By the year 2040, there will be 1.7 million people in the UK living with dementia, according to the latest concerning forecasts published in leading medical journal The Lancet.
As a result, many scientists view dementia as one of the leading public health challenges of the 21st century, due to the toll it places on patients, their families and the healthcare system.
However, experts remain optimistic that our growing understanding of dementia will allow us to increasingly prevent many of these cases, lead to new treatments, and help find better ways of managing dementia once people are diagnosed.
“Right now, the reality for people facing dementia is often years of hardship, stress and isolation,” says James Rowe, professor of cognitive neurology at the University of Cambridge. “But even today, there’s so much more that could be done. If we implemented the best practice knowledge that we have today, we would prevent about 40% of dementia.”
So what is dementia and what are the main causes?
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One of the most common misconceptions is that dementia is a single condition. Instead, neuroscientist Tara Spires-Jones, professor of neurodegeneration at the University of Edinburgh, describes dementia as a set of symptoms that can be caused by many different diseases.
There are thought to be at least 200 different dementias, of which the below five types are some of the most common:
While the underlying disease processes vary considerably from one dementia to another, they share many of the same risk factors that can predispose the brain to damage.
These include:
- Age
- Genetics
- Chronic inflammation
Research has shown that the ageing process is arguably the biggest of all dementia risk factors. For example, the number of people with Alzheimer’s disease, the most common form of dementia, doubles every five years beyond the age of 65. This is thought to be related to several age-related processes.
As we get older, different parts of our brain can atrophy or shrink in size, while our bodies become steadily more inflamed, often as a consequence of many years of unhealthy life choices. This chronic inflammation can progress through the bloodstream into the brain, where it causes damages to neurons and other types of brain cells.
Some people are also more vulnerable to developing a form of dementia due to their genetics. For example, inheriting two copies of a gene variant called Apolipoprotein E4 increases risk of developing the disease by between eight and 12 times compared with someone with no copies of this form of the gene. Likewise, genetics are thought to be behind a third of all cases of frontotemporal dementia.
Paresh Malhotra, a neurology professor at Imperial College London, says that research has linked mutations in genes with toxic protein deposition in the brain regions that are damaged in frontotemporal dementia. “That’s what’s killing the nerve cells in the brain, these abnormal protein deposits,” he says.
Risk factors include:
- Smoking
- Depression
- Excessive alcohol consumption
- Physical inactivity
- Type 2 diabetes
- Obesity
- Social isolation
The good news is that many of the risk factors can be taken under control, which will lessen your likelihood of getting dementia.
Quitting smoking is thought to be one of the most powerful strategies for lowering dementia risk, with current smokers found to be 30% more likely to develop some form of dementia. This is due to the damage that smoking can inflict on the heart and blood vessels over time, impacting blood flow to the brain.
Research published in the journal JAMA Neurology, which used data from more than 1.4 million people in Denmark, found that being diagnosed with depression as an adult can double your risk of dementia, possibly because damage that smoking can inflict on the heart and blood vessels over time
Traumatic brain injury, hearing impairment, hypertension and lower levels of education can all also increase dementia risk.
In 2023, newly published data from the Health and Retirement Study, an ongoing study of ageing in the US, found that greater exposure to PM2.5 air pollution was linked to dementia. In particular, pollutants released by agricultural processes and wildfires appeared to drive risk.
- Mild forgetfulness
- Difficulty with speech, writing clearly or communicating
- Change in personality
The early stages of different dementias can vary subtly from one disease to another. Spires-Jones says that in the early stages of Alzheimer’s disease, people often experience mild forgetfulness. “It’s things like memory and spatial memory, so where you put things and remembering what happened earlier in the day, where you put the car, that sort of thing,” she says.
However, in frontotemporal dementia, aphasia – a condition that affects the ability of the patient to speak and write clearly, and understand written words – is a common early sign. This is because the disease can damage a particular part of the brain called the temporal lobes. “They are more involved in speech, and they are one of the areas which stop working first,” says Malhotra.
As different dementias progress, many of the symptoms of cognitive decline begin to overlap more and more. “Dementias don’t just affect memory, they change personality, who we are as people in our relationships, how we can communicate, our ability with language,” says Rowe. “These are things that dementias affect, and different dementias do it in different ways to different extents.”
Types
Alzheimer’s is characterised by brain changes that lead to the accumulation of certain proteins, most notably amyloid, which clusters into plaques, and tau, which forms tangles. These protein deposits are toxic to the brain and drive both cell death and shrinkage of different brain regions.
Scientists are still trying to understand what triggers these hallmarks of the disease, and there are likely to be multiple causes. In many patients, the progression of Alzheimer’s is thought to be linked to the immune system waning with age, as well as changes in metabolism that affect how the brain processes fats, all of which contribute to neurodegeneration over time.
“There are multiple components to this complex disease, of which amyloid plaques is one,” says Julie Williams, a professor at Cardiff University who studies Alzheimer’s. “But it’s not the whole story.”
Having high cholesterol, elevated blood pressure and highly fluctuating blood sugar levels can all place the heart under stress, and over time this has a negative impact on the brain. This can happen through restricted blood flow due to partial or complete blood clots, which has a damaging effect on brain tissue.
“Cardiovascular disease and diabetes are two of the main contributing factors to the vascular changes in the brain that occur relatively late in life,” says Philip Scheltens, professor of neurology and founder of the Alzheimer Centre at Amsterdam University Medical Centres.
Scheltens points out that many dementia patients over the age of 75 will have a mixture of Alzheimer’s and vascular dementia. “Pure vascular dementia in itself is quite rare,” he says. “But the vascular contribution to Alzheimer’s disease is quite prevalent.”
Frontotemporal dementia is an umbrella term for a larger group of neurodegenerative diseases that all impact the frontal areas of the brain. While patients ultimately struggle with all aspects of cognition, the earliest signs are problems with speech, motivation as well as a loss of inhibition, all facets of behaviour that are controlled by the frontal brain regions.
Sarah Carter is a health and wellness expert residing in the UK. With a background in healthcare, she offers evidence-based advice on fitness, nutrition, and mental well-being, promoting healthier living for readers.
