Melatonin improves abdominal pain in irritable bowel syndrome patients who have sleep disturbances: a randomised, double blind, placebo controlled study

Abstract

Background and aims: Melatonin, a sleep promoting agent, is involved in the regulation of gastrointestinal motility and sensation. We aimed to determine if melatonin was effective in improving bowel symptoms and sleep disturbances in irritable bowel syndrome (IBS) patients with sleep disturbance.

Methods: Forty IBS patients (aged 20-64 years; 24 female) with sleep disturbances were randomly assigned to receive either melatonin 3 mg (n = 20) or matching placebo (n = 20) at bedtime for two weeks. Immediately before and after the treatment, subjects completed bowel, sleep, and psychological questionnaires, and underwent rectal manometry and overnight polysomnography.

Results: Compared with placebo, melatonin taken for two weeks significantly decreased mean abdominal pain score (2.35 v 0.70; p<0.001) and increased mean rectal pain threshold (8.9 v -1.2 mm Hg; p<0.01). Bloating, stool type, stool frequency, and anxiety and depression scores did not significantly differ after treatment in both groups. Data from sleep questionnaires and polysomnography showed that the two week course of melatonin did not influence sleep parameters, including total sleep time, sleep latency, sleep efficiency, sleep onset latency, arousals, duration of stages 1-4, rapid eye movement (REM) sleep, and REM onset latency.

Conclusions: Administration of melatonin 3 mg at bedtime for two weeks significantly attenuated abdominal pain and reduced rectal pain sensitivity without improvements in sleep disturbance or psychological distress. The findings suggest that the beneficial effects of melatonin on abdominal pain in IBS patients with sleep disturbances are independent of its action on sleep disturbances or psychological profiles.

Figure 1

Anorectal sensory pressure thresholds of irritable bowel syndrome patients before and after two weeks of treatment. Each bar represents mean (SEM) (n = 20). *p = 0.007 compared with urgency before melatonin treatment (paired t test); *p = 0.004 compared with urgency after placebo treatment (independent t test). **p = 0.003 compared with pain before melatonin treatment (paired t test); **p = 0.007 compared with pain after placebo treatment (independent t test).

Figure 2

Anorectal sensory volume thresholds of irritable bowel syndrome patients before and after two weeks of treatment. Each bar represents mean (SEM) (n = 20). *p = 0.011 compared with urgency before melatonin treatment (paired t test); *p = 0.01 compared with urgency after placebo treatment (independent t test). **p = 0.014 compared with pain before melatonin treatment (paired t test); **p = 0.02 compared with pain after placebo treatment (independent t test).

Figure 3

Anorectal manometry of irritable bowel syndrome patients before and after two weeks of treatment. Each bar represents mean (SEM) (n = 20). There were no significant differences in resting, pushing, or squeezing pressures before or after melatonin treatment.