Table 1.

Questionnaire given to a representative sample of US and UK survey participants matched for age, gender and ethnicity according to national census data

How many first/second-degree family members do you have?a How many of these first/second-degree family members live in the USA [UK]?a At this very moment, do you have a first-degree family member who is in a coma?b Who is the family member in a coma? How old is your family member in coma? What is the gender of your family member? Does your family member live in the USA [UK]? Is your family member admitted to a hospital in the USA [UK]? What is the condition that caused your family member to be in a coma?c For how long has your family member been in a coma? Is your family member currently admitted to an intensive care unit? [If not:] (i) Does your family member require oxygen supplementation? (ii) Does your family member require nutritional support? (iii) Please describe your family member's physical condition with respect to breathing and feeding as well as you can. Do you have another first-degree family member who is in a coma at this moment? [Questions 3a-3i] Do you have a first-degree family member who has been in a coma within the past 12 months? [Questions 3a-3i] Did your family member survive? (i) Did your family member regain functional independence after coma? At this very moment, do you have a second-degree family member who is in a coma? [Questions 3a–3i] Do you have a second-degree family member who has been in a coma within the past 12 months? [Questions 3a–i] [Questions 5b] Do you personally know someone who is not first- or second-degree family (e.g. a friend, a work colleague, a neighbour) who is in a coma or who has been in a coma within the past year? [Questions 3a–3i]d Have you ever been in a coma yourself? What was the condition that brought you into coma? Have you been in a coma more than once? Do you have diabetes (any type)? Do you have a cleft lip? Is a family member of yours taking this survey too?e

^aParticipants were first inquired about first-degree, then second-degree, family members. First-degree family members were defined as spouses, partners, children, parents, brothers and sisters or any humans that survey participants considered equivalent in terms of emotional and social importance; second-degree family member referred to grandparents, grandchildren, cousins, aunts, uncles or anyone else of similar emotional and social importance. Survey participants had to know with confidence if these people have been admitted to hospital within the preceding 12 months.

^bSee Materials and methods for coma definition.

^cOptions included traumatic brain injury, stroke, cardiac arrest, intoxication with illicit drugs, intoxication (any sort), brain infection (any sort), epilepsy, COVID-19 (primary reason for hospital admission), systemic infection other than COVID-19, liver failure, kidney failure, low or high blood sugar, low oxygen levels and/or low blood pressure, medically induced coma (i.e. a systemic illness that requires artificial coma to stabilize body functions), unknown and other.

^dHere, ‘family member’ was replaced with ‘the patient’.

^eThis question was asked to avoid counting coma cases twice.