The epidemiology of Alzheimer's disease: laying the foundation for drug design, conduct, and analysis of clinical trials

Osteoporosis as a Potential Modifiable Risk Factor for Dementia in Thailand: A Cross-Sectional Analysis

OBJECTIVE

This study aims to explore the potential of osteoporosis as a modifiable risk factor for dementia and investigate whether treatments like estrogen supplementation and bisphosphonates can reduce the risk of dementia in the Thai population. This study aimed to evaluate the risk of dementia in patients with osteoporosis.

MATERIALS AND METHODS

A cross-sectional analysis was conducted. Participants aged <50 years and those with a history of dementia at baseline were excluded. Clinical variables were analyzed using the chi-squared test. Logistic regression analysis was conducted to determine independent factors of dementia after adjusting for potential confounders.

RESULTS

The cohort was conducted on 54,399 participants, of whom 9763 (17.9%) had osteoporosis. The results indicated that individuals with osteoporosis had an odds ratio (OR) of 1.62-fold higher risk of developing dementia compared to those without osteoporosis (95% confidence interval (CI) 1.37-1.92, p-value < 0.001). Furthermore, compared to patients with osteoporosis not undergoing any treatment, those receiving estrogen supplementation and bisphosphonate treatment showed reduced associations with dementia, with an OR of 0.84 (95% CI 0.73-0.98, p-value = 0.023) and 0.66 (95% CI 0.60-0.73, p-value < 0.001), respectively.

CONCLUSION

The study findings suggest an elevated risk of dementia in patients with osteoporosis and contribute substantially to our understanding of the link between osteoporosis and dementia in the Thai population.

Biomimetic Dendrimer-Peptide Conjugates for Early Multi-Target Therapy of Alzheimer's Disease by Inflammatory Microenvironment Modulation

Current therapeutic strategies for Alzheimer's disease (AD) treatments mainly focus on β-amyloid (Aβ) targeting. However, such therapeutic strategies have limited clinical outcomes due to the chronic and irreversible impairment of the nervous system in the late stage of AD. Recently, inflammatory responses, manifested in oxidative stress and glial cell activation, have been reported as hallmarks in the early stages of AD. Based on the crosstalk between inflammatory response and brain cells, a reactive oxygen species (ROS)-responsive dendrimer-peptide conjugate (APBP) is devised to target the AD microenvironment and inhibit inflammatory responses at an early stage. With the modification of the targeting peptide, this nanoconjugate can efficiently deliver peptides to the infected regions and restore the antioxidant ability of neurons by activating the nuclear factor (erythroid-derived 2)-like 2 signaling pathway. Moreover, this multi-target strategy exhibits a synergistic function of ROS scavenging, promoting Aβ phagocytosis, and normalizing the glial cell phenotype. As a result, the nanoconjugate can reduce ROS level, decrease Aβ burden, alleviate glial cell activation, and eventually enhance cognitive functions in APPswe/PSEN1dE9 model mice. These results indicate that APBP can be a promising candidate for the multi-target treatment of AD.

Voxel-Based Morphometry Reveals a Correlation Between Bone Mineral Density Loss and Reduced Cortical Gray Matter Volume in Alzheimer's Disease

Background: Decreased bone mineral density (BMD) was associated with poorer cognitive function and increased risk of Alzheimer's disease (AD). However, objective evidence for the relationship between osteoporosis and AD in humans has not been extensively described. Objectives: We aimed to evaluate the relationships between BMD and the cortical volumes of brain regions vulnerable to AD; hippocampus, parahippocampal gyrus, precuneus, posterior cingulate, and angular gyrus, using voxel-based morphometry (VBM), to investigate the association between bone loss and AD. Methods: A cohort of 149 consecutive elderly participants who complained of memory disturbance underwent high-resolution structural brain magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA). We used SPM12 software to conduct a voxel-based multiple regression analysis to examine the association between femoral neck BMD values and regional gray matter volume (rGMV) on structural T1-weighted MRI. Results: After adjusting for subject age, gender, total brain volume (TBV), and mini-mental state examination (MMSE) scores, the multiple regression analysis showed significant correlations between BMD loss and rGMV decline in the left precuneus, which is an important neural network hub vulnerable to AD. Conclusion: These data suggest that the bone and brain communicate with each other, as in "bone-brain crosstalk," and that control of BMD factors could contribute to cognitive function and help prevent AD.

