Infectious diseases and cognition: do we have to worry?

Cognitive impairment and dementia-Are they linked to childhood health and socioeconomic status? A systematic review

BACKGROUND

Dementia is a major public health concern, with its incidence rising as the population ages. Recent studies suggest links between childhood health, socioeconomic status, and later-life cognitive impairment and dementia, though findings remain inconclusive. This systematic review evaluates the influence of childhood health and socioeconomic status on cognitive impairment and dementia.

METHOD AND FINDINGS

A systematic search conducted in MEDLINE, CiNAHL, and PsycINFO in December 2024 identified 44 studies matching our inclusion criteria. Findings are presented under five key themes: (1) childhood health, (2) childhood educational attainment, (3) family socioeconomic and educational factors, (4) childhood experiences, and (5) childhood reading habits and social interactions.

CONCLUSION

Our results highlight the need for further longitudinal studies to establish causal relationships between early-life risk factors and later cognitive decline. Policymakers should prioritize early childhood development programs that integrate health, nutrition, education, and social support to help mitigate cognitive impairment and dementia in later life.

SARS-CoV-2: A synergy to the Alzheimer's disease

COVID-19 was a nightmare in humankind's history that challenged our advanced medical technology. All credit goes to the researchers who played a crucial role in curbing COVID-19 and proved our medical technology supremacy. However, COVID-19 has left some mysterious scars on human well-being. It is believed that COVID-19 has a significant negative impact on various cardiovascular (CVS) and central nervous system (CNS) diseases, especially in the case of CNS diseases like Alzheimer's. Surprisingly, COVID-19 affects the respiratory system, whereas Alzheimer's disease (AD) alters brain function. To explain this phenomenon, several hypotheses were proposed, but the mechanism needs to be clearly understood. Another critical thing to be concerned about is that COVID-19 will worsen pre-existing conditions and lead to the onset of AD. In the race to curb COVID-19, the invention of vaccines was speeded up, and it is necessary to fight against COVID-19. However, postvaccination follow-up is mandatory when an individual is a victim of AD. In this review article, we compiled the various dreadful effects of the COVID-19 virus on AD, the Post effects of the virus on AD, and the effect of the COVID-19 vaccination on AD. This article provides a new direction for research concerning COVID-19 and AD.

Results of a Codesign Process: A Cognition Screening Pathway for Inpatient and Outpatient Settings for Patients Who Are Facing or Have Undergone Lower Limb Amputation

Background/Objectives: Cognition plays a major role in prosthetic rehabilitation success. The ability to identify patients who may have difficulty understanding and adapting to the rehabilitation process is beneficial for clinicians and patients to allow for targeted and appropriate therapy. The research aim was to codesign a process that facilitates routine cognitive screening into the amputee inpatient journey. Methods: A convenience sample of sixteen medical and allied health practitioners from one local health district undertook a codesign process over 10 months from March to November 2023. A combination of virtual and face-to-face data collection occurred. Each of the codesign meetings was audio recorded, following which transcription occurred. Transcripts were reviewed using thematic analysis-based techniques to capture themes and consensus within the group. Results: Two pathways were established for use within one local health district, allowing clinicians to measure the cognition of patients in both inpatient and outpatient settings either before or after they underwent amputation. The newly established pathways provide step-by-step guidance for clinicians, such as how to address contraindicators for testing and providing guidance for subsequent neuropsychological testing. The Montreal Cognitive Assessment (MoCA), both paper based and electronic based, was selected as the cognitive screening tool for implementation. Conclusions: Utilizing codesign as a method for generating a cognitive screening pathway for amputees was successful. The pathways generated should be reviewed for suitability for application in other health settings.

RSV vaccination as the optimal prevention strategy for older adults

Respiratory syncytial virus (RSV) is a respiratory virus that usually causes mild upper respiratory tract symptoms. However, it can lead to a severe lower respiratory tract disease in high-risk populations, with severe complications such as pneumonia and respiratory failure. RSV poses a significant public health threat not only to children, but also to adults, particularly those over 75 years of age and individuals with comorbidities. The high incidence and severity of RSV infections in these vulnerable groups highlights the urgent need for effective preventive strategies. Despite advancements in the clinical management of respiratory infections, preventing RSV remains a significant challenge. The symptoms of RSV are often underestimated and misdiagnosed due to their similarity to other respiratory infections like influenza and COVID-19. This leads to a substantial disease burden not only for patients but also for healthcare systems, due to increased hospitalizations and prolonged treatments. In recent years, there has been a significant progress in the development of RSV vaccines, offering new hope for disease prevention. Our aim is to promote RSV vaccination, emphasizing the importance of large-scale prevention efforts to enhance the quality of life for at-risk individuals and optimize healthcare resource allocation. This paper will report efficacy and safety data for the three main vaccines currently available for healthcare practitioners, providing a comprehensive and balanced overview of vaccine options and supporting informed decision-making by healthcare professionals and regulatory authorities.

