A matched no LBP control group was identified from those without LBP, using a propensity score matching approach (as described above). Each respondent with LBP was paired with a suitable no LBP respondent, based on their demographic and health history characteristics. One LBP respondent had a sufficiently extreme pattern of demographic and health history characteristics that no suitable control was found. Therefore, the remaining analyses focused on the N=1,897 respondents who reported LBP, and the matched no LBP control group of N=1,897 (Table 2).