TOKYO (AP) — Japan’s beloved former Emperor Akihito marked his 92nd birthday Tuesday as his heart condition stabilized, palace officials said, following health concerns earlier this year.

Akihito, the father of Emperor Naruhito, was diagnosed in May with insufficient blood flow to the heart muscles but has been in stable condition since he started a new medication in July, the Imperial Household Agency said in a statement.

He still enjoys scientific research into goby fish, career work in which he found 10 new species, and he visits a biology lab on the palace compound twice a week, the agency said.

Akihito, who has held the title of emperor emeritus since his abdication in 2019, was to celebrate his birthday with his family and receive guests, including Japanese Prime Minister Sanae Takaichi.

Known for his efforts to make amends for Japan’s wartime past, Akihito repeatedly prayed this year for its victims and the survivors who faced hardships as he marked the 80th anniversary of the end of World War II.

Akihito and his wife, Empress Emerita Michiko, offered a moment of silence on four key dates of the war 80 years ago — the end of the Battle of Okinawa, the atomic bombings of Hiroshima and Nagasaki, and the day marking Japan’s surrender — the IHA said.

He has said the war, fought in the name of his father Hirohito, should not be forgotten.

In August, Akihito and his wife visited a central Japan resort in Karuizawa, where he temporarily evacuated as a child during the war, and where the couple started a romance years later.