Sitting this many hours a day ‘rapidly increases’ dementia risk, study warns

‘Findings should provide some reassurance to those of us with office jobs that involve prolonged periods of sitting’

Adults who spend a large part of their day engaging in sedentary behaviors are more prone to dementia, a new study finds.

The research, published on Monday in the journal JAMA, found that people aged 60 and older who spend over 10 hours a day engaging in behaviors like sitting while watching TV or driving could be at increased risk of developing dementia.

Scientists, including those from the University of Southern California say, the findings are concerning since Americans on average are sedentary for about 9.5 hours each day.

In the study, researchers assessed the data from about 50,000 adults over the age of 60 who had wrist-worn accelerometers to measure their movement for 24 hours per day for a week.

The individuals did not have a diagnosis of dementia at the start of the study, scientists noted.

They then used a machine-learning algorithm to analyse the dataset of accelerometer readings and classify behaviors based on different intensities of physical activity.

Using the AI system, scientists could differentiate between different types of activity and sleeping – providing an objective measure of the time each person spent engaging in different types of sedentary behaviors.

After an average of six years of follow-up, researchers used hospital records and death registry data to determine dementia diagnosis, and found 414 participants had the neurological condition.

Scientists then adjusted for factors such as age, sex, education level, race/ethnicity, chronic conditions, genetics as well as lifestyle characteristics like physical activity, diet, smoking and alcohol use, self-reported mental health.

They found that sedentary behavior was linked with increased risk of dementia among the participants.

However, they found that certain amounts of sedentary behavior was 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,” study author Gene Alexander from the University of Arizona said.

“This suggests that it is the total time spent sedentary that drove the relationship between sedentary behavior and dementia risk, but importantly lower levels of sedentary behavior, up to around 10 hours, were not associated with increased risk,” Dr Alexander added.

Researchers call for more studies to establish causality and whether physical activity can mitigate the risk of developing dementia.

The findings, according to scientists, “should provide some reassurance to those of us with office jobs that involve prolonged periods of sitting, as long as we limit our total daily time spent sedentary”.