline in AD, such that patients with a high degree of both have a particularly precipitous cognitive course. These findings lend further support to the hypothesis that cerebrovascular pathological abnormalities contribute to the clinical syndrome of AD.

Classification of white matter lesions on magnetic resonance imaging in elderly persons

White matter lesions, commonly seen on MRIs of elderly people, are related to various geriatric disorders, including cerebrovascular diseases, cardiovascular diseases, dementia, and psychiatric disorders. Currently, white matter lesions are divided into periventricular white matter lesions and deep white matter lesions. Although the meaning of these terms varies by study and this dichotomization itself is still in debate, a possible dissimilarity in pathogenic mechanisms between periventricular white matter lesions and deep white matter lesions are providing some clues for understanding pathophysiology of many geriatric syndromes associated with white matter lesions. We have reviewed the distinctions between periventricular white matter lesions and deep white matter lesions in terms of etiology, histopathology, functional correlates, and imaging methodologies. We suggest a new subclassification of white matter lesions that might have better etiological and functional relevance than the current simple dichotomization. The new categories are juxtaventricular, periventricular, deep white, and juxtacortical. This new classification scheme might contribute to reducing the heterogeneity of white matter lesion findings in future research.

Neuroimaging and APOE genotype: a systematic qualitative review

Apolipoprotein E (APOE) is the major genetic risk factor for late-onset Alzheimer's disease (AD) and has also been implicated in cardiovascular disease, cognitive decline and cognitive changes in healthy ageing. The aim of this paper is to systematically review and critically assess the association between the APOE genotype and structural/functional cerebral changes as evidenced by brain imaging studies. A second aim is to determine whether these observed associations between APOE and the brain reflect changes which are consistent with the progression of AD neurodegenerative changes described in Braak stages. A search of Pubmed, Psycinfo, and Web of Science databases identified 64 articles available for qualitative review. The review found that presence of the APOE epsilon4 allele is associated with (1) hippocampal, amygdalar and entorhinal cortex atrophy, (2) increased brain atrophy, (3) increased white matter hyperintensity volumes and (4) altered cerebral blood flow and glucose metabolism patterns. It is possible that there are critical age ranges when these effects are evident and that the APOE epsilon2 genotype might present a risk. We conclude that structural brain change is associated with the APOE genotype and that it is more salient in younger ageing individuals.

Diffusion tensor imaging of normal-appearing white matter in mild cognitive impairment and early Alzheimer disease: preliminary evidence of axonal degeneration in the temporal lobe

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) is a sensitive technique for studying cerebral white matter. We used DTI to characterize microstructural white matter changes and their associations with cognitive dysfunction in Alzheimer disease (AD) and mild cognitive impairment (MCI).

MATERIALS AND METHODS

We studied elderly subjects with mild AD (n = 6), MCI (n = 11), or normal cognition (n = 8). A standardized clinical and neuropsychological evaluation was conducted on each subject. DTI images were acquired, and fractional anisotropy (FA), axial diffusivity (DA), and radial diffusivity (DR) of normal-appearing white matter (NAWM) in frontal, temporal, parietal, and occipital lobes were determined. These diffusion measurements were compared across the 3 groups, and significant differences were further examined for correlations with tests of cognitive function.

RESULTS

Compared with normal controls, AD subjects demonstrated decreased FA and increased DR in the temporal, parietal, and frontal NAWM and decreased DA in temporal NAWM. MCI subjects also showed decreased FA and decreased DA in temporal NAWM, with decreased FA and increased DR in parietal NAWM. Diffusion measurements showed no differences in occipital NAWM. Across all subjects, temporal lobe FA and DR correlated with episodic memory, frontal FA and DR correlated with executive function, and parietal DR significantly correlated with visuospatial ability.

CONCLUSIONS

We found evidence for functionally relevant microstructural changes in the NAWM of patients with AD and MCI. These changes were present in brain regions serving higher cortical functions, but not in regions serving primary functions, and are consistent with a hypothesized loss of axonal processes in the temporal lobe.

The relation between white-matter lesions and cognition

PURPOSE OF REVIEW

To summarize recent findings and developments in the field of the relation between white-matter lesions and cognition.

