You may not be surprised to know that way, way, way back in the day people had longer attention spans. Really, you don't even have to go that far back. In 1863, when Abraham Lincoln delivered the Gettysburg Address, people routinely gave two-hour speeches and people actually listened. So when Lincoln concluded after just two minutes, no one applauded because they didn't realize he was done.
Interesting, huh? And slightly topical seeing as Lincoln's birthday was a week ago.
Real Simple has an article about how to improve your attention span.
I don't know that you'll be successful to the extent of being able to listen to two-hour speeches, but I can vouch for sleep. It makes a huge difference. My rambly post yesterday about the Real Housewives? Definitely a result of a short attention span which was a direct result of having only five hours of sleep.
(Cheers to Real Simple)