What is Alzheimer’s disease?

Alzheimer’s disease¹, also referred to simply as Alzheimer’s, is a progressive disease that affects memory and causes a decline in other cognitive abilities.

Alzheimer’s² is irreversible. As it is progressive, the disease gets worse as time goes on, slowly destroying memory and processing skills. Over time³, basic skills, such as the ability to carry a conversation and respond to one's environment as normal, start to decline. Even the simplest or most familiar activities can become incredibly challenging.

Alzheimer’s disease itself is named after Dr. Alois Alzheimer. Dr. Alzheimer discovered this disease after noticing changes in the brain tissue of a woman who had died of an unusual mental illness. Her brain contained abnormal clumps called amyloid plaques and tangled bundles of fibers known as neurofibrillary.

These plaques and tangles are still thought of as one of the main physical features of the disease. When they form, the connections between the neurons in the brain lessen, lessening their ability to transmit signals to the muscles and organs over time.

Currently, there is no cure for Alzheimer’s. This is one of the most difficult parts about living with the disease, whether you or a loved one is affected. Currently, Alzheimer’s is ranked as the sixth leading cause of death⁴ in the United States. However, for those aged 65 and older, it ranks third (behind only heart disease and cancer).

Alzheimer’s gum disease

A recent study⁵ from Science Advances shows a link between Porphyromonas gingivalis, the bacteria associated with periodontal disease (gum disease), and Alzheimer’s. After analyzing the brain tissue, spinal fluid, and saliva of patients with Alzheimer’s, researchers found that 96% of the 53 brain tissue samples contained gingipains, the toxic enzyme secreted by P. gingivalis.

Further testing confirmed that P. gingivalis can travel from the mouth to the brain. This bacteria can then begin to destroy the neurons in the brain over time. This explains the biological mechanism by which gum disease bacteria can play a role in the development of Alzheimer’s disease.

As a result, it is encouraged that older adults and people who are at risk for Alzheimer’s maintain diligent oral hygiene. Over 50% of people 30 and over have some kind of gum disease—this rate jumps to 68% in those 65 and older.

How common is Alzheimer’s?

Alzheimer’s is a growing epidemic and is becoming more common⁶ as time goes on. More than 5.8 million Americans have Alzheimer’s disease. By 2050, it is projected that 14 million Americans aged 65 and older could be living with Alzheimer’s.

It is estimated that 500,000 new cases of Alzheimer’s will be diagnosed this year alone. At least 50 million people are believed to be living with Alzheimer’s worldwide, and if a cure is not found, these rates are projected to reach 150 million by the year 2050.

As a result, Alzheimer’s is the only leading cause of death in America that continues to be on the rise, rather than declining. The number of deaths associated with Alzheimer’s disease increased by 139% from 2000–2016 (while heart disease-related deaths, for example, decreased by 6%).

Alzheimer’s disease is also the leading cause of dementia, a group of symptoms characterized by cognitive decline. Alzheimer’s disease accounts for 60–80% percent of dementia cases overall.

What causes Alzheimer’s disease?

Researchers have not identified one single definitive cause⁷ of Alzheimer’s. There are multiple factors that may play a role in the development of the disease, such as genetics, lifestyle, and environment. Whether an individual will develop Alzheimer’s is less dependent on one key trait or factor and more so on the presence of a combination of risk factors.

Biologically, Alzheimer’s disease is caused by the progression of neurodegenerative brain cell death. In people with Alzheimer’s, the connections between the cells in the brain’s nerves become fewer and fewer. This is due to the formation of plaques and tangles⁸ in the brain.

These plaques are made up of Beta-amyloid, a leftover protein. When Beta-amyloid fragments cluster together, they form amyloid plaques. These plaques have a toxic effect on the brain’s nerve cells (called neurons).

The “tangles” are made up of tau proteins, which affect nutrients and the essential functions of the brain. In people with Alzheimer’s, these proteins change shape, organizing themselves into structures called neurofibrillary tangles. These tangles disrupt the proper transport of facilities in the brain, causing neurons to degenerate.