RECENT FINDINGS

Recent studies have provided further evidence that white-matter lesions exert a detrimental effect on cognitive profile. New magnetic-resonance techniques may help in clarifying the meaning and extent of this effect. Evidence is also increasing about lesion progression occurring over time, at least in patients with severe white-matter lesions, and this progression is one of the factors related to cognitive decline in the elderly. The need to delay or halt the progression of white-matter lesions has led to clarification of the role of some risk factors and to performance of therapeutic trials where white-matter lesions are used as a surrogate marker for the end point of small-vessel disease. In addition to cognitive effects, white-matter lesions have a role in the decline of other functional performances, and this places individuals with higher-grade lesions at increased risk of developing disability.

SUMMARY

White-matter lesions cannot be considered as mere incidental findings, at least in patients who show severe lesions. The pathogenesis of white-matter lesions must be clarified further and strategies found to delay their progression.

The enigma of vascular cognitive disorder and vascular dementia

The prevalence, morphology and pathogenesis of vascular dementia (VaD), recently termed vascular cognitive impairment, are a matter of discussion, and currently used clinical diagnostic criteria show moderate sensitivity (average 50%) and variable specificity (range 64-98%). In Western clinic-based series, VaD is suggested in 8-10% of cognitively impaired aged subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with reasonable values of 8-15%, while in Japan it is seen in 22-35%. Neuropathologic changes associated with cognitive impairment include multifocal and/or diffuse disease and focal lesions: multi-infarct encephalopathy, white matter lesions or arteriosclerotic subcortical (leuko)encephalopathy, multilacunar state, mixed cortico-subcortical type, borderline/watershed lesions, rare granular cortical atrophy, post-ischemic encephalopathy and hippocampal sclerosis. They result from systemic, cardiac and local large or small vessel disease. Recent data indicate that cognitive decline is commonly associated with widespread small ischemic/vascular lesions (microinfarcts, lacunes) throughout the brain with predominant involvement of subcortical and functionally important brain areas. Their pathogenesis is multifactorial, and their pathophysiology affects neuronal networks involved in cognition, memory, behavior and executive functioning. Vascular lesions often coexist with Alzheimer disease (AD) and other pathologies. Minor cerebrovascular lesions, except for severe amyloid angiopathy, appear not essential for cognitive decline in full-blown AD, while both mild Alzheimer pathology and small vessel disease may interact synergistically. The lesion pattern of "pure" VaD, related to arteriosclerosis and microangiopathies, differs from that in mixed-type dementia (AD with vascular encephalopathy), more often showing large infarcts, which suggests different pathogenesis of both types of lesions. Due to the high variability of cerebrovascular pathology and its causative factors, no validated neuropathologic criteria for VaD are available, and a large variability across laboratories still exists in the procedures for morphologic examination and histology techniques.

White matter lesions - age-adjusted values for cognitively healthy and demented subjects

OBJECTIVES

To develop age-adjusted norms for white matter lesions (WML) and to differentiate dementia from mild cognitive impairment and normal aging.

MATERIALS AND METHODS

240 patients underwent a comprehensive clinical, neuropsychological and MRI examination. A scale was developed quantify WML in anatomically defined regions by rating size and frequency. FLAIR sequences were used to determine a global and a frontal score. The scores were correlated with the psychometric test results and the final clinical diagnosis: cognitively normal (CN), mild cognitive impairment (MCI), Alzheimer's Disease (AD), vascular dementia (VD). Age-adjusted curves for WML scores were calculated by means of a non-parametic smoothing method.

RESULTS

WML scores of the whole cerebrum and the frontal lobe were significantly increased in vascular dementia as compared to CN, MCI and AD. Individual WML scores correlated significantly with age and neuropsychological test results. For the age range 55-72, the WML scores of VD were significantly different from those of CN, MCI and AD.

CONCLUSIONS

Age-corrected WML load was significantly higher in vascular dementia as compared to MCI, AD and cognitively normals over a wide age range.

Sorting out the clinical consequences of ischemic lesions in brain aging: a clinicopathological approach

BACKGROUND

Vascular lesions are particularly common in the aged brain. However, it is still unclear whether all such lesions affect cognition.

OBJECTIVES

To better explore relationships between specific characteristics of vascular lesions (type, size and location) and cognitive status.

METHODS

We performed a review of currently available neuroimaging and post-mortem studies taking into account several recent clinicopathological reports in elderly individuals with varying levels of cognitive impairment.

