What is dementia?
Dementia is not a specific disease. It’s an overall term that describes a wide range of symptoms associated with a decline in memory or other thinking skills severe enough to reduce a person’s ability to perform everyday activities. Alzheimer’s disease accounts for 60 to 80 percent of cases. Vascular dementia, which occurs after a stroke, is the second most common dementia type. But there are many other conditions that can cause symptoms of dementia, including some that are reversible, such as thyroid problems and vitamin deficiencies.
The most common symptoms of dementia are:
- Memory loss
- Difficulty communicating
- Inability to learn new things
- Difficulty with planning and organizing
- Difficulty with coordination and motor functions
- Confusion and disorientation
These symptoms occur because dementia damages brain cells. The damage interferes with the ability of brain cells to communicate with each other. When brain cells cannot communicate normally, thinking, behavior and feelings can be affected.
The brain has 100 billion nerve cells, or neurons, that make up networks. Each network has specialized functions such as thinking, learning, memory and planning. When dementia damages neurons, the networks that control these functions break down.
What causes dementia?
Dementia has many causes. Some, like Alzheimer’s disease, have no known cure. But several other causes of dementia can be treated or reversed if caught early. The most common types of dementia include:
Alzheimer’s disease
This is the most common cause of dementia, accounting for 60 to 80% of cases. It is a progressive brain disease that slowly destroys memory and thinking skills. Eventually, Alzheimer’s disease affects the ability to carry out the simplest tasks. In most people with Alzheimer’s, symptoms first appear after age 60. The risk increases with age. About 5% of people with the disease have early-onset Alzheimer’s, which begins before age 65.
In Alzheimer’s disease, high levels of certain proteins inside and outside brain cells make it hard for brain cells to stay healthy and communicate with each other. The brain region called the hippocampus is the center of learning and memory and is one of the first places to be damaged. As Alzheimer’s spreads through the brain, cells and whole brain regions begin to shrink. By the final stage of Alzheimer’s, damage is widespread, and brain tissue has shrunk significantly.
Scientists still don’t fully understand what causes Alzheimer’s disease. The leading hypothesis is that it is caused by a buildup of two abnormal proteins in the brain:
- Beta-amyloid – beta-amyloid protein pieces collect outside neurons and form sticky plaques.
- Tau – Tau protein pieces build up inside neurons and block the transport of nutrients and other essential molecules.
This damage eventually kills neurons.
There are probably multiple factors that determine why the abnormal proteins accumulate in the first place, including:
- Genetics – Less than 5 percent of Alzheimer’s cases are caused by inherited gene mutations.
- Health conditions – Heart disease, stroke, high blood pressure and diabetes are all risk factors.
- Lifestyle factors – Diets high in saturated fats and simple carbohydrates have been linked to increased risk.
- Traumatic brain injury – Past head trauma may increase risk.
- Lifelong mental activity – Staying socially and mentally active may reduce risk.
Vascular dementia
This type of dementia is caused by injuries to the vessels that supply blood to the brain. It can be caused by brain damage from multiple strokes or any injury that blocks blood flow and deprives the brain of oxygen. Symptoms often begin suddenly and worsen in a stepwise manner. Vascular dementia accounts for about 10% of dementia cases.
Risk factors include high blood pressure, high cholesterol, heart disease, diabetes and smoking. Treating these conditions can help prevent further damage. Blood thinners after a stroke may help prevent additional small clots that lead to worsening dementia.
Dementia with Lewy bodies
This causes a progressive dementia and is one of the more common types. Abnormal deposits of the protein alpha-synuclein form inside nerve cells in certain areas of the brain. This process damages neurons that control functions like memory and movement. People may experience visual hallucinations. Parkinson’s disease is also marked by alpha-synuclein deposits. Dementia with Lewy bodies accounts for 10 to 25% of dementia cases.
Mixed dementia
Autopsy studies show that many people have evidence of more than one cause of dementia. Up to 45 percent of those diagnosed with Alzheimer’s disease also have some signs of vascular dementia. In many cases, Alzheimer’s disease and vascular dementia influence each other and cause symptoms to develop more rapidly.
Other conditions
There are numerous rarer causes of dementia, including:
- Parkinson’s disease
- Huntington’s disease
- Frontotemporal lobar degeneration
- Normal pressure hydrocephalus
- Prion diseases, including Creutzfeldt-Jakob disease
- Severe traumatic brain injury
- Substance abuse
- Infections like HIV, syphilis and chronic hepatitis
- Immune disorders
- Metabolic disorders like vitamin B12 deficiency
- Hypothyroidism
- Brain tumors
Some of these conditions are reversible if caught early. That’s why it’s important to have any sudden onset of dementia-like symptoms evaluated by a doctor.
What are the statistics on dementia?
Worldwide, around 50 million people have dementia. Here are some key facts about the prevalence of dementia globally:
| Statistic | Number |
|---|---|
| Estimated new cases per year | 10 million |
| Alzheimer’s disease cases | 60-80% of total |
| Cases under age 65 | 9% |
| Over age 85 | Between 25-50% |
The risk of dementia increases dramatically with age. It’s estimated that 3% of people between ages 65-74 have dementia, while nearly one third of those over age 85 are impacted.
