Long-term risk of dementia following hospitalization due to physical diseases: A multicohort study

The Association of Thyroid Disease with Risk of Dementia and Cognitive Impairment: A Systematic Review

Background and Objectives: Cognitive impairment is defined as a reduced ability to perform one or more cognitive functions, potentially leading to dementia if the condition worsens. With dementia being a rapidly growing public health issue affecting approximately 50 million people worldwide, understanding modifiable risk factors such as thyroid disease is crucial for prevention and early diagnosis. Thyroid hormones play a vital role in brain development and functioning, impacting processes such as neuron growth, myelination, and neurotransmitter synthesis. Recent decades have seen thyroid disorders emerging as potential independent risk factors for reversible cognitive impairment. Materials and Methods: The review adheres to PRISMA guidelines, utilizing a structured PICO question to explore whether individuals with thyroid diseases have a higher risk of developing dementia and cognitive impairments compared to those without. The literature search was conducted in PubMed, Cochrane, and ScienceDirect databases, including studies published from 1 January 2019 to 31 December 2023. The literature review discusses nine selected articles. Results: The findings highlight a complex association between thyroid dysfunction and cognitive decline, with some studies indicating significant links, particularly with hypothyroidism, and others suggesting the relationship may depend on the specific type of thyroid dysfunction or cognitive domain affected. Six out of nine articles found a link between thyroid disease and cognitive impairment, while three articles refuted this link. Conclusions: The review reveals a complex and ambiguous relationship between thyroid dysfunction and cognitive impairment. Further research is needed to elucidate the mechanisms underlying these associations and to determine whether thyroid dysfunction may be a modifiable risk factor for dementia.

Thyroid dysfunction and risk of different types of dementia: A systematic review and meta-analysis

BACKGROUND

The impact of thyroid function on the risk of various types of dementia, including Alzheimer's disease (AD) and vascular dementia (VD), remains unclear. This meta-analysis investigates the association between thyroid dysfunction and the risk of these dementia types, aiming to inform strategies for dementia prevention.

METHODS

A comprehensive search was conducted in PubMed, Embase, and the Cochrane Library for studies published up to February 2023, focusing on the risk of thyroid dysfunction in dementia. We excluded duplicates, studies without full text, those with incomplete data, animal studies, case reports, and reviews. Data analysis was performed using STATA 15.1 software.

RESULTS

Our analysis indicated that overt hyperthyroidism significantly increases the risk of all studied dementia types (OR = 1.18, 95% CI: 1.04-1.35). In contrast, overt hypothyroidism was associated with a decreased risk of AD (OR = 0.73, 95% CI: 0.55-0.98) and VD (OR = 0.71, 95% CI: 0.62-0.82). Subclinical hyperthyroidism also showed a significant association with an increased risk of any dementia (OR = 1.26, 95% CI: 1.09-1.46) and specifically VD (OR = 6.70; 95% CI: 1.38-32.58).

CONCLUSION

This study suggests that overt hypothyroidism may reduce the risk of dementia, including AD and VD, whereas overt and subclinical hyperthyroidism are linked to an increased risk. These findings highlight the importance of monitoring thyroid function as a preventative measure against dementia.

Proteomics analysis of plasma from middle-aged adults identifies protein markers of dementia risk in later life

