‘In Japan’s stormy summer of 1983, Ikuo Ishiyama couldn’t stop thinking about a chilling pattern among his patients. They were dead, but that wasn’t what troubled him. As a specialist in forensic medicine at Tokyo University, Ishiyama was accustomed to seeing dead bodies. However, these victims—numbering in the hundreds—shared a similar demise. “The symptoms are the same,” he told the Los Angeles Times. “Young men without medical problems are essentially dying in the same way, without warning.” What way was that? That may be the most mysterious detail: All of the victims died in their sleep.

Ishiyama’s concern grew when he heard about similar deaths halfway around the world, in the Midwestern and Western United States. There, they called it “nocturnal death syndrome,” but the circumstances were just as unsettling. “They passed away in the early hours of the morning,” the science journalist Alice Robb wrote in her book Why We Dream, “lying on their backs, with looks of horror in their eyes.” To this day, their exact cause of death is a mystery. But one University of Arizona anthropologist, who spent a decade studying the phenomenon, argued the victims suffered cardiac arrest due to what Robb describes as “stress, biology, and sheer terror.”

Were they victims of their nightmares?…’ (via Atlas Obscura )