An estimated 5.8 million Americans age 65 and older are living with Alzheimer’s dementia in 2022. Barring the development of medical breakthroughs to prevent, slow or cure Alzheimer’s disease, the number of people with it may nearly triple to 13.8 million by 2050.
Two-thirds of Americans with Alzheimer’s are women. Of the 5.8 million Americans over 65 with Alzheimer’s, 3.8 million are women and 2 million are men.
Why are more people being diagnosed with dementia?
Several factors are contributing to rising rates of dementia:
Aging populations
People over age 65 are at the highest risk. Increasing life expectancy means higher percentages of the population are now in the at-risk age bracket. The over 65 age group is growing faster than all other age groups around the world due to declining fertility rates and medical advances that prolong lifespan.
Increased detection
More people are being diagnosed at earlier stages thanks to greater awareness among patients and doctors and improved memory screening tools. People who would have simply been considered part of the normal aging process are now recognized as having early dementia.
Broader diagnostic criteria
The threshold for what is considered dementia has been lowered over time. Diagnosis used to require obvious cognitive impairment that made independent living difficult. Now even mild impairment is considered dementia.
Less stigma
In the past, many people avoided seeking medical attention for early dementia symptoms due to embarrassment or fear of being labeled. More open discussion has led to earlier diagnosis.
Higher disease burden
Conditions like obesity, diabetes and hypertension that increase dementia risk are on the rise. People today have more underlying disease that predisposes them.
Environmental factors
Increasingly sedentary lifestyles and less time spent on intellectually stimulating activities may also raise dementia risk for today’s aging populations.
Is dementia preventable?
Because dementia has so many causes, the strategies to prevent it vary. But research shows staying physically and mentally active, managing health conditions and maintaining social connections may all help lower risk.
Stay physically active
Regular exercise may directly benefit brain cells by increasing blood and oxygen flow. It also helps reduce heart disease and diabetes that can lead to dementia. Even modest amounts of exercise can make a difference.
Eat a healthy diet
A heart-healthy diet rich in fruits, vegetables and omega-3 fatty acids is associated with lower dementia risk. Avoiding obesity in midlife and limiting calories, saturated fat and simple carbohydrates as you age may also help protect the brain.
Manage health conditions
Controlling high blood pressure, diabetes and high cholesterol reduces the chances of developing vascular dementia. Quitting smoking prevents blockages. Treating sleep apnea improves oxygen levels.
Stay socially and mentally active
Interacting with others and challenging your mind builds cognitive reserve that allows the brain to operate despite damage. Pursuing hobbies, learning new skills, doing crossword puzzles or playing games may benefit brain health.
Check hearing
Hearing loss is linked to cognitive decline since it reduces stimuli to the brain. Treating hearing problems may help.
Prevent head injury
Reducing the chances of traumatic brain injury, especially repeated injuries, has been shown to lower future dementia risk.
While these steps can’t guarantee prevention, they may significantly reduce your changes of developing dementia as you age. Genetics and other factors outside your control also play a role. But living an overall brain healthy lifestyle gives you the best odds of protection.
Is there a cure for dementia?
There is currently no cure for the common irreversible causes of dementia like Alzheimer’s disease and Lewy body dementia. However, scientists are investigating multiple treatment strategies.
For Alzheimer’s, key areas of research include:
- Immunotherapy drugs – These work by clearing abnormal protein clumps from the brain.
- Tau-targeting drugs – They aim to stop the spread of tau tangles inside neurons.
- Neuroprotective drugs – These try to save neurons from damage and death.
- Lifestyle interventions – Diet, exercise and cognitive training may help slow progression.
So far, approved drugs only temporarily relieve Alzheimer’s symptoms for some people but don’t alter the course of the disease. However, there is hope emerging therapies in the pipeline may be able to stop or slow the damage Alzheimer’s causes.
For vascular dementia, the focus is on preventing additional strokes through blood thinners and controlling risk factors like high blood pressure. This can prevent further decline.
Some of the rarer causes of dementia like vitamin deficiencies, thyroid disorders and side effects of medications can sometimes be reversed with proper treatment. Even infections like syphilis can be cured with antibiotics to restore cognitive function.
While dementia cannot yet be cured or prevented in all cases, researchers are continuously developing better treatments. Lifestyle measures like exercise and cognitive stimulation may also help slow progression. There is hope emerging therapies will significantly change the long-term prognosis for those at risk.
Conclusion
Dementia is on the rise globally due to aging populations, improved detection, changing diagnostic criteria and higher prevalence of underlying risk factors like heart disease and diabetes. The most common causes, like Alzheimer’s disease and vascular dementia, cannot yet be cured or definitively prevented. However, controlling conditions like high blood pressure and high cholesterol may lower risk. Staying physically, socially and mentally active also benefits brain health as we age. Scientists are working aggressively on better treatments to stop or slow the progression of irreversible dementia. In the meantime, living an overall healthy lifestyle gives you the best shot at avoiding or delaying cognitive decline.