How Extended Sitting Time May Be Aging Your Brain Faster
By UNIVERSITY OF SOUTHERN
CALIFORNIA
.webp)
Their study showed the risk of dementia significantly
increases among adults who spend over 10 hours a day engaging in sedentary
behaviors like sitting — a notable finding considering the average American is
sedentary for about 9.5 hours each day.
The study, published on Tuesday, September 12 in JAMA, also revealed the way sedentary behavior is accumulated over the course of the day didn’t matter as much as the total time spent sedentary each day. Whether spent in extended periods spanning several hours or spread out intermittently throughout the day, total sedentary behavior had a similar association with dementia according to study author David Raichlen.
Research Methods and Findings
“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. 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,”
said Raichlen, professor of biological sciences and anthropology at the USC Dornsife
College of Letters, Arts and Sciences.
Researchers used data from the U.K. Biobank, a
large-scale biomedical database of participants across the United Kingdom, to
investigate possible links between sedentary behavior and dementia risk.
As part of a U.K. Biobank sub-study, over 100,000 adults
agreed to wear accelerometers, wrist-worn devices for measuring movement, for
24 hours per day for one week. The researchers focused on a sample of
approximately 50,000 adults from this sub-study over the age of 60 who did not
have a diagnosis of dementia at the start of the study.
The researchers then applied a machine-learning algorithm to analyze the large dataset of accelerometer readings and classify behaviors based on different intensities of physical activity. The algorithm was able to discern between different types of activity such as sedentary behavior versus sleeping.
The accelerometer data, combined with advanced computing techniques,
provided researchers with an objective measure of the time spent engaging in
different types of sedentary behaviors.
After an average of six years of follow-up, the
researchers used inpatient hospital records and death registry data to
determine dementia diagnosis. They found 414 cases positive for dementia.
Then, the team adjusted their statistical analysis for
certain demographics (e.g., age, sex, education level, race/ethnicity, chronic
conditions, genetics) and lifestyle characteristics (physical activity, diet,
smoking and alcohol use, self-reported mental health) that could affect brain
health.
Total time spent sedentary each day drives dementia risk
While high amounts of sedentary behavior were linked with
an increased risk of dementia, the researchers found that there were certain
amounts of sedentary behavior 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. 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,” said study author Gene
Alexander, professor of psychology and psychiatry at the Evelyn F. McKnight
Brain Institute at the University of Arizona and Arizona Alzheimer’s Disease
Research Center.
“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,” said Raichlen.
The study builds on their previous research, which used
self-reported health data to investigate how certain types of sedentary
behavior, like sitting and watching TV, affect dementia risk more than others.