Characteristics of included abstracts
| Characteristic | Category | N (%) |
| Year | 2016 | 53 (30.1) |
| 2017 | 64 (36.4) | |
| 2018 | 59 (33.5) | |
| No of authors | <4 | 21 (11.9) |
| 4–7 | 88 (50.0) | |
| >7 | 67 (38.1) | |
| Continent | North America | 135 (76.7) |
| Europe | 15 (8.5) | |
| Oceania | 15 (8.5) | |
| Asia | 8 (4.6) | |
| South America | 3 (1.7) | |
| Type of intervention | Pharmacological | 44 (25.0) |
| Non-pharmacological | 132 (75.0) | |
| No of centres | Single centre | 160 (90.9) |
| Multicentre | 16 (9.1) | |
| Word count | <250 | 3 (1.7) |
| 251–300 | 17 (9.7) | |
| 301–350 | 125 (71.0) | |
| >350 | 31 (17.6) | |
| Research area | Insomnia | 96 (54.5) |
| Sleep-related breathing disorders | 48 (27.3) | |
| Others | 32 (18.2) | |
| Sample size | <25 | 46 (26.1) |
| 25–100 | 63 (35.8) | |
| >100 | 67 (38.1) | |
| Funded by industry | Yes | 46 (26.1) |
| No | 130 (73.9) | |
| Overall | 176 (100) |