The global burden of Alzheimer disease (AD), already the most common type of dementia, is expected to increase still further owing to population ageing. AD not only causes severe distress for patients and caregivers, but also results in a large economic burden on society. Current major challenges in AD include the lack of reliable biomarkers for its early diagnosis, as well as the lack of effective preventive strategies and treatments 1,2 . Thus, increased understanding of the molecular patho genesis of AD could lead to the development of improved diagnostic and therapeutic strategies.AD is conventionally regarded as a CNS disorder. However, increasing experimental, epidemiological and clinical evidence has suggested that manifestations of AD extend beyond the brain. These systemic alterations might not be simply secondary effects of the cerebral degeneration seen in AD, but could reflect under lying processes linked to progression of the disease. AD pathogenesis is complex, involving abnormal amyloid-β (Aβ) metabolism, tau hyperphosphorylation, oxidative stress, reactive glial and microglial changes, and other pathological events. Given that Aβ is a major hallmark of AD and a fertile area of research in this disease, this Review focuses on the systemic role of Aβ in AD. We discuss the communication between peripheral and central pools of Aβ, and describe interactions between systemic abnormalities and AD pathogenesis in the brain. We review emerging findings of associations between systemic abnormalities and Aβ metabolism, and describe how these associations might interact with or reflect on the central pathways of Aβ production and clearance. On the basis of these findings, we suggest that interactions between the brain and the periphery might have a crucial role in the development and progression of AD. Aβ biogenesis and catabolismA steady accrual of data from laboratories and clinics is providing increasing support for the concept that an imbalance between the production and clearance of Aβ is a very early (and often initiating) factor in AD 3 . Normal metabolism of Aβ and maintenance of the homeostatic balance between Aβ production and clearance is, therefore, essential to maintain brain health. In fact, physiological metabolism of Aβ occurs not only in the brain but also in the periphery, and communication between these regions is possible (FIG. 1). Central and peripheral production of AβAβ is derived from the proteolytic cleavage of amyloid precursor protein (APP), which is expressed not only in brain cells, including neurons, astrocytes and microglia, but also in peripheral organs and tissues, such as the Abstract | Alzheimer disease (AD) is the most common type of dementia, and is currently incurable; existing treatments for AD produce only a modest amelioration of symptoms. Research into this disease has conventionally focused on the CNS. However, several peripheral and systemic abnormalities are now understood to be linked to AD, and our understanding of how these alterations contribute to AD is becom...

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China bears a heavy burden of AD costs, which greatly change the estimates of AD cost worldwide.

BackgroundEvidence on preventing Alzheimer’s disease (AD) is challenging to interpret due to varying study designs with heterogeneous endpoints and credibility. We completed a systematic review and meta-analysis of current evidence with prospective designs to propose evidence-based suggestions on AD prevention.MethodsElectronic databases and relevant websites were searched from inception to 1 March 2019. Both observational prospective studies (OPSs) and randomised controlled trials (RCTs) were included. The multivariable-adjusted effect estimates were pooled by random-effects models, with credibility assessment according to its risk of bias, inconsistency and imprecision. Levels of evidence and classes of suggestions were summarised.ResultsA total of 44 676 reports were identified, and 243 OPSs and 153 RCTs were eligible for analysis after exclusion based on pre-decided criteria, from which 104 modifiable factors and 11 interventions were included in the meta-analyses. Twenty-one suggestions are proposed based on the consolidated evidence, with Class I suggestions targeting 19 factors: 10 with Level A strong evidence (education, cognitive activity, high body mass index in latelife, hyperhomocysteinaemia, depression, stress, diabetes, head trauma, hypertension in midlife and orthostatic hypotension) and 9 with Level B weaker evidence (obesity in midlife, weight loss in late life, physical exercise, smoking, sleep, cerebrovascular disease, frailty, atrial fibrillation and vitamin C). In contrast, two interventions are not recommended: oestrogen replacement therapy (Level A2) and acetylcholinesterase inhibitors (Level B).InterpretationEvidence-based suggestions are proposed, offering clinicians and stakeholders current guidance for the prevention of AD.

