Police arrested a male nurse Thursday on suspicion of causing injury resulting in the death of an 89-year-old patient at a hospital in Matsudo, Chiba Prefecture, in January.
Ryoichi Kawaguchi, 26, a former assistant nurse at Shin-Matsudo Central General Hospital, was arrested on suspicion of striking the woman with his hand at around 9 a.m. on Jan. 4, police said.
Kawaguchi, a resident of Saitama, was fired Jan. 30.
The woman, who was suffering dementia, was allegedly struck in the face. She later suffered a brain hemorrhage and died Jan. 23, they said.
The woman, who had been hospitalized after suffering complications from a blood disease, was in a room for patients with dementia at the time of the incident, they said.
Although an autopsy determined the direct cause of death to be pulmonary edema, police said the man's action had aggravated her condition, leading to her death.
Kawaguchi admitted striking the woman, saying "she was behaving badly," police and hospital officials said.
The hospital reported the incident to police on Jan. 6 after another nurse noticed bruises on the woman's face.
"(The incident) was extremely regrettable," said Toshiyuki Onoda, secretary general of the hospital.
"We have reported the case to the authorities and we cannot comment further at this point."
Shin-Matsudo Central General Hospital is one of the largest medical institutions in the city, equipped with 283 beds for inpatients.