Table 1.

Search strategy (Boolean operators ‘or’ and ‘and’ between columns)

Intellectual disability	Sleep	Adult (>18 years)
intellectual disability, intellectually retarded, intellectually disabled, mental disability, mentally disabled, idiocy, mental deficiency, learning disability, learning disorder, learning disturbance, developmental disability, mental handicap, mentally handicap, intellectual handicap, intellectually handicap, Down syndrome, mental incapacity, intellectual incapacity and oligophrenia	sleep, sleep disorder, insomnia, dyssomnia, parasomnia, parasomnias, somnolence, hypersomnia, circadian, wake, ultradian, night terrors, sleepwalking, somnambulism, nightmares, sleep apnoea, nocturnal, hypnotics, soporific, REM, nap, narcolepsy, snoring and sleep paralysis	adult, middle aged, ageing, elderly, geriatric, old and senior