Dietary Salt Reduction Tied To Improvement With Overactive Bladder

Some patients with overactive bladder who reduce dietary salt intake may experience improvements in urinary symptoms, a small study suggests.

Researchers examined data on 98 patients diagnosed with overactive bladder who received a brochure advising salt reduction as well as health education every four weeks for 12 weeks. Overall, 71 patients (72.4%) effectively reduced their salt intake, while the remaining 27 patients (27.6%) did not.

Among those who did accomplish the reduction, mean estimated daily salt intake declined from 10.4 grams at baseline to 7.7 grams at 12 weeks. Over the same period, mean daytime frequency of urination dropped from 8.4 to 6.8 times, and mean nighttime frequency declined from 2.5 to 1.6 times.

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In addition, 17 patients who reduced salt intake improved so much they no longer met the diagnostic criteria for overactive bladder by the end of the study, the authors note in Scientific Reports.

"I think that improved eating habits such as reducing salt may be useful not only for treatment but also for prevention of overactive bladder syndrome," said study co-author Dr. Yasuyoshi Miyata of the department of urology at Nagasaki University Graduate School of Biomedical Sciences in Japan.

"In addition, there are no adverse events or financial burdens," Dr. Miyata said by email. "Salt reduction should be recommended treatment for patients with overactive bladder."

The minority of patients in the study who didn't succeed in reducing their dietary salt intake had worse overactive bladder symptoms by the end of the study than they did at baseline.

Among these patients, mean estimated daily salt intake rose from 9.6 grams at baseline to 11.5 grams at 12 weeks. And over this time, mean daytime frequency of urination increased from 8.4 to 9 times, and mean nighttime frequency climbed from 2.3 to 2.6 times.

Beyond its small size, another limitation of the study is the lack of a placebo control group, the study team notes.

Researchers also lacked data on how salt reduction might influence outcomes such as blood pressure, body mass index (BMI), oxidative stress, and neurotransmitters. Changes in any of these factors might also influence the course of overactive bladder syndrome, the authors point out.

Patients in the group that didn't restrict salt also tended to have a higher BMI than those who did achieve this study goal, said Dr. Benoit Peyronnet, a urologist at the University of Rennes in France who wasn't involved in the study. This is one drawback of the study not being randomized, Dr. Beyronnet said by email.

The patients in the salt reduction group were thinner, and therefore more likely to apply all dietary modifications such as no alcohol or less sugar, which may have biased the results, Dr. Peyronnet said.

"The take-home message for clinicians is that among other lifestyle modifications, encouraging overactive bladder patients to decrease their salt intake may reduce their overactive bladder symptoms - especially nocturia," Dr. Peyronnet said. "We did not know that until recently."

—Lisa Rapaport

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