Figure 2.

A-B, Estimated incident rate ratios (95% CI) for the association between pneumonia and log10 (parts per million) (A) and pneumonia and carboxyhemoglobin exposure exposure fit as a categoric variable in quintiles (B). The lowest quintile (lowest 20% of exposure values) is the reference level for other estimates. Models are adjusted for age, presence of smokers in the household, sex, randomization arm, visit number, and follow-up time, and are clustered on an individual period. CO = carbon monoxide; COHb = carboxyhemoglobin; IRR = incident rate ratio.