Verified answer

How about:

Today I'm going to speak about Insomnia. Insomnia is -- (pause) -- Well, I forget because I didn't sleep well last night.

Have fun!

It's probably best to explain what insomnia is first. E.g "Insomnia is a common problem which can effect people's health and wellbeing. Insomnia causes people to have trouble falling asleep or staying asleep for a long time. They may wake up during the night or wake up far too early the next morning."

Or alternatively you could begin with an interesting fact about insomnia to hook the audience in and make them want to hear more. For instance "More than 30% of the world's population suffer from insomnia, and one in every three people expirence insomnia at some point in their lifes."

Hope I helped