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IMPORTANCE Determining the long-term impact of COVID-19 on cognition is important to inform immediate steps in COVID-19 research and health policy.OBJECTIVE To investigate the 1-year trajectory of cognitive changes in older COVID-19 survivors.DESIGN, SETTING, AND PARTICIPANTS This cohort study recruited 3233 COVID-19 survivors 60 years and older who were discharged from 3 COVID-19-designated hospitals in Wuhan, China, from February 10 to April 10, 2020. Their uninfected spouses (N = 466) were recruited as a control population. Participants with preinfection cognitive impairment, a concomitant neurological disorder, or a family history of dementia were excluded, as well as those with severe cardiac, hepatic, or kidney disease or any kind of tumor. Follow-up monitoring cognitive functioning and decline took place at 6 and 12 months. A total of 1438 COVID-19 survivors and 438 control individuals were included in the final follow-up. COVID-19 was categorized as severe or nonsevere following the American Thoracic Society guidelines. MAIN OUTCOMES AND MEASURES The main outcome was change in cognition 1 year after patient discharge. Cognitive changes during the first and second 6-month follow-up periods were assessed using the Informant Questionnaire on Cognitive Decline in the Elderly and the Telephone Interview of Cognitive Status-40, respectively. Based on the cognitive changes observed during the 2 periods, cognitive trajectories were classified into 4 categories: stable cognition, early-onset cognitive decline, late-onset cognitive decline, and progressive cognitive decline. Multinomial and conditional logistical regression models were used to identify factors associated with risk of cognitive decline.RESULTS Among the 3233 COVID-19 survivors and 1317 uninfected spouses screened, 1438 participants who were treated for COVID-19 (691 male [48.05%] and 747 female [51.95%]; median [IQR] age, 69 [66-74] years) and 438 uninfected control individuals (222 male [50.68%] and 216 female [49.32%]; median [IQR] age, 67 [66-74] years) completed the 12-month follow-up. The incidence of cognitive impairment in survivors 12 months after discharge was 12.45%. Individuals with severe cases had lower Telephone Interview of Cognitive Status-40 scores than those with nonsevere cases and control individuals at 12 months (median [IQR]: severe, 22.50 [16.00-28.00]; nonsevere, 30.00 [26.00-33.00]; control , 31.00 [26.00-33.00]). Severe COVID-19 was associated with a higher risk of early-onset cognitive decline (odds ratio [OR], 4.87; 95% CI, 3.30-7.20), late-onset cognitive decline (OR, 7.58; 95% CI, 3.58-16.03), and progressive cognitive decline (OR, 19.00; 95% CI, 9.14-39.51), while nonsevere COVID-19 was associated with a higher risk of early-onset cognitive decline (OR, 1.71; 95% CI, 1.30-2.27) when adjusting for age, sex, education level, body mass index, and comorbidities. CONCLUSIONS AND RELEVANCEIn this cohort study, COVID-19 survival was associated with an increase in risk of longitudinal cognitive decline, highlighting the import...

Alzheimer’s disease (AD) is one of most devastating diseases affecting elderly people. Amyloid-β (Aβ) accumulation and the downstream pathological events such as oxidative stress play critical roles in pathogenesis of AD. Lessons from failures of current clinical trials suggest that targeting multiple key pathways of the AD pathogenesis is necessary to halt the disease progression. Here we show that Edaravone, a free radical scavenger that is marketed for acute ischemic stroke, has a potent capacity of inhibiting Aβ aggregation and attenuating Aβ-induced oxidation in vitro. When given before or after the onset of Aβ deposition via i.p. injection, Edaravone substantially reduces Aβ deposition, alleviates oxidative stress, attenuates the downstream pathologies including Tau hyperphosphorylation, glial activation, neuroinflammation, neuronal loss, synaptic dysfunction, and rescues the behavioral deficits of APPswe/PS1 mice. Oral administration of Edaravone also ameliorates the AD-like pathologies and memory deficits of the mice. These findings suggest that Edaravone holds a promise as a therapeutic agent for AD by targeting multiple key pathways of the disease pathogenesis.

smoking and drinking are risk factors for cognitive impairment among elderly people. Cessation of smoking and reduction of drinking could be considered as part of a strategy to reduce the incidence of cognitive impairment.