Retinal nerve fiber layer thickness is associated with hippocampus and lingual gyrus volumes in nondemented older adults

OBJECTIVES

Abnormal retina structures, such as thinner retinal nerve fiber layer (RNFL), have been frequently reported in patients with Alzheimer's disease (AD). However, the association between RNFL and brain structures in cognitively normal adults remains unknown. We therefore set out to conduct a cross-sectional investigation to determine whether RNFL thickness is associated with brain structure volumes in nondemented older adults.

METHODS

We measured RNFL thickness by optical coherence tomography and brain structure volumes by 3 T magnetic resonance imaging. Cognitive function was assessed using the Chinese version of Repeatable Battery for the Assessment of Neurological Status. Pearson correlation was initially employed to screen for the potential associations among RNFL thickness, brain structure volumes and cognitive function. And then, multivariable linear regression models were conducted to further examine such associations adjusting for possible confounding factors, including age, sex, years of education and the estimated total intracranial volume (eTIV).

RESULTS

113 participants (≥ 65 years old) were screened and 80 of them (mean age: 68 ± 5.3 years; 48% male) were included in the final analysis. RNFL thickness in temporal quadrant was associated with medial temporal lobes volumes [unadjusted: r = 0.155, P = 0.175; adjusted: β = 0.205 (0.014, 0.383), P = 0.035], and especially associated with the hippocampus volume [unadjusted: r = 0.213, P = 0.062; adjusted: β = 0.251 (0.060, 0.435), P = 0.011] after adjusted for age, sex, years of education and eTIV. Moreover, it showed that RNFL thickness in inferior quadrant [unadjusted: r = 0.221, P = 0.052; adjusted: β = 0.226 (0.010. 0.446), P = 0.041] was significantly associated with occipital lobes volumes after the adjustment of age, sex, years of education and eTIV, and selectively associated with the substructure of lingual gyrus volume [unadjusted: r = 0.223, P = 0.050; adjusted: β = 0.278 (0.058, 0.487), P = 0.014]. In addition, average RNFL thickness was associated with the cognitive domain of visuospatial/constructional [unadjusted: r = 0.114, P = 0.322; adjusted: β = 0.216 (0.006, 0.426), P = 0.044] after the adjustment in these nondemented older adults.

CONCLUSIONS

Quadrant-specific associations exist between RNFL thickness and brain regions vulnerable to aging or neurodegeneration in older adults with normal cognition. These findings would promote further investigations into using RNFL as a noninvasive and less expensive biomarker of neurocognitive aging and AD-related neurodegeneration.

Retinal Nerve Fiber Layer Thinning Is Associated With Brain Atrophy: A Longitudinal Study in Nondemented Older Adults

Backgrounds: Abnormal retinal nerve fiber layer (RNFL) thickness has been observed in patients with Alzheimer’s disease (AD) and therefore suggested to be a potential biomarker of AD. However, whether the changes in RNFL thickness are associated with the atrophy of brain structure volumes remains unknown. We, therefore, set out a prospective investigation to determine the association between longitudinal changes of RNFL thickness and brain atrophy in nondemented older participants over a period of 12 months.

Materials and Methods: We measured the RNFL thickness using optical coherence tomography (OCT) and brain structure volumes by 3T magnetic resonance imaging (MRI) before and after 12 months. Cognitive function was assessed using the Chinese version of Mini-Mental State Examination (CMMSE) and Repeatable Battery for the Assessment of Neurological Status. Associations among the changes of RNFL, brain structures and cognitive function were analyzed with Spearman correlation and multiple linear regression models adjusting for the confounding factors.

Results: Fifty old participants were screened and 40 participants (mean age 71.8 ± 3.9 years, 60% were male) were enrolled at baseline. Among them, 28 participants completed the follow-up assessments. The average reduction of RNFL thickness was inversely associated with the decrease of central cingulate cortex volume after the adjustment of age and total intracranial volume (β = −0.41, P = 0.039). Specifically, the reduction of RNFL thickness in the inferior, not other quadrants, was independently associated with the decline of central cingulate cortex volume after the adjustment (β = −0.52, P = 0.006). Moreover, RNFL thinning, central cingulate cortex atrophy and the aggregation of white matter hyperintensities (WMH) were found associated with episodic memory in these older adults with normal cognition.

Conclusions: RNFL thinning was associated with cingulate cortex atrophy and episodic memory decline in old participants. The longitudinal changes of RNFL thickness are suggested to be a useful complementary index of neurocognitive aging or neurodegeneration.

