WASHINGTON — This is not your father’s Facebook. It’s your grandfather’s.

New data from the Pew Center for Internet and American Life released Monday show that Facebook’s strongest growth over the past year has come from users over the age of 65, as more older users sign onto the site to keep in touch with their friends, children and grandchildren.

The survey found that 45 percent of American seniors who use the Internet are on Facebook, up from 35 percent the previous year.

Use among teenagers, however, has stagnated at 84 percent. That’s in keeping with growing concern that Facebook is seeing lower engagement with the younger users that drove its early popularity, something that the company has acknowledged itself in an earnings call this year.

Facebook may be a victim of its own success after nearly 10 years as the country’s leading social network, said Pew senior researcher Aaron Smith.

“It’s hard to get more than 85 percent of anyone doing anything,” he said.