Sitting or lying down for long periods of time may increase the risk of developing Alzheimer's disease, regardless of physical activity level, a new study suggests.
Experts have long recommended 150 minutes of physical activity per week to combat the risks that come from sedentary work or spending time in front of the TV.
But research from Vanderbilt University Medical Center in Nashville claims that being active in your free time doesn't necessarily help prevent Alzheimer's.
The study showed that, regardless of how much exercise a person did, those who spent more time sitting or lying down each day performed more poorly on cognitive tests and had brain shrinkage associated with Alzheimer's disease.
In the study published in the journal Alzheimer's & Dementia: The Journal of the Alzheimer's Association, scientists followed over 400 adults over the age of 50.
The participants, who had no symptoms of dementia, wore a smartwatch that measured their activity level for a week.
This data was used to estimate their average level of physical activity.
The results were then compared with cognitive function tests and brain scans performed over the next seven years.
Those who spent more time sedentary were more likely to show symptoms of Alzheimer's - regardless of their level of physical exercise.
Also, greater shrinkage was observed in the hippocampus area - a part of the brain essential for memory and learning.
While this area naturally shrinks with age, this process is accelerated in people with Alzheimer's.
These results were observed despite about 90% of participants meeting the recommendation of 150 minutes of exercise per week.
Scientists found that the risk from a sedentary lifestyle was particularly high in those with the APOE-e4 gene, a genetic factor that increases the chance of developing Alzheimer's.
This gene is found in about one in 50 people, including the famous "Avengers" actor, Chris Hemsworth, and has been linked to a tenfold higher risk of developing Alzheimer's.
The study authors suggested that those with the APOE-e4 gene should take additional measures to reduce the time spent sitting.
Lead author, Dr. Marissa Gogniat, said the results show the importance of avoiding prolonged sitting, even if you are physically active.
“Reducing the risk of Alzheimer's disease is not just about one workout a day,” she said.
"Minimizing time spent sitting, even if you exercise every day, reduces the chance of developing Alzheimer's."
Professor Angela Jefferson, co-author and expert in neurology, added:
"This study highlights the importance of reducing sedentary time, especially in older adults who are at increased risk due to genetic factors."
"It is essential for brain health to take breaks from sitting during the day and move around to increase physical activity time."
While the study can't pinpoint exactly how sitting contributes to the increased risk of Alzheimer's, they do have a theory.
Being sedentary for long periods can interrupt normal blood flow to the brain, and over time this can lead to structural changes that contribute to the development of the disease.
Alzheimer's is the most common cause of dementia in the UK.
A recent analysis by the Alzheimer's Society in Britain estimated that the total annual cost of dementia in the country is around £42 billion, with families bearing the brunt of the burden.
With the population ageing, this cost is expected to reach £90 billion over the next 15 years.
Around 944,000 people in the UK are believed to be living with dementia, while in the US this number is around seven million.
Alzheimer's is thought to be caused by the toxic buildup of proteins in the brain, which become an obstacle to its normal functioning.
The brain tries to cope with the damage, but symptoms of dementia develop over time.
Problems with memory, thinking, reasoning, and difficulties with language are common early symptoms, which worsen over time.
An analysis by Alzheimer's Research UK showed that 74,261 people died from dementia in 2022 – compared to 69,178 the year before – making it the biggest cause of death in the country. /Express newspaper/
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