Stroke patients who also suffer from an irregular heartbeat are at double the risk of developing dementia, according to a new study by the University of East Anglia (UEA).
Published tomorrow in the journal Neurology, the findings show that stroke survivors with an irregular heartbeat or atrial fibrillation - are 2.4 times more likely to develop dementia than stroke survivors without the heart condition.
The researchers analysed 15 studies with more than 45,000 participants and an average age of 72. They compared patients with and without atrial fibrillation, and followed up to determine which developed dementia over time. Around a quarter of patients with both stroke and atrial fibrillation were subsequently found to have developed dementia.
"These results offer convincing evidence of a link between irregular heartbeat and dementia in patients with stroke and could help us identify treatments that delay or even prevent the onset of dementia," said lead author Dr Phyo Myint of Norwich Medical School at UEA.
"Options include more rigorous management of cardiovascular risk factors or of atrial fibrillation, particularly in stroke patients."
The study is the first high-quality meta-analysis of the potential role of atrial fibrillation in the development of dementia. Though the results show a clear association in stroke patients, Dr Myint warned that signs of a link in the general population as suggested by some earlier studies were inconclusive.
"There remains considerable uncertainty about any link in the broader population," he said.
Atrial fibrillation is more common as people age. It affects around one in 20 people over 65 in the UK and more than two million in the US. The heart's two upper chambers do not beat effectively in the condition, resulting in an irregular heart rhythm. This can lead to blood pooling and clotting which significantly increases the risk of stroke. Around 15 per cent of strokes occur in people with atrial fibrillation. Other risk factors for stroke include smoking, high blood pressure and a sedentary lifestyle.
There are around 750,00O people with dementia in the UK and 60,000 deaths are attributed to the disease every year. The number of dementia cases is expected to rise by around 150 per cent over the next 40 years. The disease is little understood but the risk of developing dementia is thought to be multifactorial. Risk factors include older age, high blood pressure, diabetes and smoking.
Dr Myint said further high quality research was now needed to establish whether the link between atrial fibrillation and dementia in stroke patients was causal.
Dr Susanne Sorensen, head of research at the Alzheimer's Society, said: "This important research suggests that those with atrial fibrillation who have previously had a stroke need to be identified and monitored more closely. We now need more research involving stroke survivors with this type of cardiovascular disease to determine whether controlling atrial fibrillation with medication could reduce the risk of getting dementia later in life.
"Cardiovascular disease and stroke are well known risk factors for dementia. The best way to reduce risk of dementia is to take regular exercise, maintain a healthy weight, eating a healthy diet rich in fruit and vegetables and ensuring that your blood pressure and cholesterol are checked regularly."