Assessment of Inflammatory Scores in Severity Prediction for Elderly Patients with Odontogenic Infections

Background and Objectives: Odontogenic infections (OIs) can lead to severe complications, especially in elderly patients due to age-related physiological changes and comorbidities. This study aims to evaluate the predictive accuracy of inflammatory scores-APACHE II, CURB-65, SOFA, and NEWS2-in determining the severity of odontogenic infections among elderly patients (>70 years) compared to younger patients (<70 years). Materials and Methods: A retrospective cohort study was conducted on patients diagnosed with an OI at the Maxillofacial Surgery Department between January 2018 and January 2024. Patients were divided into two groups: elderly patients (>70 years, n = 49) and younger patients (<70 years, n = 64). The Symptom Severity score (SS) of odontogenic infections was calculated for all patients. Inflammatory scores-APACHE II, CURB-65, SOFA, and NEWS2-were assessed at admission and correlated with infection severity. Additional subgroup analyses were performed based on comorbidities and infection sites. Results: Elderly patients exhibited significantly higher SS scores (mean 12.47 ± 2.93) compared to younger patients (mean 7.82 ± 2.17, p < 0.001). APACHE II, CURB-65, SOFA and NEWS2 scores were significantly elevated in the elderly group (all p < 0.001). The SOFA score demonstrated the highest predictive accuracy for severe OIs in elderly patients, with an area under the curve (AUC) of 0.89 (95% CI: 0.82-0.95). Subgroup analyses revealed that comorbidities such as diabetes mellitus and cardiovascular disease significantly influenced infection severity (p < 0.05). Conclusions: Inflammatory scores, particularly SOFA, are effective in predicting the severity of odontogenic infections in elderly patients. The integration of these scores into clinical practice may enhance early identification of high-risk patients and improve management strategies.

The inter-relationship between Helicobacter pylori infection, dementia and mortality in type 2 diabetes: The Fremantle Diabetes Study Phase I

BACKGROUND

Given sparse relevant data, the aim of this study was to determine whether Helicobacter pylori infection, including cytotoxin-associated gene-A (CagA) producing strains, is associated with dementia in type 2 diabetes (T2DM).

METHODS

Longitudinal data from 1115 participants in the community-based Fremantle Diabetes Study Phase I (mean age 64.0 years, 48.0 % males; 38.0 % H. pylori seronegative, 24.3 % H. pylori seropositive/CagA seronegative, and 37.7 % H. pylori/CagA seropositive at baseline) were analyzed.

RESULTS

During up to 19 years of follow-up, 50.3 % and 83.5 % of participants without and with incident dementia, respectively, died. In Cox proportional hazards models, H. pylori/CagA seropositivity (hazard ratio (95 % CI) 1.68 (1.15, 2.46), P = 0.008), but not H. pylori seropositivity/CagA seronegativity (P = 0.541) was an independent predictor of incident dementia, but neither H. pylori seropositivity/CagA seronegativity nor H. pylori/CagA seropositivity were significant predictors in competing risks models (P ≥ 0.280).

CONCLUSIONS

Although CagA seropositivity in T2DM may have a contributory etiologic role in the risk of dementia, this may be through its association with reduced cardiovascular/all-cause mortality.

Plasma IL-6 levels and their association with brain health and dementia risk: A population-based cohort study

BACKGROUND

Recent studies have associated immune abnormalities with dementia. IL-6 is a crucial cytokine in inflammatory responses, and recent evidence has linked elevated IL-6 levels to changes in brain structure and cognitive decline. However, the connection between IL-6 levels, cognition, brain volumes, and dementia risk requires exploration in large prospective cohorts.

METHODS

This study utilized a longitudinal cohort from the UK Biobank to analyze the correlation between IL-6 expression levels, cognitive performance, and cortical and subcortical brain volumes through linear regression. Additionally, we assessed the association between IL-6 levels and long-term dementia risk using Cox regression analysis. We also used one-sample Mendelian randomization to analyze the impact of genetic predisposition of dementia on elevated IL-6 levels.

