Figure 1.

Flow chart of the study populations. ^a27 individuals had an unknown address for the postal-based reminder; ^b61 individuals had an unknown address and 173 did not consent to be invited to a follow-up; ^c27 had an unknown address and 229 did not consent to be invited to a follow-up. An additional 55 who gave their consent, but did not fill out the questionnaire at baseline, were invited, of whom 18 participated. They are defined as non-responders at baseline, and are not included in the present analyses.