Alzheimer’s Disease: Why Don’t We Have A Cure For It?
If scientists can develop effective new vaccines for COVID-19, a previously unknown virus that began spreading around the world only four years ago, why is there still no cure for Alzheimer’s disease, a devastating disease that was first described over 100 years ago?
Donald Weaver, a practicing medicinal chemist and clinical neurologist who treats Alzheimer’s disease patients, raised this thought-provoking question in an article for The Conversation. Unfortunately, Weaver does not have an answer to give his patients and their families.
“I share in the frustration, indeed anger, of people and families when I tell them that I have no cure to offer,” Weaver, the director, and a senior scientist at the Krembil Research Institute, University Health Network, University of Toronto, wrote. “Although it was first officially described 115 years ago, and of course, existed long before that, we still do not have a cure for this devastating disease. Why?”
More than 55 million people worldwide are living with Alzheimer’s disease and other dementias, and 10 million new cases are reported every year, according to the World Health Organization. The Alzheimer’s Association reports an estimated 6.7 million adults age 65 and older in the United States are living with Alzheimer’s, the most common type of dementia. Alzheimer’s disease accounts for 60-80 percent of dementia cases, according to the association.
Alzheimer’s is a progressive disease that eventually disrupts a person’s daily living activities. Since memory loss is one of the most prominent symptoms of Alzheimer’s, many older adults believe they are developing the disease when they forget things. Forgetfulness, however, is a normal part of aging, but Alzheimer’s disease is not.
Besides memory loss, the National Institutes of Health reports that a person with mild Alzheimer’s may experience other symptoms, including:
- Poor judgment leading to bad decisions
- Losing track of dates or knowing their current location
- Taking longer to complete normal daily tasks
- Repeating questions or forgetting recently learned information
- Having trouble handling money and paying bills
- Wandering and getting lost
- Mood and personality changes
- Losing things or misplacing them in odd places
Challenges to Finding a Cure for Alzheimer’s
While there are treatments that temporarily reduce Alzheimer’s symptoms, there is no cure for the disease. The road to finding a successful treatment for Alzheimer’s has been anything but smooth, and Weaver touched on several reasons why:
1. Underfunding of Alzheimer’s Research
Alzheimer’s disease research is severely underfunded, compared to COVID-19, cancer, heart disease, and HIV/AIDS, and this could be due to the mistaken belief that the disease only affects older adults, Weaver said. However, five to 10 percent of people living with Alzheimer’s are under 65 years old, and some are even in their 40s. While people who inherit rare genes can develop Alzheimer’s in their 30s and 40s, the majority of people with Alzheimer’s are 65 and older, according to the Alzheimer’s Association.
2. Conflicting Theories on Alzheimer’s
The human brain is complicated, which is why there are different theories on what causes Alzheimer’s, including:
- The Amyloid-Beta Hypothesis. This leading hypothesis suggests abnormal protein deposits of beta-amyloid plaques and tau tangles clump together in the region of the brain that involves memory and cognition. These deposits eventually kill brain cells, which causes memory loss and a decrease in cognition. Although there is a wealth of research that supports this hypothesis, Weaver noted that multiple drugs that have been developed to block the aggregated beta-amyloid have “dramatically failed.”
- The Neuroinflammation Theory. This theory proposes that chronic inflammation in the brain plays a significant role in the development and progression of Alzheimer’s. The inflammation is caused by an excessive release of microglia, which are immune cells of the central nervous system. This excessive release causes neuroinflammation and damage to neurons. Drugs designed to target this theory are still in the early stages of development.
Other theories include significant dysfunctions of synapses, which are the junctions between brain cells, and the disease of mitochondria, the structures in a cell that generate the energy needed to power cells in the body, including the brain.
Difficulty Developing Effective Drugs
In 2023, the U.S. Food and Drug Administration gave full approval to Leqembi, the first drug shown in clinical studies to slow the progression of Alzheimer’s in people in the early stages of the disease. While clinical trials have shown Leqembi to be effective, the drug does not cure the disease.
It won’t be an easy journey to find a cure for Alzheimer’s disease, and even if these theories result in drug development, Weaver said the medications may fail due to various reasons, including the following:
- 1. Alzheimer’s is a very long, chronic disease that may be present 20 to 30 years before the first symptoms become obvious.
“Giving the drug when a person becomes symptomatic may be too late for it to make any difference,” Weaver wrote. “But we do not have the ability to diagnose it 30 years before the first symptoms, and even if we could, we would need to consider the ethics of giving a potentially toxic drug long-term to someone who may or may not get a disease in three decades.”
- 2. The chronic nature of Alzheimer’s disease requires years of long, expensive clinical trials before knowing whether the drugs will work.
- 3. Alzheimer’s may not simply be one disease but a collection of similar diseases. Weaver pointed out that a 52-year-old patient in the early stages of Alzheimer’s will have a different clinical course from an 82-year-old with late-onset Alzheimer’s, which develops when someone is 65 or older.
Despite the hurdles, there is “a wealth of fascinating and encouraging research is taking place in laboratories around the world,” Weaver wrote.
Over the past century, the science and the pharmaceutical industry have had success against many other diseases from “picking low-hanging fruit,” or things that can be readily done to achieve success.
“Alzheimer’s disease is not a low-hanging fruit, but the apple at the very top of the tree, and scientists are going to have to climb a lot of branches—many of which have never been trodden upon—on the way to a cure,” Weaver wrote. “But we’ll get there.”
Source Links:
https://theconversation.com/why-dont-we-have-a-cure-for-alzheimers-disease-156473
https://www.who.int/news-room/fact-sheets/detail/dementia#:~:text=Currently%20more%20than%2055%20million,nearly%2010%20million%20new%20cases.
https://www.alz.org/alzheimers-dementia/facts-figures#:~:text=in the U.S.-,Prevalence,living with Alzheimer’s in 2023.
https://www.nia.nih.gov/health/alzheimers-symptoms-and-diagnosis/what-are-signs-alzheimers-disease
