Sleep Restriction Therapy comprised one 40-minute individual face-to-face session using Spielman et al., (1987) initial instructions [20]. In line with previous guidance, a minimum time in bed (TIB: sleep window) was set at 5 hours [16, 21]. The sleep window was anchored with a morning wake-up
time to suit individual patient daytime commitments. The therapist then calculated the initial
go to bed ‘threshold time’. Patients were instructed to not go to bed until after the threshold
time and to only go to bed if they felt ‘sleepy tired’. The intervention was standardised and sup-
ported by a brief set of digital slides (8 in total) and an information manual (11 pages, in plain
English