Summary of Study Methods and Participation By Recruitment Phase of the UK COSMOS Study, 2009–2012.

Footnotes: a Total includes N = 53 additional volunteers who were recruited between Phase 3 and 5 (and chronologically collectively classed as Phase 4), in response to various recruitment strategies, including 2 participants recruited via a Facebook advert trial; these strategies were run concurrently and response rates cannot be calculated for comparisons, therefore are not shown in detail here. b Gift voucher offer in Phase 6 ceased at Day 25 (17/06/2012). c Gift voucher offer in Phase 7 ceased at Day 20 (05/09/2012), as recruitment target of 100,000 reached. d Number of invitations actually received, opened and read may be lower, e.g. if invitation is returned to Sender Summary of Study Methods and Participation By Recruitment Phase of the UK COSMOS Study, 2009–2012.