Atrial fibrillation is extremely rare in people younger than 40, occurring in about 0.5 percent of people in that age group.
One study has shown that over 50 percent of young people with atrial fibrillation have an unknown abnormal structure to their heart. More than 25 percent of the participants also had other abnormal heart rhythms, the most common being supraventricular tachycardia. Experts wonder if there may be a connection in young people between these two abnormal rhythms.
Atrial fibrillation can also be a rare complication of pregnancy. It’s believed the heart and lung changes that occur during pregnancy, even in healthy women, increase the risk of AFib. Unlike the previous study, 94 percent of women in this group had a structurally normal heart.