• Chunichi Shimbun


Research conducted by Atsushi Okada from the nephro-urology department at Nagoya City University Graduate School and others has revealed that the risk of kidney stone disease increases for astronauts who remain in space for a long period of time because diminishing bone mass triggers a rise in calcium levels in urine.

However, the researchers also discovered that the malady, which causes severe pain in the upper and lower back, can be prevented by ingesting a therapeutic agent used to treat osteoporosis before taking flight.

The professor hopes their latest finding will improve the health of astronauts and ensure their safety.

According to Okada, astronauts who stay in space — where they are less subject to the forces of gravity — are in a similar state to those who are bedridden. Their bones weaken easily due to reduced stress, leading to bone loss and calcium oxalate crystals in urine that develop slowly to form urinary stones.

This risk was first identified in the 1960s when the U.S., Russia and other countries received reports of its occurrence during space flight or after the astronauts returned to Earth. If even one member develops kidney stones during a mission the astronaut will have difficulty completing required tasks, and this could jeopardize the lives of all astronauts on board.

When the human exploration of Mars and similar activities are conducted in the future people will remain in space for much longer periods of time, so the issue of renal stone formation needs to be addressed.

The research on prevention measures was conducted jointly by Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA).

They collected data on bone changes for 17 astronauts from different countries who stayed aboard the International Space Station (ISS) for six months between 2009 and 2016, and compared their condition before and after flight. They gave bisphosphonate, a medicine to treat osteoporosis, to seven astronauts once a week prior to their flight and discovered their urine calcium levels was reduced. “The medicine suppressed the loss of bone mass,” explained Okada, a lecturer at the school.

Meanwhile, the calcium level increased for the remaining 10, who experienced bone loss. Other reasons for higher calcium levels can be attributed to weaker blood flow to the kidneys in space, and low amounts of urine due to insufficient water intake.

The study was the first research that established preventive effects for the risk of renal stone formation for long-term stays in space, and its findings were announced in a conference held in the U.S. in September.

Up until now countermeasures mostly involved doing squats and other exercises to build up bone and muscle, but there had been no prevention through medication.

“We explained the effects of taking the medicine, including side effects, and more astronauts are taking it . . . I hope this will contribute to the treatment of kidney stones for the general public as well,” said Okada.

Calcium, oxalic acid, phosphorus and other minerals in the urine may crystallize to form kidney stones. When they move in the urinary tract, they can cause severe pain and blood in the urine. The number of patients suffering from the disease has increased threefold since 1965, from 43 people per 100,000 at that time to 134 in 2005. Stones with a diameter of approximately 0.5 cm can be discharged naturally, but if they grow to be 1 cm or larger, the patient needs to be treated by breaking the stone using shock waves.

This section, appearing Tuesdays, features topics and issues from the Chubu region covered by the Chunichi Shimbun. The original article was published Dec. 10.

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