“…Over two thirds of studies (69%) concerned just four marginalised groups. The largest of these (constituting over a quarter of studies (26%)) focused on ethnic minority groups [8, 32, 33, 39, 43, 46, 56, 59, 61-63, 66, 74, 82, 84, 93, 94], those residing in care homes (18%) [29, 32, 36, 54, 65, 77-79, 81, 85, 86, 88], followed by frail elderly populations (15%) [34, 37, 38, 51-53, 68, 73, 75, 83, 91, 92, 95], and individuals of low socio-economic status (10%) [40,41,60,69,72,87,90].…”