Study designs of evaluations included in the review
The inclusion criteria were not explicitly defined for the study design. All of the included studies were crossover randomised controlled trials (RCTs).
Specific interventions included in the review
Studies of passive body heating were eligible for inclusion. The included studies compared the heating of bodies using immersion to mid-thorax or neck level in a warm bath (40.2 or 40.3 degrees C for 10 to 30 minutes, 0.5 to 2 hours before bedtime) with either no bath or a lukewarm bath (38 degrees C). The interventions were conducted at home or in a sleep laboratory, and appear to have been conducted over one night only. Cointerventions included the use of foot warmers or electric blankets.
Participants included in the review
Studies of people aged 60 years and older were eligible for inclusion. The participants in the included studies were healthy people with and without insomnia who were recruited through advertisements in newspapers, were free of mental impairment and were not taking any sleeping tablets. The participants were predominantly female (75%).
Outcomes assessed in the review
Studies that assessed the change in body temperature and subjective measures of sleep quality were eligible for inclusion. The included studies measured the rectal temperature before and after the warm bath, 24-hour rectal temperature and skin temperature. Sleep quality was assessed using sleep efficiency, sleep maintenance, wake after sleep onset (WASO) and slow wave sleep. In the included studies, sleep quality was measured using overnight polysomnography, sleep diary, self-reported post-sleep inventory, 24-hour wrist actigraphy and overnight body movement.
How were decisions on the relevance of primary studies made?
The author did not state how the papers were selected for the review, or how many reviewers performed the selection.