Sedentary Behavior Linked to Higher Dementia Risk

Prolonged sedentary behavior such as watching TV or driving long hours may increase the risk of dementia in adults 60 and older.

Older adults who spend over 10 hours a day engaging in sedentary behaviors are at significantly higher risk of developing dementia, according to a study conducted by researchers at the University of Southern California (USC) and the University of Arizona.

Previous research suggests that getting up every 30 minutes to move your body may lessen the harmful health impacts of prolonged sitting. However, when it comes to dementia, the total time spent sedentary each day matters more than the way sedentary behavior is accumulated over the course, the study that appeared in JAMA suggests.

"We found that once you take into account the total time spent sedentary, the length of individual sedentary periods didn't really matter," study author David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences, said in a statement.

The researchers examined data from about 50,000 adults from the U.K. Biobank sub-study who were over 60 and did not have a diagnosis of dementia at the start of the study. The participants wore accelerometers, wrist-worn devices for measuring movement, for 24 hours per day for one week.

Using a machine-learning algorithm, the researchers analyzed the large dataset of accelerometer readings and classified behaviors based on different intensities of physical activity. This allowed researchers to measure how much time the participants spent in different sedentary behaviors.

After an average of six years of follow-up, 414 participants were diagnosed with dementia.

While a sedentary behavior was associated with an increased risk of dementia, the researchers note that those who spend less than 10 hours a day sitting are not at higher odds of developing the condition.

"This 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," said Raichlen.

Previous research from the same team found that only passive sedentary activities, such as watching TV, were associated with a higher risk of dementia, even in physically active individuals. Additionally, sedentary time spent actively, such as using a computer, was linked to reduced dementia risk. The researchers said greater intellectual stimulation may counteract the negative effects of sitting.

Risks of sedentary behavior

The average American spends about 9.5 hours sitting each day.

Leading a sedentary lifestyle increases the risk of a wide variety of conditions, such as:

• Cardiovascular disease
• Type 2 diabetes
• Obesity
• Colon cancer
• High blood pressure
• Osteoporosis
• High cholesterol levels
• Depression and anxiety

According to the Physical Activity Guidelines for Americans, adults should do at least 150 minutes a week of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity, preferably spread throughout the week.

Moderate-intensity aerobic activity includes brisk walking (4 mph), light cycling (10 to12 mph), recreational badminton, and tennis doubles. Meanwhile, examples of vigorous aerobic activity are hiking, jogging at 6 mph, fast cycling (14 to 16 mph), basketball and soccer games, and tennis singles.

More than six million Americans are living with Alzheimer's disease, the most common form of dementia, and this number is projected to rise to nearly 13 million by 2050. While aging is the biggest risk factor for dementia, engaging in physical activity may help to reduce the odds of developing the condition.