Risk factors for Alzheimer’s disease

Researchers do not understand what exactly causes neurons to degenerate at such a high rate in people with Alzheimer’s. However, some risk factors⁹ are believed to contribute to the development of the disease, including:

• Age: Aging is the greatest known risk factor for Alzheimers. It is not a direct cause in any way, but it does increase risk. After the age of 65, the risk of Alzheimer’s doubles every single year.
• Family history: Those with a first-degree relative (such as a parent or sibling) with Alzheimer’s disease are more likely to develop it themselves.
• Genetics: Carrying certain genes can play a role in the likelihood of developing Alzheimer’s. While many people with these genes may go on to develop Alzheimer’s, the presence of these genes is not a guarantee that you will have the disease.
• Traumatic brain injury: Having a serious head injury can increase your risk for Alzheimer’s, as there has been a link found between cognitive decline and injuries to the brain.
• Heart and brain health: Both heart health¹⁰ and brain health have been shown to have a direct correlation with Alzheimer’s. As the brain is provided with oxygen and nutrients by the heart, heart-related conditions, such as high blood pressure, high cholesterol, and diabetes, can put you at risk.

• Race/ethnicity¹¹: Hispanic Americans are about 1.5 times more likely and African-Americans about 2 times more likely to develop Alzheimer’s disease than white Americans.

Alzheimer’s disease symptoms

Alzheimer’s disease causes progressive cognitive decline. This can lead to a number of signs and symptoms¹², including:

• Memory loss: This is one of the key symptoms of Alzheimer’s. This can manifest itself in many ways. A person with Alzheimer’s may repeat statements over and over or forget conversations and events. They may also misplace possessions or put them in illogical locations, forget the names of people and objects, or have trouble finding the right words to express themselves.
• Decline in reasoning and thinking skills: This can appear as difficulty concentrating and thinking, especially about abstract things like numbers.
• Poor judgment: This can manifest itself by saying something in a social setting that is not appropriate, or wearing clothing that is not fit for the weather outside.
• Difficulty performing basic tasks: Even the smallest things become hard for someone with Alzheimer’s. It can eventually degrade to forgetting to take baths, and not being able to get dressed.
• Changes in personality and behavior: This can show itself in the form of depression, apathy, social withdrawal, and severe mood swings.

Complications from Alzheimer’s disease

Unfortunately, because Alzheimer’s is a progressive disease, it worsens over time, often leading to health complications and difficulties with day-to-day life. Some common complications associated with Alzheimer’s include:

• Restlessness and agitation¹³: People with Alzheimer’s commonly feel anxiety or frustration over not being able to perform tasks or use skills (such as speech) like they used to. The feeling of agitation about lessening functions can linger for quite a bit after the onset of the disease.

• Incontinence:Problems with going to the bathroom: As Alzheimer's disease progresses gets worse, the function of going to the bathroom can become more difficult gets harder to perform. This can lead to Incontinence (unintentional elimination) that can occur, so it is important to look out for an Alzheimer’s patient in this regard.
• Depression¹⁴ can also occur as a result of all of the added stresses experienced by people with Alzheimer’s.

• Infection¹⁵: People with Alzheimer’s often don’t notice infections in their early stages. Infections may also develop as a result of declined hygiene and the loss of bodily functions. Respiratory problems, such as pulmonary aspiration and pneumonia, are common, as well.

• Malnutrition is also common, as people with Alzheimer’s may forget to eat or drink. They may also have difficulty chewing or swallowing food or even forget how to eat or drink.

Alzheimer’s disease stages

Because Alzheimer’s is a progressive disease, it has been assigned stages¹⁶ that delineate its progression according to severity. Knowing the specific stages a patient’s Alzheimer’s has progressed to can help healthcare providers and loved ones make decisions on the best care and treatment.

Alzheimer’s disease is broken up into the following stages:

• Preclinical stage: This stage occurs years before the signs and symptoms of Alzheimer’s may become apparent and can last for years. During this time, it is important to get CT scans and check-ups in order to detect the early signs of Alzheimer’s in the brain.
• Mild/early stage: During this stage, the symptoms of Alzheimer’s are mild. Patients may experience occasional forgetfulness, such as difficulty remembering a name or forgetting where an object was placed.
• Moderate/middle stage: This is the longest-lasting of all the stages associated with Alzheimer’s. Symptoms during this stage include problems learning new things, trouble remembering key information (such as one’s address and phone number), and problems reading and writing. Patients may require extra care and attention, with some needing more consistent supervision.
• Severe/late stage: This is the last stage of the disease, at which point the symptoms of Alzheimer’s have become the most severe. During this time, patients may experience the loss of physical abilities or motor skills, such as sitting, eating, and walking. They may also forget words and phrases entirely or be unaware of their surroundings. At this stage, patients require constant care and supervision.