Abstract: Fifty six trials met the inclusion criteria, involving 3257 children of whom 2412 used an alarm. The quality of many trials was poor, and evidence for many comparisons was inadequate. Most alarms used audio methods. Compared to no treatment, about two thirds of children became dry during alarm use (RR for failure 0.38, 95% CI 0.33 to 0.45). Nearly half who persisted with alarm use remained dry after treatment finished, compared to almost none after no treatment (RR of failure or relapse 45 of 81 (55%) versus 80 of 81 (99%), RR 0.56, 95% CI 0.46 to 0.68). There was insufficient evidence to draw conclusions about different types of alarm, or about how alarms compare to other behavioural interventions. Relapse rates were lower when overlearning was added to alarm treatment (RR 1.92, 95% CI 1.27 to 2.92) or if dry bed training was used as well (RR 2.0, 95% CI 1.25 to 3.20). Penalties for wet beds appeared to be counter-productive. Alarms using electric shocks were unacceptable to children or their parents. Although desmopressin may have a more immediate effect, alarms appeared to be as effective by the end of a course of treatment (RR 0.85, 95% CI 0.53 to 1.37) but their relative effectiveness after stopping treatment was unclear from two small trials which compared them directly. Evidence about the benefit of supplementing alarm treatment with desmopressin was conflicting. Alarms were not significantly better than tricyclics during treatment (RR 0.59, 95% CI 0.32 to 1.09) but the relapse rate was less afterwards (7 of 12 (58%) versus 12 of 12 (100%), RR 0.58, 95% CI 0.36 to 0.94). However, other Cochrane reviews of desmopressin and tricyclics suggest that drug treatment alone, while effective for some children during treatment, is unlikely to be followed by sustained cure as almost all the children relapse. Alarm interventions are an effective treatment for nocturnal bedwetting in children. Alarms appear more effective than desmopressin or tricyclics because around half the children remain dry after alarm treatment stops. Overlearning (giving extra fluids at bedtime after successfully becoming dry using an alarm), dry bed training and avoiding penalties may further reduce the relapse rate. Better quality research comparing alarms with other treatments is needed, including follow-up to determine relapse rates.

Plain-language summary: The review of trials found 56 studies involving 3257 children. Alarm interventions reduce night-time bed wetting in about two thirds of children during treatment, and about half the children remained dry after stopping using the alarm. Alarms take longer to reduce bedwetting than desmopressin, but their effects continue after treatment in half the children who use alarms. So alarms are better in the long term than treatment with desmopressin or tricyclic drugs. Overlearning (giving children extra fluids at bedtime after successfully becoming dry using an alarm) and dry bed training (getting children to go to the toilet repeatedly and changing their own sheets when they wet) may reduce the relapse rate. There are no serious side-effects, which can occur with drug treatment. However, children need more supervision and time from other family members at first. There was not enough evidence with which to compare alarms with other non-drug treatments. Because some of the studies were of poor quality, better research comparing alarms with other treatments is needed, including follow-up to measure relapse rates.