Sitting or lying down for long periods could increase your risk of Alzheimer’s regardless how much exercise you do, a study has suggested.

Experts have long recommended 150 minutes of weekly workouts to help combat the health risks of desk-bound jobs and watching television.

But research from the Vanderbilt University Medical Center in Nashville claims being active during leisure time doesn’t help prevent Alzheimer’s.

Research has shown that even if someone engages in regular physical activity, spending extended periods sitting or lying down can lead to poorer performance in cognitive assessments and is associated with brain shrinkage linked to Alzheimer’s disease.

In the study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, scientists tracked more than 400 adults aged over 50.

The participants, who were dementia-free, were asked to wear a watch that measured their activity levels for a week.

Scientists used this to gauge how active they were on average.

These results were then compared to cognitive performance tests and brain scans conducted during the next seven years.

The scientists found the risk was particularly high for people carrying the APOE-e4. This gene, carried by the likes of Avengers star Chris Hemsworth, has been linked to a ten-fold increased risk of Alzheimer’s 

Those with more sedentary time were more likely to experience Alzheimer’s symptoms – regardless of how much they exercised.

They also saw greater reduction in the size of their hippocampus, part of the brain  crucial to memory and learning.

While this area shrinks normally as we age, this process accelerates among those with Alzheimer’s.

These results were observed despite almost nine in ten completing the 150 minutes of recommended exercise per week. 

The scientists found the risk posed by sedentary time was particularly high for those with the APOE-e4 gene, a genetic risk factor for Alzheimer’s.

APOE-e4 is carried by about one in 50 people, including the likes of Avengers star Chris Hemsworth, and has been linked to a ten-fold increased risk of Alzheimer’s.

The authors suggested those with the APOE-e4 gene may want to take extra measures to reduce their sedentary time.

Alzheimer’s is the most common cause of dementia. The disease can cause anxiety, confusion and short-term memory loss

Lead author Dr Marissa Gogniat said the results demonstrated the importance of avoiding sitting for long periods, even if you are otherwise fit and active.   

‘Reducing your risk for Alzheimer’s disease is not just about working out once a day,’ she said.

‘Minimising the time spent sitting, even if you do exercise daily, reduces the likelihood of developing Alzheimer’s disease.’

Professor Angela Jefferson, fellow author and expert in neurology, added: ‘This research highlights the importance of reducing sitting time, particularly among ageing adults at increased genetic risk for Alzheimer’s disease.

‘It is critical to our brain health to take breaks from sitting throughout the day and move around to increase our active time.’

While the study cannot pinpoint exactly how time spent sitting increases Alzheimer’s risk, they posed a theory.

Being sedentary for long periods may disrupt the healthy flow of blood to the brain, and over the long term this could lead to structural changes in the organs that contribute to Alzheimer’s. 

Around 900,000 Britons are thought to have the memory-robbing disorder. But University College London scientists estimate this will rise to 1.7million in two decades as people live longer. It marks a 40 per cent uptick on the previous forecast in 2017

Alzheimer’s is the most common cause of dementia in the UK. 

A recent analysis by the Alzheimer’s Society estimated the overall annual cost of the dementia to the UK is £42billion a year, with families bearing the brunt. 

An ageing population means these costs – which include lost earnings of unpaid carers – are set to soar to £90billion in the next 15 years.

Around 944,000 in the UK are thought to be living with dementia, while the figure is thought to be around seven million in the US.

Alzheimer’s is thought to because by a toxic build-up of proteins in the brain, which clump together to make it harder for the organ to work properly.

The brain struggles to cope with this damage and dementia symptoms develop.

Memory problems, thinking and reasoning difficulties and language problems are common early symptoms of the condition, which worsen over time.

Alzheimer’s Research UK analysis found 74,261 people died from dementia in 2022 compared with 69,178 a year earlier, making it the country’s biggest killer.