RESULTS

A total of 50,864 participants were included in this study, with 1,391 new cases of all-cause dementia identified. Higher plasma IL-6 levels are associated with cortical and subcortical atrophy in regions such as the fusiform, thalamus proper, hippocampus, and larger ventricle volumes. IL-6 levels are negatively associated with cognitive performance in pair matching, numeric memory, prospective memory, and reaction time tests. Furthermore, elevated IL-6 levels are linked to a 23-35 % increased risk of all-cause dementia over an average follow-up period of 13.2 years. The one-sample Mendelian randomization analysis did not show associations between the genetic predisposition of dementia and elevated IL-6 levels.

CONCLUSIONS

Increased IL-6 levels are associated with worse cognition, brain atrophy, and a heightened risk of all-cause dementia. Our study highlights the need to focus on the role of peripheral IL-6 levels in managing brain health and dementia risk.

Human Cytomegalovirus Infection and Neurocognitive and Neuropsychiatric Health

A common infection, human cytomegalovirus (HCMV) has been associated with a variety of human diseases, including cardiovascular disease and possibly certain cancers. HCMV has also been associated with cognitive, psychiatric, and neurological conditions. Children with congenital or early-life HCMV are at risk for microcephaly, cerebral palsy, and sensorineural hearing loss, although in many cases sensorineural loss may resolve. In addition, HCMV can be associated with neurodevelopmental impairment, which may improve with time. In young, middle-aged, and older adults, HCMV has been adversely associated with cognitive function in some but not in all studies. Research has linked HCMV to Alzheimer's and vascular dementia, but again not all findings consistently support these associations. In addition, HCMV has been associated with depressive disorder, bipolar disorder, anxiety, and autism-spectrum disorder, although the available findings are likewise inconsistent. Given associations between HCMV and a variety of neurocognitive and neuropsychiatric disorders, additional research investigating reasons for the considerable inconsistencies in the currently available findings is needed. Additional meta-analyses and more longitudinal studies are needed as well. Research into the effects of antiviral medication on cognitive and neurological outcomes and continued efforts in vaccine development have potential to lower the neurocognitive, neuropsychiatric, and neurological burden of HCMV infection.

Modelling lung infection with Klebsiella pneumoniae after murine traumatic brain injury

Pneumonia is a common comorbidity in patients with severe traumatic brain injury (TBI), and is associated with increased morbidity and mortality. In this study, we established a model of intratracheal Klebsiella pneumoniae administration in young adult male and female mice, at 4 days following an experimental TBI, to investigate how K. pneumoniae infection influences acute post-TBI outcomes. A dose-response curve determined the optimal dose of K. pneumoniae for inoculation (1 x 10^6 colony forming units), and administration at 4 days post-TBI resulted in transient body weight loss and sickness behaviors (hypoactivity and acute dyspnea). K. pneumoniae infection led to an increase in pro-inflammatory cytokines in serum and bronchoalveolar lavage fluid at 24 h post-infection, in both TBI and sham (uninjured) mice. By 7 days, when myeloperoxidase + neutrophil numbers had returned to baseline in all groups, lung histopathology was observed with an increase in airspace size in TBI + K. pneumoniae mice compared to TBI + vehicle mice. In the brain, increased neuroinflammatory gene expression was observed acutely in response to TBI, with an exacerbated increase in Ccl2 and Hmox1 in TBI + K. pneumoniae mice compared to either TBI or K. pneumoniae alone. However, the presence of neuroinflammatory immune cells in the injured brain, and the extent of damage to cortical and hippocampal brain tissue, was comparable between K. pneumoniae and vehicle-treated mice by 7 days. Examination of the fecal microbiome across a time course did not reveal any pronounced effects of either injury or K. pneumoniae on bacterial diversity or abundance. Together, these findings demonstrate that K. pneumoniae lung infection after TBI induces an acute and transient inflammatory response, primarily localized to the lungs with some systemic effects. However, this infection had minimal impact on secondary injury processes in the brain following TBI. Future studies are needed to evaluate the potential longer-term consequences of this dual-hit insult.

Viral Infections, Are They a Trigger and Risk Factor of Alzheimer's Disease?

