- Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the leading cause of dementia worldwide, primarily affecting older adults. It gradually impairs memory, thinking, language, and the ability to carry out daily tasks. The condition advances over years, beginning with mild forgetfulness and progressing to severe cognitive and functional decline. AD has a profound impact not only on the affected individual but also on caregivers and health care systems globally.
- At the microscopic level, Alzheimer’s disease is characterized by the accumulation of two abnormal protein structures in the brain: amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs).
- Amyloid-beta plaques are sticky clumps that form outside neurons, disrupting cell communication and triggering inflammatory responses.
- Neurofibrillary tangles, composed of hyperphosphorylated tau protein, develop inside neurons and interfere with nutrient and signal transport.
- Together, these pathologies lead to synaptic dysfunction, widespread neuronal death, and brain atrophy, especially in areas crucial for memory and learning like the hippocampus and cortex.
- The disease typically progresses through several stages. In the preclinical stage, pathological changes may occur years before symptoms appear. This is followed by mild cognitive impairment (MCI), during which individuals experience noticeable memory lapses that do not yet significantly disrupt daily life. As the disease advances to Alzheimer’s dementia, cognitive decline becomes more pronounced and affects reasoning, judgment, language, and the ability to live independently. Behavioral and psychological symptoms such as depression, anxiety, and agitation often emerge in later stages.
- Several factors increase the risk of developing Alzheimer’s disease. Age is the most significant risk factor, with incidence rising sharply after the age of 65. Genetics also play a role; the presence of the APOE ε4 allele is a strong risk factor for late-onset AD, while rare mutations in the APP, PSEN1, and PSEN2 genes cause early-onset familial forms of the disease. Additionally, modifiable lifestyle factors—such as cardiovascular health, education, physical activity, and diet—have been shown to influence the risk of developing AD, highlighting opportunities for prevention.
- Diagnosis of Alzheimer’s disease is based on clinical evaluation, cognitive testing, neuroimaging, and biomarker analysis. Tools like the Mini-Mental State Examination (MMSE) or Montreal Cognitive Assessment (MoCA) help assess cognitive function. MRI scans may reveal brain atrophy, while PET imaging can detect amyloid or tau deposits. Cerebrospinal fluid (CSF) analysis often shows decreased levels of Aβ42 and elevated levels of total tau and phosphorylated tau. Blood-based biomarkers are also emerging as accessible diagnostic tools.
- Although there is currently no cure for Alzheimer’s disease, several treatments aim to relieve symptoms and slow progression. Cholinesterase inhibitors such as donepezil and rivastigmine improve communication between neurons by increasing acetylcholine levels. Memantine, an NMDA receptor antagonist, helps regulate glutamate activity and protect against excitotoxicity. More recently, monoclonal antibodies targeting amyloid-beta, such as aducanumab and lecanemab, have been approved, though their clinical benefits remain under debate. In addition to pharmacological treatments, non-drug interventions including cognitive training, physical activity, structured routines, and caregiver support play a crucial role in management.
- Ongoing research in Alzheimer’s disease focuses on earlier diagnosis, disease-modifying therapies, and understanding the underlying biology of neurodegeneration. New areas of interest include the role of neuroinflammation, the gut-brain axis, and lifestyle interventions. Advances in precision medicine and biomarker-guided approaches hold promise for improving outcomes through tailored prevention and treatment strategies. As the global burden of Alzheimer’s disease continues to rise, addressing it remains a top priority in neuroscience and public health.
