Twitter is not just for kids, according to a new ComScore study. The number of people using Twitter in February jumped a dramatic 700 percent compared to the same month last year, reported ComScore.

And who's largely behind that huge increase? Well, it's not the teen set. It's not even twenty-somethings or thirty-somethings, according to the online researcher. Comscore found that people between 45- and 54-years-old are 36 percent more likely than other age groups to use Twitter, making them the highest rated age group, followed by 25- to 34-year-olds, who are 30 percent more likely to Tweet out updates about their life and work.

Overall, worldwide visitors to Twitter were close to 10 million in February, noted Sarah Radwanick, a blogger for comScore.

What's notable about this is that traditionally, the people who first populate social networking sites - think MySpace and Facebook - are younger.

But older users are now diving into social networking. Just last month, Hitwise, which measures online traffic, reported that Facebook's audience of people over 35 increased by 23 percent in February compared to February 2008. While the social network was launched to serve students in the US, Facebook has broadly expanded that audience over the past year to include many middle-aged people.

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