U.S, Aug. 12 -- Tonight, millions of people in the world's fastest-growing megacities will lie awake in the dark. Not because they're caught in an addictive social media loop, but because their housing is a metal oven, the traffic outside their thin walls is deafening, and their alarm is set for 4:00 AM to catch a three-hour series of overcrowded buses.

We live in a culture obsessed with sleep hacks, smart mattresses, white-noise machines, and tracking rings. Yet we ignore a simple, uncomfortable truth: getting eight hours of quiet, uninterrupted rest has quietly become a luxury good.

In the developing world, sleep isn't just an individual health metric or a lifestyle choice. It is an invisible, structural fault line dividing those who ...