Effect of Alzheimer’s on the Brain
Alzheimer’s disease is present years before symptoms of memory loss and other cognitive deficits appear. This is referred to as the preclinical stage of Alzheimer’s disease, in which people appear to function normally but a number of toxic changes within the brain are progressing. Among the abnormal changes, two primary features have been identified (38):
- Amyloid plaques—These consist of insoluble deposits of beta-amyloid, a toxic protein fragment. Generally found in the spaces between the brain’s nerve cells, they are more abundant in people with Alzheimer’s disease.
- Neurofibrillary or tau tangles —Found inside the nerve cell, these consist of abnormally shaped or twisted protein collections that stick together and build up, eventually disrupting cell communication and even causing cell death.
These toxic changes can cause healthy neurons to shrink, lose connections with other brain cells, stop functioning, and even die. As more and more neurons are affected, the given brain areas lose volume and shrink (see figure Normal vs Alzheimer Brain).This appears to initially occur in the hippocampus (a critical area for learning, short-term memory, and conversion of short-term memories to long-term storage in other areas of the brain) but then spreads to other areas of the brain, eventually affecting one’s cognitive abilities. By the final stage of Alzheimer’s, the damage is pervasive and brain volume significantly declines.
While Alzheimer’s can occur early in life, 95 percent of the cases are late onset and occur after the age of 60 years. Early-onset Alzheimer’s is thought to be caused by gene changes inherited from a parent, but a small number of cases currently have no specifically identified cause. The more prevalent late-onset form results from a variety of factors that occur and progress over decades. These include possible genetic mutations (such as the apolipoprotein E gene, or APOE), environmental and social factors, and poor lifestyle choices.
Since Alzheimer’s disease develops over a period of many years, the condition can go unrecognized until outward symptoms are displayed. Early in the Alzheimer’s disease process, symptomatic changes are very subtle. You or your loved one may experience memory problems that are fairly mild but slightly greater than expected based on age, but they generally do not interfere with everyday activities. As Alzheimer’s progress, memory challenges increase and other cognitive difficulties are manifested, such as personality and behavior changes, difficulty handling money and paying bills, challenges with multistep tasks such as dressing and cooking, and wandering. At the severe stage of Alzheimer’s, people lose their ability to communicate, often becoming completely dependent on others for their daily care and perhaps requiring admittance to a care facility.
Having a family member diagnosed with Alzheimer’s disease is a daunting experience as you face the reality that you or your loved one has a serious, progressive, and ultimately fatal neurodegenerative condition. As the cognitive and physical abilities of people with Alzheimer’s progressively decline, family members face challenging emotional and financial decisions regarding long-term care. Thus early diagnosis, support group participation, appropriate nutrition, and regular physical activity are important for both the person with Alzheimer’s and the health of those providing care.
Once considered a relatively rare disorder, Alzheimer’s disease is listed as the sixth leading cause of death in the United States and considered a major public health challenge affecting more than 5 million Americans, the majority of whom are over the age of 65 years. The prevalence of dementia, with Alzheimer’s disease accounting for two-thirds of the cases, increases with age, affecting nearly 14 percent of the population over the age of 70 years. This creates a challenging public health issue, as the prevalence of neurodegenerative conditions like Alzheimer’s doubles every five years beyond age 65 (38). At the dawn of the 21st century, approximately 35 million Americans (12.4 percent of the total population) were 65 years or older. By 2015, nearly 46 million Americans (15 percent) had reached the age of 65; and by 2030, when the last of the baby boom generation hits this milestone, one in five Americans will be over age 65 (14).
Alzheimer’s disease is named after Dr. Alois Alzheimer, the German neurologist, and psychiatrist who first described the condition, in 1906, when he reported on changes in the brain tissue in a woman who had died of an unusual mental illness. Her cluster of symptoms included memory loss, language challenges, disorientation, behavioral problems, and hallucinations. Following her death, Dr. Alzheimer studied her brain tissue and described two of the primary hallmarks of Alzheimer’s disease—numerous abnormal clumps or globs of sticky proteins (now referred to as amyloid plaques) and tangled bundles of fibers within the neurons (now called neurofibrillary or tau tangles) (38).
Despite intensive and ongoing research efforts, currently, there is no medication or other medical intervention that can “cure” Alzheimer’s. Thus medical treatment focuses on managing symptoms and prolonging, for as long as possible, the person’s ability to carry out activities of daily living.
How does the brain work to regulate daily activities?
The brain is a phenomenal organ that allows each person to carry out every aspect of daily living, from internal body functions such as breathing and digestion to conscious functions such as speaking, moving, and making decisions. The brain is made up of more than 100 billion nerve cells or neurons and is served by over 400 billion tiny blood vessels called capillaries. The vast majority of the brain consists of the left and right cerebral hemispheres, which are connected by a large bundle of nerve fibers. Each of these cerebral hemispheres has an outer layer (cerebral cortex) where the brain regulates cognitive functions such as learning, remembering, and decision making; controlling voluntary movements, and processing sensory information.