Currently, β3-adrenergic receptor agonists are used to treat an increasing number of patients with overactive bladder (OAB) worldwide; however, there are some problems with ineffectiveness and side effects (1). Nociceptive thresholds are increased after low reactive-level laser therapy (LLLT) and may inhibit nerve fibers (Aδ and C fibers) that transmit signals related to bladder sensation (2,3). Therefore, we hypothesized that LLLT is a novel treatment for OAB and investigated the safety and usefulness of percutaneous LLLT on the lumbar and sacral spinal nerve roots in patients with OAB.

In a parallel-group, randomized, single-blind, sham-irradiated controlled, exploratory study, patients with OAB aged 20 years or older who provided written informed consent were randomly assigned 1:1 to a laser-irradiation group or control group. Patients in the laser-irradiation group were irradiated for 5 min twice a week on both sides of the third sacral foramen for 6 weeks, while patients in the control group were similarly irradiated with a sham laser twice a week for 6 weeks.

The changes in urinary frequency (after 7 weeks to 1 week), the primary endpoint, was 0.3 ± 2.6 in the control group and –0.3 ± 4.2 in the laser-irradiation group, showing no significant difference. However, the secondary endpoints of the change in volume at maximum desire to void without auditory stimulation (–45.3 ± 45.3 vs. 215.6 ± 201.0 mL), vesical capacity at the time of appearance of detrusor overactivity bladder capacity (–4.0 ± 34.6 vs. 74.5 ± 76.4 mL), intravesical pressure at Qmax (3.8 ± 14.6 vs. –28.2 ± 59.6 cmH2O), Abrams-Griffiths number (–5.7 ± 9.7 vs. –40.2 ± 34.4), Overactive Bladder Symptom Score (change in total score, frequency of urination in the daytime, urinary urgency), and International Prostate Symptom Score (change in total score, urination within 2 hours, urinary urgency) showed significant improvements in the laser-irradiation group. These improvements were observed relatively early after the start of irradiation and persisted for at least 6 weeks after the end of irradiation.
Regarding safety, no adverse events were observed in any patient in the laser-irradiation group. There were also no significant changes in blood pressure and pulse rate, and worsening of urinary symptoms or function was not observed.

LLLT was thought to act on the peripheral nerves of the nervous system that control the lower urinary tract function and correct abnormal sensory nerve functions, such as those associated with the Aδ and C fibers. In addition, this function-modifying effect persisted for some time after repeated irradiation, suggesting that long-lasting effects can be expected.

Percutaneous LLLT may safely improve urine storage disorders without exacerbating urinary tract function and could be an effective novel neuromodulation therapy for OAB.

Continence 7S1 (2023) 100951
DOI: 10.1016/j.cont.2023.100951