OVERVIEW OF ALZHEIMER’S DISEASE

Abstract

Alzheimer's disease is a gradually advancing neurodegenerative disorder that progressively affects cognitive and behavioral functions, including memory, comprehension, language, attention, reasoning, and judgment. It represents the most common form of dementia among individuals aged 65 and older, accounting for at least two-thirds of dementia cases within this age group. Early-onset Alzheimer’s, which occurs before the age of 60, is uncommon, affecting less than 10% of patients with the disease. While there is currently no cure for Alzheimer's, certain treatments are available that can help alleviate some symptoms. Based on the degree of cognitive impairment, Alzheimer's disease can be classified into preclinical (or presymptomatic), mild, and dementia-stage categories, which differ from the DSM-5 classification of Alzheimer's. The initial and most frequently observed symptom is episodic short-term memory loss, while long-term memory tends to remain relatively unaffected. This impairment in short-term memory can often be detected in the majority of patients, even if it is not the primary presenting symptom. As the disease progresses, it leads to difficulties in problem-solving, judgment, executive functioning, motivation, and organization, resulting in challenges with multitasking and abstract thinking. Early stages of the disease may show varied levels of executive dysfunction, from mild to significant. Language issues and visuospatial impairments follow, with later stages leading to challenges in performing learned motor tasks due to dyspraxia, as well as symptoms like olfactory dysfunction, sleep disturbances, and extrapyramidal motor signs (such as dystonia, akathisia, and Parkinsonian symptoms). In advanced stages, primitive reflexes, incontinence, and complete dependence on caregivers typically emerge.

This article discusses the broader health impact of Alzheimer's disease, including aspects such as the prevalence, mortality rates, healthcare costs, and the effects on caregivers and society (Joshua D. Niznik, Jennifer L. Lund, Laura C. Hanson, Cathleen Colón-Emeric, Casey J. Kelley, Meredith Gilliam, Carolyn 2024). The report also highlights the challenges in addressing the care requirements of an increasing population of individuals with Alzheimer’s dementia in the United States, particularly in terms of caregiving demands (García-Batalloso, Isabel Cabrera, Andrés Losada-Baltar, Laura Mérida-Herrera, Javier Olazarán, María Márquez-González, Network Analysis of Comorbid Depressive and Anxious Symptoms in Family Caregivers of People with Dementia 2023). By 2050, projections indicate there may be around 13.8 million Americans aged 65 and older living with Alzheimer’s dementia, a rise from an estimated 5.8 million today. In 2018, Alzheimer's disease accounted for 122,019 deaths in the U.S., making it the sixth leading cause of death overall and the fifth among those aged 65 and above. Between 2000 and 2018, deaths due to Alzheimer’s disease rose by 146.2%, contrasting with declines in mortality rates for stroke, HIV, and heart disease.

Moreover, in 2019, over 16 million family members and unpaid caregivers contributed 18.6 billion hours to caring for individuals with Alzheimer’s or other dementias. The estimated value of this care amounts to approximately $244 billion, yet it also brings significant costs, such as increased emotional strain and negative impacts on the mental and physical health of caregivers. For those aged 65 and older with Alzheimer’s or other dementias, Medicare payments per person are over three times higher than for individuals without these conditions, while Medicaid payments are more than 23 times greater. In 2020, total expenses on healthcare, long-term care, and hospice services for seniors aged 65 and above with dementia are projected to reach $305 billion. As the number of Americans affected by Alzheimer’s disease grows, so does the burden on caregivers (2024 Alzheimer's Disease Facts and Figures, Alzheimer’s & Dementia). The shortage of dementia care specialists further exacerbates these challenges, placing additional pressure on primary care physicians who may lack adequate training for managing dementia care. The report provides recommendations on how to maintain quality care in primary care settings, despite the shortage of specialists and training limitations (Hebert LE, Beckett LA, Scherr PA, Evans DA. Annual incidence of Alzheimer’s disease in the United States projected to the years 2000 through 2050).

Globally, an estimated 47 million people are currently living with Alzheimer’s disease, and this number is expected to rise to 131 million by 2050. Alzheimer’s remains the most prevalent form of dementia, and the worldwide cost associated with dementia was reported to be $818 billion. Although there is no cure or substantial treatment to slow the disease’s progression, early detection can be crucial. Early diagnosis aids individuals with dementia and their families in preparing for the progression of the disease, increases understanding of the disease’s course, and can potentially accelerate the development of treatments (Hebert LE, Bienias JL, Aggarwal NT, Wilson RS, Bennett DA, Shah RC, et al. Change in risk of Alzheimer’s disease over time 2020). A novelty detection-based approach has been explored for diagnosing Alzheimer's disease and mild cognitive impairment using EEG data. Researchers are investigating a range of biomarkers to enable timely diagnosis, with promising results emerging from combining brain Magnetic Resonance Imaging (MRI) and machine learning to differentiate between various dementia types and normal controls. This study examined whether MRI scans, paired with either three texture features and random forest analysis or three-dimensional convolutional neural networks, could facilitate the early detection of Alzheimer's disease. Data for this study included 2,688 MRI scans from 811 participants provided by the Alzheimer’s Disease Neuroimaging Initiative. In terms of diagnostic stages, the highest accuracy achieved in distinguishing among four different classes was 41.1%. For categorizing impaired individuals based on whether they would progress to Alzheimer's or remain stable, the accuracy reached 60.3% (Xiaojun Xu, Weiwei Ruan, Fang Liu, Qingyao Liu, Yongkang Gai, Ying Su, Zhihou Liang, Xun Sun, Xiaoli Lan, Characterizing Early-Onset Alzheimer Disease Using Multiprobe PET/MRI, Clinical Nuclear Medicine, 2023). Additionally, U.S. mortality data for 2018 highlights Alzheimer's disease as a significant cause of death, emphasizing the need for improved diagnostic methods and early intervention (Xu JQ, Murphy SL, Kochanek KD, Arias E. Mortality in the United States, 2018. NCHS Data Brief; No. 355. Hyattsville, MD: National Center for Health Statistics. 2020).