Table 3 shows AORs indicating significant risk for SRO among all categories of ever smokers relative to the persistent never smokers. The highest risk was seen for relapsers (former smoker to current smoker) (AOR=3.42, 95% CI 2.85 to 4.11); new smokers (never-smoker to current smoker) showed the next highest risk (AOR=1.82, 95% CI 1.51 to 2.19); and long-term former smokers (during both wave 1 and 2) showed the least elevated, yet still significant, risk (AOR=1.22, 95% CI 1.12 to 1.34). The seventh category consisting of never smokers in wave 1 who reported former smoker status in wave 2 was too small for a valid analysis.
