Malacanang admitted on Monday that President Rodrigo Duterte "struggled to be awake" during the Philippine Military Academy ( PMA) commencement exercises in Baguio City Sunday morning.

In a text message to reporters, Presidential Spokesperson Salvador Panelo made the explanation after Duterte allowed Defense Secretary Delfin Lorenzana to substitute for him during the distribution of certificates to the 261 graduates as he was just sitting on the chair trying not to fall asleep.

He also arrived late for the graduation rites.

"The event at 9 am was part of his sleeping time. He is a night person. He was so sleepy when he arrived at the venue. He struggled to be awake," Panelo said.

He noted Duterte usually sleeps at 6 am after working on papers, reading reports from various departments, and signing papers.

"He is a night person," he said.

Panelo explained that last Sunday, Dutere had to wake up at 8:30 am for the PMA graduation rites so he had only two hours sleep.

According to Panelo, also chief presidential legal counsel, the protocol in distributing the diplomas was either he did it himself or or he task the defense chief to do it.

"He (Duterte) opted to let SND (Secretary of National Defense) did the handing of the certificates. He reserved his energy for the other ceremonial acts he had to perform for the graduation rites," he explained.

"By the time, he delivered his speech, he was already in his usual alert, impassioned and assertive self," he added.

Netizens wondered if Duterte was okay during the PMA graduation rites.

Duterte's health has always been put in question, especially whenever he could not be seen in public for several days.

"To the people who wish him to be seriously ill, they will be disappointed. To those who are concerned about his well being, they should be assured that apart from what he already told the public of what ails him (which is not life threatening) the President is in good health, robust enough to be travelling to Japan for an official visit upon the invitation of Prime Minister Abe," he said.

Duterte will leave for Japan on Tuesday afternoon, two days ahead of the scheduled Nikkei forum on May 30 to 31. Celerina Monte/DMS