From the publication:

Data from 18,055 males with known CS status and low TT levels who received TRT at the Veterans Health Administration between December 1, 1999, and May 31, 2014, were grouped into (1) current smokers with normalized TT, (2) current smokers with nonnormalized TT, (3) nonsmokers with normalized TT, and (4) nonsmokers with nonnormalized TT.

[…]

Our findings show that maintaining normal levels of testosterone in testosterone-deficient nonsmokers reduces all-cause mortality and MI [myocardial infarction]. Cigarette smoking negates the beneficial effects of testosterone level normalization after TRT on MI and all-cause mortality. Adequately powered randomized clinical trials would be needed for conclusive determination of the effects of CS [cigarette smoking] and TRT [testosterone replacement therapy ] on CV [cardiovascular] risk and mortality. However, conducting such a randomized clinical trial in the United States would be prohibitive because smoking is an established risk factor for CVD. Based on the present study, counseling and treatment for smoking cessation would be an important intervention before and during TRT. Acknowledging the limitations of a retrospective analysis, results presented in the article provide insight and information that may be valuable in clinical practice.