# Table 2 Methodologies' modifications taking into account prevalence-based analysis in cohort studies as base method

Peto's et al method Prevalence-based analysis in case-control studies Basic method
Variation respect prevalence-based analysis in cohort studies Problem: Smoking prevalence is a poor proxy for cumulative hazards of smoking.
Solution: Defining SIR (Smoking impact ratio or Synthetic prevalence) authors avoid prevalence limitations.
Problem: RR extrapolation to different populations than the original is inconsistent.
Solution: Designing a case-control study OR could be assessed.
Problem: RR extrapolation to different populations than the original is inconsistent.
Solution: RR can be estimated applying a calculation procedure.
Calculation procedure $SIR=\frac{{C}_{LC}-{N}_{LC}}{{S}_{LC}^{*}-{N}_{LC}^{*}}$
where CLC, NLC, S*LC, N*LC are age-sex specific lung cancer mortality rates for smokers and never smokers in the study and in the reference population (*).
$OR=\frac{{a}_{1}{b}_{0}}{{a}_{0}{b}_{1}}RR=\frac{{a}_{1}\left(1-{p}_{1}\right)}{{a}_{0}{p}_{1}}$
where
p1 is the prevalence between the cases
a1 is exposed cases
b1 is exposed controls
a0 is non exposed cases
b0 is non exposed controls
Packs-function in smokers
RRs = 1 + ac((t - 5))-t0)
Multistage-function in smokers
RRs = 1 + [(t - 5)4.5 + ac(1 + 2ac)((t - 5)-t0)4.5 + 2ac((t - 5)4.5-t0 4.5)]/(t - 5)4.5
Where a is a constant, c is the number of packs of cigarettes smoked per year, t is the current age and t 0 is age at start of smoking.
In former smokers t1 replaces (t - 5) and t1 is age at stop smoking. 