Elon Musk has admitted that he listens to podcasts about the fall of civilization to help him get to sleep at night, despite it being one of his biggest worries.

"I listen to podcasts about the fall of civilizations to fall asleep," the billionaire Tesla boss said at the Milken Global Conference in Los Angeles on Monday.

Mr Musk was asked what keeps him up at night and responded, "Anything that's a civilizational risk," including plummeting birth rates and "anything that undermines the foundations of democracy in America or elsewhere" as well as "anything that's leading us away from a merit-based system."