Emperor Emeritus Akihito turned 91 years old on December 23.

He received visits from fellow members of the imperial family for birthday celebrations at his residence at the Akasaka Estate in Tokyo.

But his son Emperor Naruhito and his family canceled their visit as Princess Aiko was found to have come down with influenza.

The emperor and Empress Masako also refrained from paying a call on the retired emperor as a cautious measure.

Akihito has lived to the oldest age among Japan's historically documented emperors.

According to the Imperial Household Agency, the emperor emeritus has not shown any significant changes in his health.

He spends his days calmly with a structured routine while showing care for his wife Empress Emerita Michiko, who fractured her leg in a fall earlier this year.

Agency officials said Akihito refrains from talking while eating to prevent food from entering his lungs and watches TV for news on domestic and international developments.

He has particularly expressed concern about the Noto Peninsula in Ishikawa Prefecture, which experienced a powerful earthquake in January and torrential rains and flooding in September.