Alzheimer's Disease (AD), a progressive and debilitating condition, is reported to be the most common type of dementia, with at least 55 million people believed to be currently affected. Many causation hypotheses of AD exist, yet the intriguing link between viral infection and its possible contribution to the known etiology of AD has become an attractive focal point of research for the field and a challenging study task. In this review, we will explore the historical perspective and milestones that led the field to investigate the viral connection to AD. Specifically, several viruses such as Herpes Simplex Virus 1 (HSV-1), Zika virus (ZIKV), and severe cute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with several others mentioned, include the various viruses presently considered within the field. We delve into the strong evidence implicating these viruses in the development of AD such as the lytic replication and axonal transport of HSV-1, the various mechanisms of ZIKV neurotropism through the human protein Musashi-1 (MSI1), and the spread of SARS-CoV-2 through the transfer of the virus through the BBB endothelial cells to glial cells and then to neurons via transsynaptic transfer. We will also explore beyond these mere associations by carefully analyzing the potential mechanisms by which these viruses may contribute to AD pathology. This includes but is not limited to direct neuronal infections, the dysregulation of immune responses, and the impact on protein processing (Aβ42 and hyperphosphorylated tau). Controversies and challenges of the virus-AD relationship emerge as we tease out these potential mechanisms. Looking forward, we emphasize future directions, such as distinct questions and proposed experimentations to explore, that the field should take to tackle the remaining unanswered questions and the glaring research gaps that persist. Overall, this review aims to provide a comprehensive survey of the past, present, and future of the potential link between viral infections and their association with AD development while encouraging further discussion.

Resolving a paradox: antidepressants, neuroinflammation, and neurodegeneration

Depression is a known risk factor for dementia. Antidepressants are the most commonly used treatment for this condition, and are effective in at least half to two-thirds of cases. Extensive evidence from in vitro and animal models suggests that antidepressants have anti-inflammatory and neuroprotective properties. These effects have been shown to reduce the oxidative damage, amyloid aggregation, and expression of pro-inflammatory genes associated with animal models of neurodegenerative disorders. However, longitudinal research in humans has shown that antidepressants do not protect against dementia, and may even be associated with a risk of cognitive deterioration over time in older adults. The contrast between two sets of findings represents a paradox of significant clinical and public health significance, particularly when treating depression in late life. This review paper attempts to resolve this paradox by critically reviewing the medium- and long-term effects of antidepressants on peripheral immune-inflammatory responses, infection risk, gut microbiota, and neuroendocrine responses to stress, and how these effects may influence the risk of neurodegeneration. Briefly stated, it is possible that the peripheral actions of antidepressant medications may antagonize their beneficial effects against neuroinflammation. The implications of these findings are then explored with a particular focus on the development and testing of multimodal neuroprotective and anti-inflammatory treatments that could reduce the risk of Alzheimer’s and related dementias in patients suffering from depression.

Association of Cognitive Impairment With Chronic Viral Hepatitis Among Older Adults in Taiwan

OBJECTIVE

To evaluate the risk of cognitive impairment among patients with chronic viral hepatitis.

DESIGN

A cross-sectional study.

SETTING

Population-based.

PARTICIPANTS

Individuals 60 years or older were enrolled from the Taiwan Biobank database from 2012.

EXPOSURE

Hepatitis B virus and hepatitis C virus infections.

MEASUREMENT

Cognitive impairment was evaluated using the mini-mental state examination (MMSE). Logistic regression models were used to calculate odds ratios and 95% confidence intervals (CIs). The effects of APOE ε4 polymorphisms on the association between viral hepatitis and the risk of cognitive impairment were also investigated.

RESULTS

We recruited 912 participants with cognitive impairment and 22 869 participants without cognitive impairment. The adjusted odds ratio (aOR) for cognitive impairment was 1.38 (95% CI: 1.03-1.85, p = 0.033) among participants with hepatitis C virus infection and 1.14 (95% CI: 0.91-1.43, p = 0.257) among participants with hepatitis B virus infection. Participants with hepatitis C virus infection and without hepatitis B virus infection had a higher risk of cognitive impairment (aOR: 1.52, 95% CI: 1.13-2.04, p = 0.006). The MMSE subcategories most associated with hepatitis C virus infection were orientation and design copying. The association between hepatitis C virus infection and cognitive impairment was higher among participants with ε4 alleles of the APOE gene than among those without alleles (aOR: 2.18, 95% CI: 1.21-3.91, p = 0.009).

CONCLUSIONS

Our findings suggest that individuals 60 years or older with chronic hepatitis C virus infection are at increased risk of cognitive impairment.