Perimenopause as a neurological transition state

Perimenopause is a midlife transition state experienced by women that occurs in the context of a fully functioning neurological system and results in reproductive senescence. Although primarily viewed as a reproductive transition, the symptoms of perimenopause are largely neurological in nature. Neurological symptoms that emerge during perimenopause are indicative of disruption in multiple estrogen-regulated systems (including thermoregulation, sleep, circadian rhythms and sensory processing) and affect multiple domains of cognitive function. Estrogen is a master regulator that functions through a network of estrogen receptors to ensure that the brain effectively responds at rapid, intermediate and long timescales to regulate energy metabolism in the brain via coordinated signalling and transcriptional pathways. The estrogen receptor network becomes uncoupled from the bioenergetic system during the perimenopausal transition and, as a corollary, a hypometabolic state associated with neurological dysfunction can develop. For some women, this hypometabolic state might increase the risk of developing neurodegenerative diseases later in life. The perimenopausal transition might also represent a window of opportunity to prevent age-related neurological diseases. This Review considers the importance of neurological symptoms in perimenopause in the context of their relationship to the network of estrogen receptors that control metabolism in the brain.

Fracture as an independent risk factor of dementia: a nationwide population-based cohort study

Dementia is among various diseases affecting the elderly, who is also at a high risk for fractures. This study aimed to evaluate the association between fracture history and sequential risk of dementia in Taiwan.A retrospective cohort study was designed using the claims data of the entire insured residents covered by Taiwan's universal health insurance from 1998 to 2010. A total of 66,797 patients with fractures and 133,594 control subjects without fractures were matched in terms of age (±5 years), sex, and index year and then recruited. Fractures and dementia were defined in accordance with the International Classification of Diseases, 9th Revision, Clinical Modification. The influence of fractures on the risk of dementia was analyzed using a Cox proportional hazards model.After a 12-year follow-up period, 2775 and 3991 incident cases of dementia were reported in exposed and unexposed cohorts, respectively. The overall incidence rate of dementia in individuals with fractures was 41% higher than that in individuals without fractures (6.05 vs 4.30 per 1000 person-years) at an adjusted hazard ratio of 1.38 (95% confidence interval 1.32-1.45) after age, sex, urbanization, and individual disorders or comorbidities were adjusted. Considering fracture location, we found that patients with hip fractures were at a slightly high risk for dementia. The occurrence of multiple fractures at a single visit was also significantly associated with an increased risk of dementia.Fracture history is regarded as an independent risk factor of dementia in individuals aged ≥65 years, particularly those who suffered from multiple fractures and/or fractures located in the hip. Further studies are needed to support an independent role of fracture in dementia considering the clinical information and other comorbidities.

Latest Study on the Relationship between Pathological Process of Inflammatory Injury and the Syndrome of Spleen Deficiency and Fluid Retention in Alzheimer's Disease

Inflammation exists throughout the incidence and progression of Alzheimer's disease (AD). Traditional Chinese medicine (TCM) differentiates the pathogenesis of AD as kidney essence deficiency and qi and blood deficiency as well as blood stasis in syndromes, whose action mechanisms are all associated with the intervention in its inflammatory process. Our preliminary studies both in clinic and in vitro have demonstrated that the syndrome of spleen deficiency and fluid retention has also been an important pathogenesis for the incidence and development of AD. Hence, the paper aims to further illustrate the correlation between inflammatory process in AD and the syndrome of spleen deficiency and fluid retention, laying solid foundation for the application of invigorating the spleen and eliminating the dampness in clinic, and enriching the theoretical connotation for AD prevention and treatment in TCM.

Increased risk of dementia in patients with osteoporosis: a population-based retrospective cohort analysis

Osteoporosis is a common systemic skeletal disease that predominantly affects people older than 50 years and often co-occurs with dementia. The purpose of this study was to evaluate the risk of dementia in osteoporosis patients in Taiwan. Using data from Taiwan's National Health Insurance Research Database (NHIRD), we identified 23,941 patients with osteoporosis from 2000 to 2010 and 47,579 nonosteoporosis control patients, frequency-matched for age, sex, and index year, excluding patients with dementia at the baseline. We conducted univariate and multiple Cox proportional-hazards regression analyses to calculate the hazard ratios (HRs) and 95 % confidence intervals (CIs) of the association between osteoporosis and risk of dementia. After adjustment for potential risk factors, the osteoporosis patients exhibited 1.46-fold and 1.39-fold higher risk of dementia (95 % CI = 1.37-1.56) and Alzheimer's disease (95 % CI = 0.95-2.02), respectively, compared with the matched nonosteoporosis patients. We observed increased risk of dementia in both men and women with osteoporosis. The osteoporosis patients receiving bisphosphonate treatment or estrogen supplementation were associated with significantly lower risk of dementia compared with the osteoporosis patients who did not receive any treatment. Overall, our results suggest higher risks of dementia in osteoporosis patients than in nonosteoporosis patients. Osteoporosis could thus be considered an early risk factor for dementia. Future large-scale double-blind randomized clinical trials are required to clarify the role of medication in osteoporosis-related dementia.

