Five comparator analyses were conducted including: (a) sildenafil vs. matched non- sildenafil, (b) sildenafil vs. diltiazem (an anti-hypertensive drug), (c) sildenafil vs. losartan (an anti-hypertensive drug candidate in an AD clinical trial [ClinicalTrials.gov Identifier: NCT02913664]), (d) sildenafil vs. glimepiride (an anti-diabetic drug), and (e) sildenafil vs. metformin (an anti-diabetic drug in an AD clinical trial [ClinicalTrials.gov Identifier: NCT00620191]). For each comparator, we estimated the propensity score by using the variables described in Table 1. Then, we estimated the un-stratified Kaplan-Meier curves, conducted propensity score stratified (n strata = 10) log-rank test and Cox model.