Brigitte Steger, a Cambridge University lecturer in Japanese studies, said the preoccupation with awakening early, last seen in Japan during the first half of the 20th century, might be a "conscious and coordinated attempt" to foster national identity.

Steger notes recent Japanese governments have taken similar steps, including requiring schools to teach students how to be patriotic. Steger argues the fad for early rising is a more subtle manifestation of the same trend.

"The key reason for the revival in early rising culture is that it teaches people to control their emotions, feelings and desires," said Steger. "It is training in spiritual determination so people feel motivated to contribute selflessly to a common cause.

"That cause can often be economic, but there are clear signs that many of these movements encourage people to take pride in their country and the part they play in Japanese life. In some ways, they are being urged to overcome their own spiritual weaknesses and replace them with nationalist pride."

Her findings appear in a new book, "Worlds of Sleep," which Steger co-edited.