A diverse set of biological processes have been implicated in the pathophysiology of Alzheimer's disease (AD) and related dementias. However, there is limited understanding of the peripheral biological mechanisms relevant in the earliest phases of the disease. Here, we used a large-scale proteomics platform to examine the association of 4877 plasma proteins with 25-year dementia risk in 10,981 middle-aged adults. We found 32 dementia-associated plasma proteins that were involved in proteostasis, immunity, synaptic function, and extracellular matrix organization. We then replicated the association between 15 of these proteins and clinically relevant neurocognitive outcomes in two independent cohorts. We demonstrated that 12 of these 32 dementia-associated proteins were associated with cerebrospinal fluid (CSF) biomarkers of AD, neurodegeneration, or neuroinflammation. We found that eight of these candidate protein markers were abnormally expressed in human postmortem brain tissue from patients with AD, although some of the proteins that were most strongly associated with dementia risk, such as GDF15, were not detected in these brain tissue samples. Using network analyses, we found a protein signature for dementia risk that was characterized by dysregulation of specific immune and proteostasis/autophagy pathways in adults in midlife ~20 years before dementia onset, as well as abnormal coagulation and complement signaling ~10 years before dementia onset. Bidirectional two-sample Mendelian randomization genetically validated nine of our candidate proteins as markers of AD in midlife and inferred causality of SERPINA3 in AD pathogenesis. Last, we prioritized a set of candidate markers for AD and dementia risk prediction in midlife.

The role of peripheral inflammatory insults in Alzheimer's disease: a review and research roadmap

Peripheral inflammation, defined as inflammation that occurs outside the central nervous system, is an age-related phenomenon that has been identified as a risk factor for Alzheimer's disease. While the role of chronic peripheral inflammation has been well characterized in the context of dementia and other age-related conditions, less is known about the neurologic contribution of acute inflammatory insults that take place outside the central nervous system. Herein, we define acute inflammatory insults as an immune challenge in the form of pathogen exposure (e.g., viral infection) or tissue damage (e.g., surgery) that causes a large, yet time-limited, inflammatory response. We provide an overview of the clinical and translational research that has examined the connection between acute inflammatory insults and Alzheimer's disease, focusing on three categories of peripheral inflammatory insults that have received considerable attention in recent years: acute infection, critical illness, and surgery. Additionally, we review immune and neurobiological mechanisms which facilitate the neural response to acute inflammation and discuss the potential role of the blood-brain barrier and other components of the neuro-immune axis in Alzheimer's disease. After highlighting the knowledge gaps in this area of research, we propose a roadmap to address methodological challenges, suboptimal study design, and paucity of transdisciplinary research efforts that have thus far limited our understanding of how pathogen- and damage-mediated inflammatory insults may contribute to Alzheimer's disease. Finally, we discuss how therapeutic approaches designed to promote the resolution of inflammation may be used following acute inflammatory insults to preserve brain health and limit progression of neurodegenerative pathology.

Severe Infection and Risk of Cardiovascular Disease: A Multicohort Study

BACKGROUND

The excess risk of cardiovascular disease associated with a wide array of infectious diseases is unknown. We quantified the short- and long-term risk of major cardiovascular events in people with severe infection and estimated the population-attributable fraction.

METHODS

We analyzed data from 331 683 UK Biobank participants without cardiovascular disease at baseline (2006-2010) and replicated our main findings in an independent population from 3 prospective cohort studies comprising 271 329 community-dwelling participants from Finland (baseline 1986-2005). Cardiovascular risk factors were measured at baseline. We diagnosed infectious diseases (the exposure) and incident major cardiovascular events after infections, defined as myocardial infarction, cardiac death, or fatal or nonfatal stroke (the outcome) from linkage of participants to hospital and death registers. We computed adjusted hazard ratios (HRs) and 95% CIs for infectious diseases as short- and long-term risk factors for incident major cardiovascular events. We also calculated population-attributable fractions for long-term risk.

RESULTS

In the UK Biobank (mean follow-up, 11.6 years), 54 434 participants were hospitalized for an infection, and 11 649 had an incident major cardiovascular event at follow-up. Relative to participants with no record of infectious disease, those who were hospitalized experienced increased risk of major cardiovascular events, largely irrespective of the type of infection. This association was strongest during the first month after infection (HR, 7.87 [95% CI, 6.36-9.73]), but remained elevated during the entire follow-up (HR, 1.47 [95% CI, 1.40-1.54]). The findings were similar in the replication cohort (HR, 7.64 [95% CI, 5.82-10.03] during the first month; HR, 1.41 [95% CI, 1.34-1.48] during mean follow-up of 19.2 years). After controlling for traditional cardiovascular risk factors, the population-attributable fraction for severe infections and major cardiovascular events was 4.4% in the UK Biobank and 6.1% in the replication cohort.

