Dementia is a frequent problem encountered in advanced stages of Parkinson disease (PD). In recent years, research has focused on the pre-dementia stages of cognitive impairment in PD, including mild cognitive impairment (MCI). Several longitudinal studies have shown that MCI is a harbinger of dementia in PD, although the course is variable, and stabilization of cognition — or even reversal to normal cognition — is not uncommon. In addition to limbic and cortical spread of Lewy pathology, several other mechanisms are likely to contribute to cognitive decline in PD, and a variety of biomarker studies, some using novel structural and functional imaging techniques, have documented in vivo brain changes associated with cognitive impairment. The evidence consistently suggests that low cerebrospinal fluid levels of amyloid-β42, a marker of comorbid Alzheimer disease (AD), predict future cognitive decline and dementia in PD. Emerging genetic evidence indicates that in addition to the APOE*ε4 allele (an established risk factor for AD), GBA mutations and SCNA mutations and triplications are associated with cognitive decline in PD, whereas the findings are mixed for MAPT polymorphisms. Cognitive enhancing medications have some effect in PD dementia, but no convincing evidence that progression from MCI to dementia can be delayed or prevented is available, although cognitive training has shown promising results.

In 2007, the clinical and research profile of illusions, hallucinations, delusions and related symptoms in Parkinson disease (PD) was raised with the publication of a consensus definition of PD psychosis. Symptoms that were previously deemed benign and clinically insignificant were incorporated into a continuum of severity, leading to the rapid expansion of literature focusing on clinical aspects, mechanisms and treatment. Here, we review this literature and the evolving view of PD psychosis. Key topics include the prospective risk of dementia in individuals with PD psychosis, and the causal and modifying effects of PD medication. We discuss recent developments, including recognition of an increase in the prevalence of psychosis with disease duration, addition of new visual symptoms to the psychosis continuum, and identification of frontal executive, visual perceptual and memory dysfunction at different disease stages. In addition, we highlight novel risk factors — for example, autonomic dysfunction — that have emerged from prospective studies, structural MRI evidence of frontal, parietal, occipital and hippocampal involvement, and approval of pimavanserin for the treatment of PD psychosis. The accumulating evidence raises novel questions and directions for future research to explore the clinical management and biomarker potential of PD psychosis.

The CogTrack TM System is proprietary to Wesnes Cognition Ltd (www.wesnes.com). Keith Wesnes owns Wesnes Cognition Ltd and consults for various companies involved in clinical trials. Helen Brooker is employed by Wesnes Cognition Ltd. Clive

Objective: Loneliness and physical activity are important targets for research into the impact of COVID-19 because they have established links with mental health, could be exacerbated by social distancing policies and are potentially modifiable. In this study we aimed to identify whether loneliness and physical activity were associated with worse mental health during a period of mandatory social distancing in the UK. Design: Population-based observation cohort study. Setting: Mental health data collected online during COVID-19 from an existing sample of adults aged 50 and over taking part in a longitudinal study of ageing. All had comparable annual data collected between 2015 and 2019. Participants: 3,281 participants aged 50 and over. Measurements: Trajectories of depression (measured by PHQ-9) and anxiety (measured by GAD-7) between 2015 and 2020 were analyzed with respect to loneliness, physical activity levels and a number of socioeconomic and demographic characteristics using zero-inflated negative binomial regression. Results: In 2020, PHQ-9 score for loneliness, adjusted for covariates, was 3.23 (95% CI: 3.01-3.44), an increase of around one point on all previous years in this group and 2 points higher than people not rated lonely, whose score did not change in 2020 (1.22, 95% CI: 1.12-1.32). PHQ-9 was 2.60, 95% CI: 2.43-2.78 in people with decreased physical activity, an increase of 0.5 on previous years. In contrast, PHQ-9 in 2020 for people whose physical activity had not decreased was 1.66, 95% CI: 1.56-1.75, similar to previous years. A similar relationship was observed for GAD-7 though the absolute burden of symptoms lower. Conclusion: After accounting for pre-COVID-19 trends, we show that experiencing loneliness and decreased physical activity are risk factors for worsening mental health during the pandemic. Our findings highlight the need to examine policies which target these potentially modifiable risk factors.

Atypical antipsychotics confer modest benefits for short-term (up to 12 weeks) treatment of aggression and psychosis in AD. These benefits have to be balanced against the risk of serious adverse events including 1.5 - 1.8-fold increased mortality. The benefits are less clear-cut with longer term prescribing, but the mortality risk remains significantly elevated. Pharmacogenetics may provide an opportunity to more effectively focus prescribing in the future.

ABSTRACTObjectives:In this large population study, we set out to examine the profile of mild behavioral impairment (MBI) by using the Mild Behavioral Impairment Checklist (MBI-C) and to explore its factor structure when employed as a self-reported and informant-rated tool.Design:This was a population-based cohort study.Setting:Participants were recruited from the Platform for Research Online to Investigate Genetics and Cognition in Aging study (https://www.protect-exeter.org.uk).Participants:A total of 5,742 participant-informant dyads participated in the study.Measurements:Both participants and informants completed the MBI-C. The factor structure of the MBI-C was evaluated by exploratory factor analysis.Results:The most common MBI-C items, as rated by self-reported and informants, related to affective dysregulation (mood/anxiety symptoms), being present in 34% and 38% of the sample, respectively. The least common items were those relating to abnormal thoughts and perception (psychotic symptoms) (present in 3% and 6% of the sample, respectively). Only weak correlations were observed between self-reported and informant-reported MBI-C responses. Exploratory factor analysis for both sets of respondent answers indicated that a five-factor solution for the MBI-C was appropriate, reflecting the hypothesized structure of the MBI-C.Conclusion:This is the largest and most detailed report on the frequency of MBI symptoms in a nondementia sample. The full spectrum of MBI symptoms was present in our sample, whether rated by self-reported or informant report. However, we show that the MBI-C performs differently in self-reported versus informant-reported situations, which may have important implications for the use of the questionnaire in clinic and research.

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Background: Psychotic symptoms are common in Alzheimer's disease (AD) and related neurodegenerative disorders and are associated with more rapid disease progression and increased mortality. It is unclear to what degree existing criteria are utilized in clinical research and practice. Objective: To establish research criteria for the diagnosis of psychosis in AD. Methods: The International Society to Advance Alzheimer's Research and Treatment (ISTAART) Neuropsychiatric Symptoms (NPS) Professional Interest Area (PIA) psychosis subgroup reviewed existing criteria for psychosis in AD and related dementias. Through a series of in person and on-line meetings, a priority checklist was devised to capture features necessary for current research and clinical needs. PubMed, Medline and other relevant databases were searched for relevant criteria. Results: Consensus identified three sets of criteria suitable for review including those of Jeste and Finkel, Lyketsos, and the Diagnostic and Statistical Manual for Mental Disorders, 5th edition. It was concluded that existing criteria could be augmented by including a more specific differentiation between delusions and hallucinations, address overlap with related conditions (agitation in particular), adding the possibility of symptoms emerging in the preclinical and prodromal phases, and building on developing research in disease biomarkers. Conclusion: We propose criteria, developed to improve phenotypic classification of psychosis in AD, and advance the research agenda in the field to improve epidemiological, biomarker, and genetics research in the field. These criteria serve as a complement to the International Psychogeriatric Association criteria for psychosis in neurocognitive disorders.