Healthy aging diets other than the Mediterranean: a focus on the Okinawan diet

The traditional diet in Okinawa is anchored by root vegetables (principally sweet potatoes), green and yellow vegetables, soybean-based foods, and medicinal plants. Marine foods, lean meats, fruit, medicinal garnishes and spices, tea, alcohol are also moderately consumed. Many characteristics of the traditional Okinawan diet are shared with other healthy dietary patterns, including the traditional Mediterranean diet, DASH diet, and Portfolio diet. All these dietary patterns are associated with reduced risk for cardiovascular disease, among other age-associated diseases. Overall, the important shared features of these healthy dietary patterns include: high intake of unrefined carbohydrates, moderate protein intake with emphasis on vegetables/legumes, fish, and lean meats as sources, and a healthy fat profile (higher in mono/polyunsaturated fats, lower in saturated fat; rich in omega-3). The healthy fat intake is likely one mechanism for reducing inflammation, optimizing cholesterol, and other risk factors. Additionally, the lower caloric density of plant-rich diets results in lower caloric intake with concomitant high intake of phytonutrients and antioxidants. Other shared features include low glycemic load, less inflammation and oxidative stress, and potential modulation of aging-related biological pathways. This may reduce risk for chronic age-associated diseases and promote healthy aging and longevity.

Value-based assessment of pharmacodiagnostic testing from early stage development to real-world use

Disease etiology may be regarded as a consequence of both genotypic and biochemical phenomena, which impact individual patients in different ways. Disease prognosis, beneficial treatment response, and susceptibility to adverse drug effects are often intimately tied to individual biology. Clinical and genetic biomarkers applied individually or in concert are increasingly used to stratify patient populations in terms of prognosis, therapeutic benefit, or safety. As a result, clinical trialists are challenged to design studies that reflect these determinants of outcome, to optimize the patient's eventual clinical course both in the trial and in actual practice. These designs are informed both by preclinical studies and by real-world research that can establish proof of concept for a novel biomarker and provide a basic understanding of the relationship between biomarker and clinical outcome. As clinical and real-world studies unfold, a deeper understanding of the nature of the biomarker and its potential uses in drug development is gained. Specifically, one can eventually define the biomarker as prognostic (i.e., predicts disease progression), predictive (predicts treatment response or adverse outcome(s)), or exhibiting both prognostic and predictive properties. One must further validate the performance of these emerging biomarkers, again in both the trial and real-world environments. The eventual adoption of the biomarker as a useful pharmacodiagnostic test is premised upon this early translational research. In this article, the development and validation of predictive and prognostic biomarkers is discussed by using selected examples that highlight factors contributing to the valuation of biomarkers and their application to personalized medicine in the real world.

Increased risk of dementia in people with previous exposure to general anesthesia: a nationwide population-based case-control study

BACKGROUND

Dementia, which leads to disability, is one of the important diseases occurring among older populations. However, the exact mechanism of the disease remains unknown. The potential risk factor of general anesthesia (GA) in the development of dementia is a controversial topic. Therefore, this study aimed to evaluate the association between previous exposure to different GA types and the incidence of dementia.

METHODS

Using the claims data of 1 million insured residents covered by Taiwan's universal health insurance from 2005 to 2009, 5345 newly diagnosed dementia patients older than 50 years were eligible for the study group. The control group, which consisted of 21,380 individuals without dementia, was matched for age, gender, and index date. GA was categorized into three subtypes: endotracheal tube intubation general anesthesia (ETGA), intravenous injection general anesthesia (IVGA) or intramuscular injection general anesthesia (IMGA), and heavy sedation. The multiple logistic regression model was used for analyses.