CONCLUSIONS

Infections severe enough to require hospital treatment were associated with increased risks for major cardiovascular disease events immediately after hospitalization. A small excess risk was also observed in the long-term, but residual confounding cannot be excluded.

Association of blood pressure variability during acute care hospitalization and incident dementia

Background and objectives

Recognized as a potential risk factor for Alzheimer's disease and related dementias (ADRD), blood pressure variability (BPV) could be leveraged to facilitate identification of at-risk individuals at a population level. Granular BPV data are available during acute care hospitalization periods for potentially high-risk patients, but the incident ADRD risk association with BPV measured in this setting is unknown. Our objective was to evaluate the relation of BPV, measured during acute care hospitalization, and incidence of ADRD.

Methods

We retrospectively studied adults, without a prior ADRD diagnosis, who were admitted to a large quaternary care medical center in Southern California between January 1, 2013 and December 31, 2019. For all patients, determined BPV, calculated as variability independent of the mean (VIM), using blood pressure readings obtained as part of routine clinical care. We used multivariable Cox proportional hazards regression to examine the association between BP VIM during hospitalization and the development of incident dementia, determined by new ICD-9/10 coding or the new prescription of dementia medication, occurring at least 2 years after the index hospitalization.

Results

Of 81,892 adults hospitalized without a prior ADRD diagnosis, 2,442 (2.98%) went on to develop ADRD (2.6 to 5.2 years after hospitalization). In multivariable-adjusted Cox models, both systolic (HR 1.05, 95% CI 1.00-1.09) and diastolic (1.06, 1.02-1.10) VIM were associated with incident ADRD. In pre-specified stratified analyses, the VIM associations with incident ADRD were most pronounced in individuals over age 60 years and among those with renal disease or hypertension. Results were similar when repeated to include incident ADRD diagnoses made at least 1 or 3 years after index hospitalization.

Discussion

We found that measurements of BPV from acute care hospitalizations can be used to identify individuals at risk for developing a diagnosis of ADRD within approximately 5 years. Use of the readily accessible BPV measure may allow healthcare systems to risk stratify patients during periods of intense patient-provider interaction and, in turn, facilitate engagement in ADRD screening programs.

Hospitalizations in older-adults newly diagnosed with dementia: A population-based longitudinal study in Israel

OBJECTIVES

To compare inpatient burden (i.e. likelihood of hospitalization, number of admissions and length of stay) in persons with newly diagnosed dementia to the general population without dementia. Additionally, to evaluate whether inpatient burden is increased during the years prior to and post dementia diagnosis, and to identify factors associated with increased inpatient burden.

METHOD

The Israeli National Dementia Dataset (2016) was cross-linked with the National Hospital Discharge Database of the Israeli Ministry of Health (2014-2018). Dementia definition was based on documented dementia diagnoses and/or the purchase of medications during 2016. Mixed-effects models were applied to identify demographic and health characteristics associated with inpatient burden in the one and 2 years prior to and after dementia diagnosis.

RESULTS

The dataset included 11,625 individuals aged ≥65 years, identified as incident dementia cases. Compared to the general population of older-adults without dementia, those with newly diagnosed dementia had a higher age-standardized proportion of hospitalizations (26.4% vs. 40%). The odds for hospitalization were highest during the year preceding dementia diagnosis (OR = 3.19, 95% CI 2.51-4.06) compared to 2 years prior to diagnosis, and remained high (although slightly decreased) after dementia diagnosis. Older age was associated with inpatient burden after, but not prior to dementia diagnosis.

CONCLUSIONS

Older persons with dementia are a vulnerable population group with increased utilization of inpatient burden compared to those without dementia, particularly in the years surrounding dementia diagnosis. Sociodemographic risk factors may differ with respect to the time surrounding dementia diagnosis.

