In a population-based study from Olmstead County, Minnesota, in which the mean participant age was 66.9 13.3 years, PFO was not associated with increased risk of stroke (HR, 1.46; 95% CI, 0.74 2.88), whereas there was an association with In the multiethnic NOMAS, in which the mean age was 68.7 10.0 years, PFO was not associated with increased risk of stroke (HR, 1.64; 95% CI, 0.87 3.09), nor was the coexistence of PFO and ASA Another study examining the characteristics of PFO observed larger PFOs, longer tunnels, and a greater frequency of ASA in patients with stroke than in those without stroke.490 One study of patients with cryptogenic stroke found that the risk of recurrent stroke was 2.3% (95% CI, 0.3 4.3) among patients with PFO alone, 0% in those with ASA alone, 15.2% (95% CI, 1.8 28.6) in patients with both PFO and ASA, and 4.2% (95% CI, 1.8 6.6) in patients with Further analyses from NOMAS with longer follow- up also failed to find evidence for an increased risk of first stroke with PFO (adjusted HR, 1.10; 95% CI, 0.64 1.91) and provided further evidence that PFO is not associated with sub- clinical cerebrovascular disease.492 No study has examined treatments to prevent initial strokes in patients with PFO or ASA. Accordingly, given the uncer- tainties and relatively low risk of initial stroke caused by PFO or ASA and the potential risk of antithrombotic therapy or invasive treatments, no treatment is recommended for the pri- mary prevention of stroke in people with PFO orASA. 