For years, researchers have believed prolonged sitting could raise dementia risk — but new findings suggest what you do while sitting may matter more than previously thought.

The research, which was published in the American Journal of Preventive Medicine in March, found that replacing mentally passive sedentary behavior with mentally active sedentary behavior was associated with a significant reduction in dementia risk.

Mentally active sedentary behaviors could include reading, office work and other activities that keep the brain engaged while sitting, while mentally passive behaviors may include watching television or other low-engagement screen activities.

To gather the findings, Swedish researchers analyzed data from more than 20,000 adults between ages 35 and 64 who were tracked over a 19-year period, between 1997 and 2016, according to a press release.

Participants answered questions about their sitting habits, physical activity and other lifestyle behaviors, while dementia diagnoses were identified using Swedish health and death records.

Mentally active sedentary behavior was associated with “a significant reduction in dementia risk” compared to more passive sitting activities.

Although the study was based in Sweden, the release said the findings “are likely generalizable to a wider global population” and could help “inform public health guidelines and preventive strategies to reduce dementia.”

In a statement, lead researcher Dr. Mats Hallgren of Sweden’s Karolinska Institute said the study highlighted major distinctions between passive and mentally engaging sedentary habits when it comes to brain health.

“While all sitting involves minimal energy expenditure, it may be differentiated by the level of brain activity,” said Hallgren.

“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.”

Sedentary behavior is a “ubiquitous but modifiable risk factor for many health conditions, including dementia,” according to the researcher.

“Our study adds the observation that not all sedentary behaviors are equivalent; some may increase the risk of dementia, while others may be protective,” he added. “It is important to remain physically active as we age, but also mentally active — especially when we are sitting.”

The CDC projects that by 2060, nearly 14 million American adults will have Alzheimer’s disease.

One recent study published by the Alzheimer’s Association found that a person’s biological age may be tied to dementia risk.

Researchers also recently found that a higher intake of unprocessed meat may protect against dementia in older people who have a variant of a certain gene.