Empress Emerita Michiko has been in poor health since mid-September, vomiting multiple times and losing weight, with stress seen as one of the possible causes, the Imperial Household Agency said Friday.

The 85-year-old former empress underwent breast cancer surgery in early September and has since been receiving hormonal treatment. The agency said post-surgery treatment is not suspected to be behind her vomiting, which included a small amount of blood.

She was also found to have a cardiac valve abnormality and irregular pulse during a checkup in June to probe a rise in levels of heart failure markers. The levels remain high and doctors are monitoring her condition, the agency said.

The former empress and her husband, Emperor Emeritus Akihito, have been receiving health checks twice a year and are scheduled to undergo this year’s second round later this month. But the agency said doctors will conduct tests whenever necessary.