Researchers asked 18,154 adults between the ages of 50 and 65 who did not have dementia if they "regularly use the World Wide Web, or the Internet, for sending and receiving e-mail or for any other purpose, such as making purchases, searching for information, or making travel reservations?”

After eight years tracking the adults, people who used the internet at the start of the study had about half the risk of dementia as people who were not regular users.

The researchers also looked at how often these adults were online, from not at all to more than eight hours a day. Those who used the internet for about two hours or less a day had the lowest risk of dementia compared to those that didn’t use the internet, who had a “notably higher estimated risk.” The researchers also found that people who were online six to eight hours a day had a higher risk of dementia, but that finding wasn’t statistically significant, they said, and more research is needed.

“Online engagement may help to develop and maintain cognitive reserve, which can in turn compensate for brain aging and reduce the risk of dementia,” study co-author Dr. Virginia W. Chang said.

Currently, about 6.2 million people in the country over the age of 65 have Alzheimer’s disease, the most common form of dementia, the U.S. Centers for Disease Control and Prevention said.