Data are reported from five validation studies (total n=30 941; 71% female) in which SCI items were administered. The Great British Sleep Survey (GBSS) was an open access, web-based survey completed by adults (18+years) with a UK postcode yielding data on 12 628 participants (72% female; mean age=38.7 years (SD=14.5)) between February 2010 and August 2011.32 The GBSS+ was a revision of the GBSS, extended to any valid zip code worldwide, from May 2011 to March 2012 (n=11 017; 68% female; 42.3 years (16.5)). The TV sample was obtained in response to a network programme (the Food Hospital, Channel 4) on the sleep benefits of tart cherry juice (n=6876; 76% female, 36.4 years (13.3)). Glasgow Science Centre data (n=256; 56% female, 40.3 years (14.9)) were collected in 2009–2010 during a study which assessed the relationship between salivary α-amylase, sleep pressure and diurnal preference.33 (link) Finally, a randomised controlled trial (RCT) sample comprised 164 participants (72% female, 48.9 years (13.7)) recruited into a placebo-controlled evaluation of CBT for insomnia.34 (link) Ethical agreement concerning the latter two studies is provided in the source manuscripts. For the open access web surveys, participation was covered by the site terms.
Across our combined largest samples (GBSS, GBSS+, TV), women were slightly younger than men (38.5 (14.9) vs 40.1 (14.7) years; t(27 638)=7.94, p<0.0001) and the great majority was in average or better physical health (86%) and mental health (82%; 5-point scale: 0 ‘very good’, 1 ‘good’, 2 ‘average’, 3 ‘poor’ and 4 ‘very poor’). Respondents who made some use of prescription sleeping pills (9.1%) were 7 years older than those who did not (46.2 (15.1) vs 39.1 (15.1) year, t(20 813)=19.6, p<.0001) and had a substantially poorer SCI score (8.56 (4.93) vs 15.6 (7.80), t(20 813)=38.8, p<0.0001). Of the total sample, 18.1% took over-the-counter sleep aids (OTCs), and more than one-third of those taking sleeping pills also used OTCs.