RESULTS

Individuals exposed to surgery under ETGA (odds ratio [OR], 1.34; 95% confidence interval [CI], 1.25-1.44) and those exposed to surgery under IVGA or IMGA (OR, 1.28; 95% CI, 1.14-1.43) were at significantly higher risk of dementia in a dose-response relationship (P < .0001), whereas surgery under heavy sedation was not associated with increased risk of dementia (OR, 1.04; 95% CI, 0.68-1.59). The dementia risk for subjects with diabetes mellitus who received surgery under ETGA (OR, 1.59; 95% CI, 1.42-1.78), hypertension (OR, 1.98; 95% CI, 1.78-2.21), atherosclerosis (OR, 1.35; 95% CI, 1.22-1.50), or after having experienced a stroke (OR, 3.52; 95% CI, 3.13-3.97), but no interaction was found between surgery under ETGA and depression for the risk of dementia.

CONCLUSIONS

A history of previous exposure to surgery under GA might be associated with an increased risk of dementia, particularly in subjects who have undergone repeated exposure to GA. In addition, subjects who had received surgery under ETGA with comorbidities such as stroke, hypertension, diabetes mellitus, and atherosclerosis could have a potential relationship with dementia risk.

Where, when, and in what form does sporadic Alzheimer's disease begin?

PURPOSE OF REVIEW

Intraneuronal lesions consisting of abnormal tau protein are seen to develop from the beginning until the end-phase of the pathological process underlying Alzheimer's disease. This review highlights the earliest phase of this process.

RECENT FINDINGS

Development of abnormal tau frequently begins during childhood or puberty in nuclei of the lower brainstem sending diffuse projections to the cerebral cortex. Nonfibrillar abnormal tau material first occurs in the proximal axon of projection neurons in the locus coeruleus. Subsequently, a similar material (pretangle material) fills the somatodendritic compartment. In contrast with the pretangle material in cell bodies and dendrites, the nonfibrillar material in the axon normally does not convert into stable fibrillary inclusions.

SUMMARY

Projection neurons (not only those of the locus coeruleus) are sturdy and can survive for a lifetime despite the existence of Alzheimer-related abnormal tau. Currently, little understood mechanisms most probably exist that enable neurons to fulfill their general functions even when severe tau pathology is present. The proclivity of predisposed neuronal types to develop abnormal tau may be intrinsic to the human brain. However, the tempo of disease progression reveals considerable individual differences, thereby offering opportunities to study conditions that may modify disease progression.

Risk factors for mild cognitive impairment among Mexican Americans

BACKGROUND

Although a great deal of literature has focused on risk factors for mild cognitive impairment (MCI), little published work examines risk for MCI among Mexican Americans.

METHODS

Data from 1628 participants (non-Hispanic n = 1002; Mexican American n = 626) were analyzed from two ongoing studies of cognitive aging and Alzheimer's disease, Project FRONTIER (Facing Rural Obstacles to health Now Through Intervention, Education & Research) and TARCC (Texas Alzheimer's Research & Care Consortium).

RESULTS

When looking at the full cohorts (non-Hispanic and Mexican American), age, education, Apolipoprotein E (APOE) ε4 status and gender were consistently related to MCI diagnosis across the two cohorts. However, when split by ethnicity, advancing age was the only significant risk factor for MCI among Mexican Americans across both cohorts.

CONCLUSIONS

The current data suggest that many of the previously established risk factors for MCI among non-Hispanic cohorts may not be predictive of MCI among Mexican Americans and point to the need for additional work aimed at understanding factors related to cognitive aging among this underserved segment of the population.

Prevention strategies for Alzheimer's disease

Symptomatic treatment during the dementia stage of Alzheimer's disease(AD) cannot delay or halt the progression of this disease. Therefore, prevention in the preclinical stage is likely the most effective way to decrease the incidence of this age-associated neurodegenerative condition, and its associated burden for individuals and society. Age, gender, family history, ApoE4, systolic blood pressure, body mass index, total cholesterol level and physical activity are all used as component of dementia risk score. There have been numerous challenges in conducting primary prevention trials in AD. Enrichment strategies for prevention studies include studying those subjects with more risk factors for AD, such as older age, those with a positive family history of late onset AD, and those who are ApoE4 positive. Each of these strategies is designed to increase the probability of developing AD thereby decreasing the sample size or the duration of follow up. Another strategy would be to target directly the pathophysiology of AD in its preclinical stages and use the biomarkers in prevention trial as surrogate markers. This will be done first in carriers of dominantly inherited early onset AD. As this research takes place networks of memory clinics must prepare to transfer new knowledge to persons interested in a preventive approach to AD.