Michiko, the wife of Emperor Akihito, said in a pre-birthday statement that she is well taken care of by her palace doctors and, when necessary, outside specialists.

She has in the past suffered from ailments believed to be related to stress, and has recently shown signs of a form of asthma.

“I myself have been blessed with relatively good health, but in the last few years I feel I have become a lot slower at doing things,” she said. “I also often experience symptoms that seem to be caused by aging, such as not being able to find what I am looking for. I find these incidents amusing at times, but I also feel a bit helpless.”

The royal couple assumed the Chrysanthemum Throne 21 years ago, after the death of Akihito’s father, the late Emperor Hirohito.

In their official role as symbolic figureheads, they carry out a wide range of duties, from welcoming foreign dignitaries to bestowing awards and observing palace rituals and ceremonies. They have, however, recently kept a somewhat lower public profile than in past years.

In modern Japan, monarchs generally do not abdicate the throne. After their coronation, they reign for the rest of their life.