Letters to the Editor RE: “VALIDATION OF A METHOD FOR RECONSTRUCTING HISTORICAL RATES OF SMOKING PREVALENCE”

In their recent paper, Bilal et al. (1) incorrectly assert that no researchers have assessed the validity of historical smok-ing prevalence derived from retrospectively reported data. A large body of literature validates this type of data in general (2–4) and smoking data in particular (5–12). In fact, at least 2 previously published studies applied an improved method (8, 9) with better data. Bilal et al. correct retrospectively derived smoking preva-lence rates for differential mortality rates of smokers and nonsmokers and validate their estimates against contempora-neously reported data. However, they validate prevalence rates in just 5 prior years using paired surveys that differ by, at most, 20 years. The earlier studies validate prevalence rates in 11 (8) and 27 (9) prior years using paired surveys that differ by up to 40 years. More importantly, Bilal et al. correc