RESULTS

New data reveals the significant impact of cortical microinfarcts on intellectual function, in contrast to focal cortical and white matter gliosis which are not significantly associated with cognitive status. Structural neuroimaging studies show inconsistent data regarding the cognitive consequences of WML. Neuropathological analyses reveal that both periventricular and subcortical demyelination are associated with cognitive status in the absence of macrovascular pathology. When lacunes are present, these microvascular lesions have no independent effect on intellectual impairment. The relationship between lacunes and cognition is highly dependent on localization. Basal ganglia and thalamic lacunes correlate with cognitive decline but not lacunes in the frontal, temporal and parietal deep white matter.

CONCLUSION

Recent studies suggest that some cases of dementia might be misclassified: 1. Cases with typical Alzheimer course and moderate lacunes in subcortical white matter should probably be considered pure Alzheimer's disease. 2. The presence of microscopic infarcts can markedly impact cognition but is not detectable by currently available neuroimaging techniques and the vascular component of such mixed cases may go undiagnosed. The development of urgently needed new criteria for vascular dementia should take into account the relative contribution of various types of vascular lesions that can impact cognitive function.

Assessing the cognitive impact of Alzheimer disease pathology and vascular burden in the aging brain: the Geneva experience

The progressive development of Alzheimer disease (AD)-related lesions, such as neurofibrillary tangles (NFT), amyloid deposits and synaptic loss, and the occurrence of microvascular and small macrovascular pathology within the cerebral cortex are conspicuous neuropathologic features of brain aging. Recent neuropathologic studies strongly suggested that the clinical diagnosis of dementia depends more on the severity and topography of pathological changes than on the presence of a qualitative marker. However, several methodological problems, such as selection biases, case-control design, density-based measures and masking effects, of concomitant pathologies persisted. In recent years, we performed several clinicopathologic studies using stereological counting of AD lesions. In order to define the cognitive impact of lacunes and microvascular lesions, we also analyzed pure vascular cases without substantial AD pathology. Our data revealed that total NFT numbers in the CA1 field, cortical microinfarcts and subcortical gray matter lacunes were the stronger determinants of dementia. In contrast, the contribution of periventricular and subcortical white matter demyelinations had a modest cognitive effect even in rare cases with isolated microvascular pathology. Importantly, in cases with pure AD pathology, more than 50% of Clinical Dementia Rating scale variability was not explained by NFT, amyloid deposits and neuronal loss in the hippocampal formation. In cases with microvascular pathology or lacunes, this percentage was even lower. The present review summarizes our data in this field and discusses their relevance within the theoretical framework of the functional neuropathology of brain aging and with particular reference to the current efforts to develop standardized neuropathological criteria for mixed dementia.

The neurobiology of neuropsychiatric syndromes in dementia

PURPOSE OF REVIEW

Neuropsychiatric disturbances in dementia are prevalent, and research is uncovering their neurobiological correlates.

RECENT FINDINGS

Late-onset depression appears to be associated with Alzheimer's disease pathology at autopsy, and lifetime depression episodes may worsen Alzheimer's disease pathology in the hippocampus. Vascular disease and elevated homocysteine increase risk for both late-onset depression and Alzheimer's disease and may partly mediate their relationship. Monoamine changes are robust finding in Alzheimer's disease and may account for many observed depression symptoms. Risk of psychosis of Alzheimer's disease appears to be increased by several genes also implicated in schizophrenia (e.g., catechol-O-methyltransferase, neuregulin-1). Psychosis in dementia with Lewy bodies appears to be related to cholinergic deficits. Alzheimer's disease is associated with changes in the circadian sleep-wake cycles, including decreased night-time melatonin. Sleep apnea may be related to apolipoprotein E genotype and impact cognition in Alzheimer's disease. Rapid eye movement sleep behavior disorder is intricately related to synucleinopathies, such as dementia with Lewy bodies, but synuclein changes may not totally explain this relationship.

SUMMARY

Neuropsychiatric disturbances are a core feature of dementia and worsen many clinical outcomes. Among the most validated syndromes are depression, psychosis, and sleep disturbance of Alzheimer's disease. Neuropathology, neuroimaging, and genetic studies increasingly provide insight into the origins of these psychiatric symptoms in dementia.