We thought the answer was YES (some people think the answer is CAN'T TELL).
- The patients, the health workers and the study personnel were blinded.
- Only the person who did the randomisation knew which mattress participants received.
- Participants were unaware that there were two types of mattress.
The trialists checked the participants' subjective perception of the firmness of new mattress (given in table 2). Participants did recognise the degree of firmness of the mattress to some extent. Does it matter? (i.e. if this broke the blinding would the bias thereby account for the results?) We think that if there is a bias from being aware of the firmness of the mattress then it would have tended to favour firm rather than medium mattress because prior belief was that firm ‘orthopaedic’ mattresses were better; we think NO it does not matter.