Zlatko Glusica was the captain of an Air India Express plane carrying 166 passengers from Dubai to Mangalore, a bustling port city on India's southern coast. As his Boeing 737 approached the city, Mr. Glusica woke up from a nap in the cockpit and took over the controls. His co-pilot warned him repeatedly that he was coming in at the wrong angle and that he should pull up and try again. The last sound on the cockpit recorder was the co-pilot screaming that they didn't have any runway left. The plane overshot the landing and burst into flames. Only eight people survived. An investigation found that the captain was suffering from "sleep inertia."

It isn't just the airline industry. Some 20% of automobile accidents come as the result of drowsy drivers, according to the Centers for Disease Control and Prevention. U.S. military researchers, meanwhile, have concluded that sleeplessness is one of the leading causes of friendly fire.

Sleep wasn't something we were supposed to worry about in the early years of the 21st century. Technology was making the world smaller by the day; the global economy blurred the lines between one day and the next, and things like time and place were supposed to be growing ever less important in the always-on workplace. Most of us never gave sleep much thought—considering it nothing more than an elegant on-off switch, like the ones on our smartphones, that the body flips when it needs to take a break from its overscheduled life. Sure, we'd like to get a bit more of it. But, beyond that, sleep likely hovers somewhere near flossing in most of our lives: something we are supposed to do more—but don't.

Americans, however, are starting to wake up about sleep. Endless ads for dubious energy drinks and an equal number of much slicker ads for prescription sleep aids reveal a culture in 2012 that is wired and tired. Lack of sleep, it seems, has become one of the signature ailments of our modern age.