Short-term memory impairment following recovery from systemic inflammation induced by lipopolysaccharide in mice

The relationship between neuroinflammation and mental disorders has been recognized and investigated for over 30 years. Diseases of systemic or peripheral inflammation, such as sepsis, peritonitis, and infection, are associated with increased risk of mental disorders with neuroinflammation. To elucidate the pathogenesis, systemic administration of lipopolysaccharide (LPS) in mice is often used. LPS-injected mice exhibit behavioral abnormalities with glial activation. However, these studies are unlikely to recapitulate the clinical pathophysiology of human patients, as most studies focus on the acute inflammatory response with systemic symptoms occurring within 24 h of LPS injection. In this study, we focus on the effects of LPS on behavioral abnormalities following recovery from systemic symptoms and investigate the mechanisms of pathogenesis. Several behavioral tests were performed in LPS-injected mice, and to assess neuroinflammation, the time course of the morphological change and expression of inflammatory factors in neurons, astrocytes, and microglia were investigated. At 7 days post-LPS injection, mice exhibited short-term memory impairment accompanied by the suppression of neuronal activity and increases in morphologically immature spines. Glial cells were transiently activated in the hippocampus concomitant with upregulation of the microglial phagocytosis marker CD68 3 days after injection. Here we show that transient glial cell activation in the acute response phase affects neuronal activity and behavior following recovery from systemic symptoms. These findings provide novel insights for studies using the LPS-induced inflammation model and that will contribute to the development of treatments for mental disorders of this etiology.

Cognitive Performance in Asymptomatic Elderly People with Hepatitis C: The Role of Education

BACKGROUND

Neurotropism of the hepatitis C virus (HCV) can be the source of subtle neuropsychological symptoms in non-cirrhotic patients. Age is a risk factor for cognitive impairment (CI). Thus, asymptomatic elderly people who carry HCV might be at a greater risk of CI. Education can influence test performance.

OBJECTIVES

(1) To verify whether elderly people with HCV performed poorer than controls on cognitive tests. (2) To analyze how education affects performance. (3) To verify whether the extent of the effect of education on performance depends on the group (HCV vs. controls) and the type of cognitive test.

METHODS

Asymptomatic HCV carriers older than 60 years (n = 41) were matched with 41 corresponding controls. All participants performed the following tests: Mini-Cog, Mini Mental State Examination, clock drawing test (CDT), and verbal fluency.

RESULTS

(1) There were no significant differences in cognitive performance between the two groups. (2) Higher education was always associated with better performance. (3) There was a significant group difference in the slopes of the regression lines between years of education and CDT performance. No differences were found for the other three tests.

CONCLUSION

Considering the scores on the CDT, the rate of improvement in performance when schooling increases is higher in HCV carriers.

Biosafety and mental health: Virus induced cognitive decline

Biological agents threats people's life through different ways, one of which lies in the impairment of cognition. It is believed cognitive decline may result from biological agents mediated neuron damage directly, or from the activation of the host immune response to eradicate the pathogen. However, direct linkage between infections and cognitive decline is very limited. Here we focus on the mechanisms of how different biological virus or they induced systemic and local inflammation link to the cognitive impairment, focusing on the roles of activated microglia and several molecular pathways mediated neurotoxicity.

Health Care-Associated Infections in Older Adults: Epidemiology and Prevention

Health care-associated infections (HAIs) are a global public health threat, which disproportionately impact older adults. Host factors including aging-related changes, comorbidities, and geriatric syndromes, such as dementia and frailty, predispose older individuals to infection. The HAI risks from medical interventions such as device use, antibiotic use, and lapses in infection control follow older adults as they transfer among a network of interrelated acute and long-term care facilities. Long-term care facilities are caring for patients with increasingly complex needs, and the home-like communal environment of long-term care facilities creates distinct infection prevention challenges.

COVID-19 and Alzheimer's Disease: What Is the Connection?

Wang et al. found that elderly COVID-19 patients were at risk of AD. The following facts suggest a possible explanation: reactivation of herpes simplex virus type 1 (HSV1) and other herpesviruses can occur in SARS-CoV-2 patients; in cell cultures, HSV1 infection causes occurrence of many AD-like features, as does reactivation of latent HSV1 after addition of certain infectious agents; recurrent experimental reactivation of HSV1-infected mice leads to formation of the main features of AD brains, and to cognitive decline. These suggest that COVID-19 results in repeated reactivation of HSV1 in brain, with subsequent accumulation of damage and eventual development of AD.