Twitter is still growing in user numbers but it's not the young that are fueling this growth or the number of tweets. A new study from Nielsen confirms what has been speculated and mostly believed so far, namely that the vast majority of Twitter users are over 24 years old, with only 16 percent of the site's users being children, teenagers or young adults.

This comes after a rather anecdotal study from Morgan Stanley showed that young people weren't too keen on Twitter and had other interests in the social media environment, most notably Facebook. That study was written by a Morgan Stanley 15-year-old intern based on the preferences of his group of friends, which is not exactly representative or statistically accurate. But it's that study, and all the discussions it started, that spurred Nielsen to do proper research and come up with these latest numbers.

With data from the 250,000 US Internet users in its NetRatings panel the research firm found that growth was still strong, with the site reaching 10.7 percent of the entire web audience in June, but this growth came especially from the older age groups. In fact, those over 55, making up 20 percent of the twitterers, outnumber the young users. The largest part of Twitter users are aged between 25 and 54, though this age group is the biggest for Internet users in general. Still, young people make up 25 percent of the entire Internet audience but only 16 percent of Twitter's.

The numbers are only for the Twitter site and many are using third-party clients to keep up with the activity. Still, Nielsen claims that more than 90 percent of the popular client's TweetDeck audience is over 25 so the statistics may be accurate for all of Twitter's users not just the ones using the site.

However, the research firm believes that this doesn't actually affect Twitter so much as the site has never been really geared towards the younger audiences. “The fact remains that Twitter has grown to be a major online presence and is being driven forward by significant buzz. To illustrate this point: the volume of Twitter mentions on blogs, message boards and forums has reached the same level as Facebook, a property four times its size. We’ve also seen that Twitter’s growth is very highly influenced by buzz around current events such as the Iran election,” the researchers conclude.