New data from the Pew Center for Internet and American Life show Facebook's strongest growth over the past year has come from users over the age of 65 as they join to keep in touch with their friends and family.

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 teens, however, has stagnated at 84 percent. That is in keeping with growing concern that Facebook is seeing lower engagement with the younger users that drove its early popularity.

A stagnating teen audience fits in with a recent study from researchers at University College London, which found some British teens are leaving Facebook for private messaging services such as WhatsApp and Snapchat because of the influx of older users.