A study showed that the risk of developing dementia significantly increases in people aged 60 or older if they spend any amount of time sitting, such as watching TV or driving.
Professor David Raichlen’s team at the University of Southern California analysed the UK’s biomedical database in the Journal of the American Medical Association (JAMA) on the 13th and found that the risk of dementia significantly increases if you spend more than 10 hours a day sitting.
Professor Raichlen said that the total amount of time spent sitting per day, rather than the number or type of sitting behaviour, appeared to be associated with dementia, and that this was a notable result considering that Americans spend an average of 9.5 hours sitting per day.
“I know many people are told to break the habit of sitting for long periods of time by standing up or walking around every 30 minutes or so,” he said, explaining the background of the study, saying that sitting behaviour is associated with disease and mortality, but the relationship with dementia was not clear.
The research team analysed the association between sedentary behaviour and dementia risk using data measuring the movements of more than 100,000 adults 24 hours a day for a week with a wrist-worn accelerometer from the UK Biobank, a large biomedical database in the UK.
First, a machine learning algorithm was applied to the measurements of 49,841 people over 60 years old (average age 67.2 years) who were not diagnosed with dementia at the start of the study, and daily physical activity was measured by various factors such as sedentary behaviour and sleep. They were then followed up to see if they had been diagnosed with dementia for an average of 6.7 years using inpatient hospital records and death registration data, and 414 positive cases of dementia were discovered.
The research team reflected demographic characteristics that can affect brain health, such as age, gender, education level, chronic disease, genetics, race and ethnicity, and lifestyle characteristics such as physical activity, diet, smoking and drinking, and sedentary behaviour.
The association with dementia risk was statistically analysed. As a result, based on the median sitting time of 9.27 hours per day, the risk ratio (HR) for dementia rose sharply to 1.08 for people who sat for 10 hours, to 1.63 for 12 hours, and to 3.21 for 15 hours.
The adjusted dementia incidence rate per 1,000 person-years was 7.49 in the 9.27-hour group, 8.06 in the 10-hour group, 12.0 in the 12-hour group, and 22.74 in the 15-hour group, showing a significant increase as the sitting time increased.
In addition, it was confirmed that the average time spent sitting and maintaining posture along with the total time spent per day were significantly associated with the risk of developing dementia. However, the amount of time spent sitting did not seem to be related to the risk of developing dementia.
Co-researcher Gene Alexander, a professor at the University of Arizona, said, “This shows that the risk of dementia increases rapidly if sitting time exceeds 10 hours a day.” However, this also means that if you control your behaviour, such as not sitting for too long at a time, if you sit for less than 10 hours, dementia can be reduced.
“This study is part of our efforts to understand the impact of sedentary behaviour on brain health from a variety of perspectives,” said Professor Reichlen. “Research is needed,” he said.