Pair-wise χ2 tests for equality of coefficients permitted a comparison of risk estimates for wave 2 SRO (shown in table 3) between categories of smoking status change. Given the 3-year interval between waves 1 and 2 and the coding requirement that former smoking status is assigned only upon reporting of at least 12 months of abstinence, long-term former smokers (category 2, table 3) would have been abstinent for at least 4 years. Persons who shifted from current smoking in wave 1 to former smoking in wave 2 (category 3, table 3) would have been abstinent for at least 12 months and a maximum of 4 years.
