(CNN) -- Nancy Ehrlich was nearing 50 and frustrated, teaching at her small Pennsylvania town's elementary school with colleagues who didn't share her love of technology.

Then, last summer, she found Twitter.

Now, Ehrlich -- who turns 51 in a few weeks -- barely qualifies for the fastest-growing club on the Web. The number of internet users over 50 who use social-networking sites such as Facebook and Twitter have nearly doubled in the past year, according to a study released Friday.

"It definitely has changed my whole life -- that's how significant Twitter is to me," said Ehrlich, who now regularly chats with educators around the world and helps host a weekly forum for them on the micro-blogging site. "At first, I didn't really get it. But I just kept watching it and, before you knew it, I was hooked."

Between April 2009 and May, the percentage of internet users 50 and up who said they use social-networking sites has risen from 22 percent to 42 percent, according to the survey by the Pew Research Center.

Respondents 65 and older reported a 100 percent increase, while those between 50 and 64 jumped 88 percent.

Read More