Replacing TV time with reading or desk work may lower dementia risk - medicalxpress

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New research distinguishing between passive and mentally active sitting in association with dementia has found that adults who engaged in extended durations of mentally passive sedentary behaviors had a higher risk of dementia. Replacing passive with mentally active sedentary behaviors was shown to reduce the risk of dementia onset in later life.

The study in the American Journal of Preventive Medicine, has the potential to inform public health guidelines and preventive strategies to reduce dementia.

Globally, populations are aging. Dementia is the third highest cause of mortality and the seventh largest cause of disability among older adults globally. It is a prevalent age-related condition affecting many adults' quality of life, including their families and caregivers. Prevention is important, and a key part of this involves identifying modifiable risk factors.

It was previously thought that all sedentary behaviors were associated with a higher risk of developing dementia. However, in recent studies, researchers found that mentally passive sedentary behaviors (such as watching TV) increased the risk of depression, while mentally active sedentary behaviors (such as reading and office work) appeared to be protective.

Most adults spend about nine to 10 hours per day sitting. Previous research has shown that extended, uninterrupted sitting is a risk factor for cardiovascular disease, type 2 diabetes, and depression. It has also been associated with dementia.

This is the first study to distinguish between passive and mentally active sitting in association with dementia.

Lead investigator Mats Hallgren, Ph.D., Department of Public Health Sciences, Karolinska Institute, Sweden, and Baker-Deakin Department of Lifestyle and Diabetes, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Australia, notes, "While all sitting involves minimal energy expenditure, it may be differentiated by the level of brain activity.

"How we use our brains while we are sitting appears to be a crucial determinant of future cognitive functioning and, as we have shown, may predict dementia onset."

Researchers analyzed data from a longitudinal study of 20,811 adults aged 35–64 years followed over 19 years (1997–2016). The baseline survey included questions about sedentary behaviors, physical activity, and other behaviors associated with dementia. Incident dementia was identified by linking the data of the 1997 survey with the Swedish National Patient Register and the Swedish Cause of Death Register.

Utilizing various statistical models, investigators examined the associations with dementia of (statistically) substituting passive with mentally active sedentary behaviors.

"The prospective study design allowed us to establish the direction of these relationships and infers but does not establish causality. Controlled trials are needed to confirm these important observational study findings," notes Dr. Hallgren.

The study's main findings are as follows:

• Mentally active sedentary behavior was associated with a reduced risk of developing dementia among middle-aged and older adults.
• Increasing time spent in mentally active sedentary behavior was associated with a significant reduction in dementia risk while maintaining the levels of passive sedentary behavior, light and moderate-to-vigorous physical activity.
• Replacing the amount of time spent in mentally passive sedentary behavior for equivalent durations of mentally active sedentary behavior was also associated with a reduction in the risk for developing dementia.

Given the extensive survey method used to collect these data (3,600 cities and villages across Sweden), the investigators believe the findings are likely generalizable to a wider global population.

Dr. Hallgren concludes, "Sedentary behavior is a ubiquitous but modifiable risk factor for many health conditions, including dementia. Our study adds the observation that not all sedentary behaviors are equivalent; some may increase the risk of dementia, while others may be protective. It is important to remain physically active as we age, but also mentally active—especially when we are sitting." 

Provided by Elsevier 

by Elsevier

edited by Sadie Harley, reviewed by Andrew Zinin 

Source: Replacing TV time with reading or desk work may lower dementia risk