The problem – called nocturia – which mainly affects the over-60s, leads to disrupted sleep and can significantly affect people’s lives.
In a study of more than 300 volunteers, researchers found that reduced salt intake led people to urinate less.
Advice to follow a sensible diet could help improve symptoms, UK doctors said.
The researchers, from Nagasaki University, presented their findings at the European Society of Urology congress in London.
They followed patients who had a high salt intake and sleeping problems for three months, after giving them advice to cut back on salt in their diet.
On average, trips to the loo fell from more than twice a night to just one.
This happened at night as well as during the day, and their quality of life also improved.
Feeling the urge
Conversely, 98 people in the study ended up eating more salt than normal and found they went to the loo more often at night-time.
Study author Dr Matsuo Tomohiro said larger studies were needed to confirm the link but the results could offer help for older people.
“This work holds out the possibility that a simply dietary modification might significantly improve the quality of life for many people,” he said.
Prof Marcus Drake, a nocturia expert from the University of Bristol, said the amount of salt people ate was not generally considered to be a cause of nocturia.
Usually, doctors tended to focus on the volume of water patients drank before bedtime and on bladder and prostate problems (in men), he said.
“Here we have a useful study showing how we need to consider all influences to get the best chance of improving the symptom.”
The need to wake up at night to empty the bladder affects more than half of men and women over the age of 50.
It is particularly common in elderly people, many of whom get up at least twice a night.
When you start to need to make two or more trips to the bathroom at night, sleep is being disturbed – which can lead to stress, tiredness and irritability.
