According to the NHS, vascular dementia is a common type of the condition, which is estimated to affect around 150,000 people in the UK.
The illness is caused by reduced blood flow to the brain, which damages and eventually kills cells – and this is where the link between stroke and dementia comes into play.
The reduced blood flow that occurs in dementia patients is usually caused by either a single stroke, where supply is suddenly cut off, or lots of “mini-strokes” that cause tiny but widespread damage to the brain.
When the brain tissue starts to die, this is when we can begin to see problems with memory, reasoning, judgement, planning and other processes.
It’s believed that almost a quarter of people who have had a stroke will go on to develop vascular dementia, according to the Alzheimer’s Society.
This usually occurs around three to six months after the incident occurs – though the NHS notes that in some cases the dementia can start immediately after.
But while studies have been able to suggest that there is a link between stroke and cognitive impairment such as dementia for a number of years, researchers had been unable to quantify the degree to which stroke increased the risk.
That was until a team at the University of Exeter Medical School found that people who have had a stroke are around twice as likely to develop dementia.
The study – which was the largest of its kind ever conducted at the time, in 2018 – analysed data on stroke and dementia risk from 3.2 million people across the world.
The link between stroke and dementia persisted even after taking into account other risk factors, such as blood pressure, diabetes and cardiovascular disease.
The findings give particularly strong evidence that having a stroke significantly increases the risk of dementia.
A comprehensive review of post-stroke dementia (PSD) in 2017 had similar findings: PSD may affect up to one third of stroke survivors.
And, unfortunately, the same review noted that “as treatment strategies to inhibit the development and mitigate the course of PSD, lowering of blood pressure, statins, neuroprotective drugs, and anti-inflammatory agents have all been studied without convincing evidence of efficacy.
“Lifestyle interventions, physical activity, and cognitive training have been recently tested, but large controlled trials are still missing.”
But what makes that one third different to other stroke survivors?
According to an Alzheimer’s Society research project, previous work has shown that there is an area inside the front part of the brain where bundles of cell fibres, known as ‘white matter’, are particularly vulnerable to damage.
It’s been shown that those who did develop dementia after stroke are more likely to have blood vessels that are showing signs of leaking in this area, whereas those who weren’t faced with the condition did not have leaky vessels in the same region.
However, research to date has not been able to explain why some people’s brains are unable to contain this leaking – which may prevent dementia – and others aren’t.
It has been noted by Mayo Clinic that whether a stroke affects your thinking and reasoning can depend heavily on its severity and location.
And contradictory to the 2017 review, Mayo also believes that factors that increase your risk of stroke – including diabetes, high blood pressure, high cholesterol and smoking – may also raise your post-stroke vascular dementia risk, while controlling these factors can lower chances.
The number of strokes a patient has suffered is also likely to play a part in their chances of developing PSD.
In a 2012 study, one researcher reviewed nine studies on dementia in people who had had one stroke and found that rates of PSD were between 9.6 and 14.4 per cent. The rate increased, however, to 29.6 to 53.1 per cent in those with recurrent stroke.
The same project further determined that the two are closely entwined – stroke is a risk factor for dementia, and dementia is a risk factor for stroke.
The most common early symptoms of vascular dementia include difficulty concentrating, planning, organising and making decisions, slowed thought processing, and trouble following instructions.
It’s also common to see changes within the patient’s emotional wellbeing, such as depression, anxiety and apathy. However, it’s worth noting that changes to mood are not always good indicators.
It’s not unusual for mental health to suffer in stroke patients, so don’t be alarmed if your loved one shows these symptoms, as they’re not exclusively linked to vascular dementia.
Even before considering the risk of vascular dementia, it can be tough for family, friends and loved ones of stroke survivors to care for them as they try to recover.
The Stroke Association offers a number of informative leaflets and information packs on supporting a stroke survivor, which can be downloaded here.
The NHS also provides guidance on the physical, psychological and cognitive impact of a stroke here.
