People over the age of 60 who spend a lot of time seated are more likely to get dementia, a new study warns.
American researchers using UK data found that senior citizens who spend higher than average amounts of time sitting watching television or driving are at increased risk of developing the degenerative condition.
The study showed the risk of dementia ’significantly increases’ among adults who spend more than 10 hours a day sitting. Americans spend an average of 9.5 hours each day seated.
The study also revealed the way sedentary behaviour is accumulated over the course of the day didn’t matter as much as the total time spent sedentary each day.
Study author Professor David Raichlen explained that whether spent in extended periods spanning several hours or spread out intermittently throughout the day, total seated time had a similar association with 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 Professor Raichlen, of USC Dornsife College of Letters, Arts and Sciences.
‘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.’
Researchers used data from the UK Biobank database to investigate possible links between time spent seated and dementia risk.
More than 100,000 adults agreed to wear accelerometers, wrist-worn devices for measuring movement, for 24 hours per day for one week.
The research team focused on a sample of around 50,000 adults from the sub-study over the age of 60 who did not have a diagnosis of dementia at the outset.
The researchers then applied a machine-learning algorithm to analyse the large dataset of accelerometer readings and classify behaviour based on different intensities of physical activity.
The algorithm was able to discern between different types of activity such as sedentary behavior compared to sleeping.
The accelerometer data, combined with advanced computing techniques, provided researchers with a measure of the time spent engaged in different types of being seated.
After an average of six years of follow-up, the researchers used hospital records and death registry data to determine dementia diagnosis. They found 414 cases.
The team then adjusted their statistical analysis for age, sex, education level, race, chronic conditions, genetics and lifestyle characteristics – exercise, diet, smoking and alcohol use, self-reported mental health – that could affect brain health.
While large amounts of time spent sitting down were linked with increased risk of dementia, the researchers found that there were certain amounts of sedentary behaviour that were not associated with dementia.
‘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,’ said Professor Gene Alexander, of the University of Arizona.
‘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.’
Professor Raichlen added: ‘This should provide some reassurance to those of us with office jobs that involve prolonged periods of sitting, as long we limit our total daily time spent sedentary.’
The study, published in JAMA, builds on previous research, which used self-reported health data to investigate how certain types of sedentary behaviour – such as sitting and watching TV – affect dementia risk more than others.
‘Our latest study is part of our larger effort to understand how sedentary behaviour affects brain health from multiple perspectives,’ said Professor Raichlen.
‘In this case, wearable accelerometers provide an objective view of how much time people dedicate to sedentary behaviour that complements our past analyses.’
The team said further research is needed to establish whether physical activity can mitigate the risk of developing dementia.
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