People sitting down or being inactive as an older adult for more than 10 hours a day may be at increased risk of developing dementia, research suggests.
A study published in the journal Jama showed it did not matter whether the time spent sitting was over a long period or intermittently throughout the day as both had a similar effect on dementia risk.
The team said being inactive for fewer than 10 hours was not associated with increased risk of developing the condition, providing “some reassurance to those of us with office jobs that involve prolonged periods of sitting”.
“We were surprised to find that the risk of dementia begins to rapidly increase after 10 hours spent sedentary each day, regardless of how the sedentary time was accumulated," study author Prof Gene Alexander said.
“This suggests that it is the total time spent sedentary that drove the relationship between sedentary behaviour and dementia risk, but importantly lower levels of sedentary behaviour, up to around 10 hours, were not associated with increased risk.”
In England, adults of working age average about 9.5 hours a day of sedentary time.
This includes watching TV, using a computer, reading, doing homework and travelling by car, bus or train, but does not include sleeping.
Between the ages of 65 and 74, average sedentary time in men and women increases to 10 hours a day or more, according to figures from the British Heart Foundation.
For the study, the researchers looked at data from more than 49,000 people aged 60 and above from the UK Biobank, an online database of medical and lifestyle records of half a million people in Britain.
These people did not have dementia at the start of the study and were followed for more than six years, having been given devices to wear on their wrists to track movement.
Using a type of artificial intelligence known as machine-learning algorithms, the researchers classified different types of movement, including between sleeping and sitting still.
Mobility exercises to try at home - video
Over the course of the study, 414 people developed dementia.
When adjusting for lifestyle factors that could affect brain health – such as diet, smoking and alcohol use and self-reported mental health – and demographics such as age, sex, education level, ethnicity, chronic conditions and genetics, the team found that prolonged lack of movement was linked with increased risk of dementia.
“Many of us are familiar with the common advice to break up long periods of sitting by getting up every 30 minutes or so to stand or walk around," said Prof David Raichlen, also a study author.
“We wanted to see if those types of patterns are associated with dementia risk.
“We found that once you take into account the total time spent sedentary, the length of individual sedentary periods didn’t really matter.”
The authors say more research is needed to see if physical activity can reduce the risk of dementia.
Meanwhile, another study, published in the journal Jama Network Open, has found untreated high blood pressure to be associated with greater dementia risk.
The research, which was an analysis of data from 14 studies and involved more than 34,000 people aged 60 and above, showed that people with untreated high blood pressure had a 42 per cent increased risk of dementia compared with healthy people and 26 per cent increased risk compared with those who received treatment for the condition.