Fig. 1

Organisation chart of participation in the study [18]. Of the 1501 people invited to take part, 448 (32%) replied to the request (100 letters were not delivered) with 239 accepting (53.3%) and 209 declining (46.7%). Of the 239 questionnaires sent to those who accepted to take part, 211 (88.3%) were returned. Of the latter, 27 were then excluded because they did not fulfil the inclusion criteria, leaving therefore 184 questionnaires to be analysed