Association of Hypothyroidism and the Risk of Cognitive Dysfunction: A Meta-Analysis

Objectives: The purpose of this meta-analysis was to assess whether there is an association between hypothyroidism and the risk of cognitive dysfunction. Methods: PubMed, Cochrane Library, and Embase were searched for relevant studies published from database inception to 4 May 2022, using medical subject headings (MeSHs) and keywords. Results: Eight studies involving 1,092,025 individuals were included, published between 2010 and 2021. The pooled analysis showed that there was no association between hypothyroidism and cognitive dysfunction (OR = 1.13, 95% CI = 0.84−1.51, p = 0.426), including both all-cause dementia (OR = 1.04, 95% CI = 0.76−1.43, p = 0.809) and cognitive impairment (OR = 1.50, 95% CI = 0.68−3.35, p = 0.318). Neither overt hypothyroidism (OR = 1.19, 95% CI = 0.70−2.02, p = 0.525) nor subclinical hypothyroidism (OR = 1.04, 95% CI = 0.73−1.48, p = 0.833) was associated with cognitive dysfunction. Neither prospective cohort (OR = 1.08, 95% CI = 0.77−1.51, p = 0.673) nor cross-sectional studies (OR = 1.23, 95% CI = 0.63−2.42, p = 0.545) had any effect on the association. Interestingly, the risk of cognitive dysfunction was significantly increased in the group not adjusted for vascular comorbidity (OR = 1.47, 95% CI = 1.07−2.01, p = 0.017), while it was reduced in the adjusted group (OR =0.82, 95% CI = 0.79−0.85, p < 0.001). Conclusions: This meta-analysis shows that hypothyroidism was associated with a reduced risk of cognitive dysfunction after adjustment for vascular-disease comorbidities. More prospective observational studies are needed in the future to investigate the relationship between hypothyroidism and cognitive dysfunction.

Immune-mediated diseases are associated with a higher incidence of dementia: a prospective cohort study of 375,894 individuals

BACKGROUND

Immune system dysregulation plays a vital role in the pathogenesis of neurodegenerative diseases, even considered to be as important as classical pathological protein aggregation assumption. However, the associations of immune-mediated diseases with incident dementia are unclear and need to be clarified in prospective studies with a large population and long follow-up time.

METHODS

We investigated the relationship between any or individual immune-mediated diseases and incident dementia based on a prospective cohort UK Biobank. The risk for dementia was assessed with multivariable hazard ratio (HR) and 95% confidence interval (CI) after adjusting for various potential confounders using time-varying Cox proportional hazards regression. We also performed the subgroup Cox analysis stratified by time since immune-mediated diseases and gender. Causal mediation analyses with 1000 bootstrapped iterations were conducted to explore the mediation effects of peripheral immune cells on the associations of immune-mediated diseases with dementia.

RESULTS

A total of 375,894 participants were included in the study, among which 5291 developed dementia during a median follow-up of 9.08 years. Immune-mediated diseases were associated with an increased risk of dementia (HR, 1.10; 95% CI, 1.00-1.21), and the risk was highest between 1 and 2 years after immune-mediated diseases onset (HR, 2.74; 95% CI, 1.86-4.04). Females who suffered from immune-mediated diseases were more prone to AD, while males were more susceptible to VD. Four of the individual immune-mediated diseases including type I diabetes mellitus (HR, 2.49; 95% CI, 1.97-3.15), rheumatic fever or rheumatic heart diseases (HR, 1.36; 95% CI, 1.05-1.77), multiple sclerosis (HR, 2.87; 95% CI, 1.92-4.30), and necrotizing vasculopathies (HR, 1.71; 95%CI, 1.03-2.85) were significantly related to higher dementia incidence. The relationship between immune-mediated diseases and dementia was partially mediated by peripheral immune cells including neutrophils and lymphocytes.

