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  has the potential to inform public health guidelines and preventive strategies to reduce dementia, according to the authors.

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.

“While all sitting involves minimal energy expenditure, it may be differentiated by the level of brain activity," commented lead author Mats Hallgren, PhD, of the Karolinska Institute, Sweden. "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 ages 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.

Using various statistical models, investigators examined the associations with dementia of substituting passive with mentally active sedentary behaviors. 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 authors believe the findings are likely generalizable to a wider global population. However, they caution that the study infers but does not establish causality.

To download the full article, published in the American Journal of Preventive Medicine, click here