Sedentary behaviours, such as sitting while watching television or using a computer, have become increasingly common among the population. Previous studies have shown that sedentary-type activities are linked to various health problems (e.g. cardiovascular problems). However, the association between sedentary behaviour and the risk of different subtypes of dementia (i.e. all-cause dementia) in older adults remains unclear. In a new study published in JAMA, a team of researchers led by Dr David A. Raichlen from the University of Southern California (Los Angeles, US) gathered data from the UK Biobank and collected, using an accelerometer, measurements associated with body movements from 49,841 adults residing in Wales, Scotland, or England, aged 60 years or older, and who did not have a dementia diagnosis when they first wore the accelerometer.
All the participants agreed to wear an accelerometer for 24 hours per day for seven days on their dominant wrist. All of them were also followed up from the time the accelerometer was first worn (from 2013 to 2015) until they were either diagnosed with dementia, died, were lost to follow-up or until the last date of hospital admission (2021 in England and Scotland, and 2018 in Wales). After collecting seven days of wrist accelerometer information, the team of researchers analysed the daily average duration of sedentary behaviour (hours per day), the average length and the maximal length of daily sedentary bouts, and the mean number of sedentary bouts per day (sedentary bouts were described as more than two consecutive 30-second epochs categorised as waking sedentary behaviours).
During the time participants were followed up (almost seven years), 414 cases of incident all-cause dementia were identified. During this time, the team of researchers also found that there is a significantly positive association between the duration of sedentary behaviour (an average of 10 hours per day or more) and incident all-cause dementia in adults aged 60 years or older. The study findings are in line with previous research and indicate that increased time spent on sedentary-type activities may be linked to lower cognitive performance and increased dementia risk. However, more research is needed to investigate whether this link is causal.