CONCLUSIONS

In this large cohort study, immune-mediated diseases were proven to be significantly associated with an increased risk of incident dementia, especially for type I diabetes mellitus which was observed to be related to the higher incidence of all types of dementia. Our findings could provide new sights on dementia pathogenesis and intervention from the perspective of systemic immunology and immune-mediated diseases.

Plasma proteins, cognitive decline, and 20-year risk of dementia in the Whitehall II and Atherosclerosis Risk in Communities studies

INTRODUCTION

Plasma proteins affect biological processes and are common drug targets but their role in the development of Alzheimer's disease and related dementias remains unclear. We examined associations between 4953 plasma proteins and cognitive decline and risk of dementia in two cohort studies with 20-year follow-ups.

METHODS

In the Whitehall II prospective cohort study proteins were measured using SOMAscan technology. Cognitive performance was tested five times over 20 years. Linkage to electronic health records identified incident dementia. The results were replicated in the Atherosclerosis Risk in Communities (ARIC) study.

RESULTS

Fifteen non-amyloid/non-tau-related proteins were associated with cognitive decline and dementia, were consistently identified in both cohorts, and were not explained by known dementia risk factors. Levels of six of the proteins are modifiable by currently approved medications for other conditions.

DISCUSSION

This study identified several plasma proteins in dementia-free people that are associated with long-term risk of cognitive decline and dementia.

Association of a wide range of chronic diseases and apolipoprotein E4 genotype with subsequent risk of dementia in community-dwelling adults: A retrospective cohort study

Background

Identifying independent and interactive associations of a wide range of diseases and multimorbidity and apolipoprotein E4 (APOE4) with dementia may help promote cognitive health. The main aim of the present study was to investigate associations of such diseases and their multimorbidity with incident dementia.

Methods

In this retrospective cohort study, we included 471,485 individuals of European ancestry from the UK Biobank, aged 38-73 years at baseline (2006-10). Dementia was identified using inpatient records and death registers. The follow-up period was between March 16, 2006, and Jan 31, 2021.

Findings

During a median follow-up of 11·9 years, 6189 cases of incident all-cause dementia (503 young-onset cases, 5686 late-onset cases) were documented. In multivariable-adjusted analysis, 33 out of 63 major diseases were associated with an increased risk of dementia. The hazard ratio (HR [95% CI]) ranged from 1·12 (1·06-1·19) for obesity to 14·22 (12·33-16·18) for Parkinson's disease. In addition to conventional diseases, respiratory disorders, musculoskeletal disorders, digestive disorders, painful conditions, and chronic kidney disease were associated with increased dementia risk. A larger HR for dementia was observed for a larger number of diseases (3·97 [3·51-4·48] for ≥6 diseases versus no disease). These individual diseases and multimorbidity were more predictive of young-onset dementia than of late-onset dementia. Dementia risk score incorporating multimorbidity, age, and APOE4 status had strong prediction performance (area under the curve [95% CI]: 82·2% [81·7-82·7%]). APOE4 was more predictive of late-onset dementia (HR [95% CI]: 2·90 [2·75-3·06]) than of young-onset dementia (1·26 [1·03-1·54]). Associations of painful conditions, depression, obesity, diabetes, stroke, Parkinson's disease, high cholesterol, and their multimorbidity with incident dementia were stronger among non-APOE4 carriers.

Interpretation

Besides conventional diseases, numerous diseases are associated with an increased risk of dementia. These individual diseases and multimorbidity are more predictive of young-onset dementia, whereas APOE4 is more predictive of late-onset dementia. Individual diseases and multimorbidity are stronger predictors of dementia in non-APOE4 carriers. Although multiple risk factors have been adjusted for in the analysis, potential confounding from unknown factors may have biased the associations.

Funding

The Fundamental Research Funds of the State Key Laboratory of Ophthalmology, Project of Investigation on Health Status of Employees in Financial Industry in Guangzhou, China (Z012014075), Science and Technology Program of Guangzhou, China (202,002,020,049).