TOKYO: Japan's Empress Michiko is suffering from a stomach problem, the palace said Monday, in the latest health condition expected to slow down the schedule of the imperial couple.

The 73-year-old wife of Emperor Akihito is suffering from gastroesophageal regurgitation, a condition in which stomach fluid flows backward into the esophagus, the Imperial Household Agency said.

The disease often causes heartburn and is thought to be triggered by stress or other factors such as the tightening of the body by kimono sash, the agency said.

The empress is taking medicine to reduce gastric acid when necessary and she has not suffered inflammation in the esophagus, it said.

The empress has been experiencing dull pains in her chest and back and coughing for a few years and she was diagnosed with the disease on the basis of an endoscopic examination in January.

The agency said it might advise Michiko to reduce her official duties such as court ceremonies after further studies of her condition.

Last month, the agency said that 73-year-old Emperor Akihito was showing early signs that might lead to the bone-thinning disease osteoporosis.

Chief palace doctor Ichiro Kanazawa said at that time that the palace was considering reducing the emperor's duties, or adjusting his lifestyle to prevent his bones' deterioration.

The imperial couple hold a ceremonial role in Japan and are constitutionally barred from any political involvement. - AFP/ac