At least 10.55 million American adults have atrial fibrillation (AFib), making it the most common heart rhythm disorder in the country. That figure, based on data through the end of 2019, represents about 4.5% of the adult population. The true number is likely higher today, given population aging and improved detection.
What the Numbers Actually Look Like
The 10.55 million estimate comes from a 2024 analysis published in the Journal of the American College of Cardiology, which called the trend an “alarming surge.” That 4.48% prevalence rate means roughly 1 in 22 American adults has AFib. To put that in perspective, it’s more common than diabetes among adults over 65.
These numbers have climbed steadily for decades, driven largely by an aging population and better screening. AFib prevalence rises sharply with age. Among adults 65 and older, about 10% have the condition. Among working-age adults, the rate drops below 1%.
Many Cases Go Undetected
Not everyone with AFib knows they have it. Research estimates that roughly 700,000 Americans are living with undiagnosed AFib, accounting for about 13% of all cases. Among older adults, nearly 14% of those with AFib haven’t been diagnosed. Among working-age adults, about 11% of cases are undiagnosed.
This matters because AFib often produces no obvious symptoms. Some people feel heart palpitations, shortness of breath, or fatigue. Others feel nothing at all. The condition can come and go in episodes lasting minutes or hours, making it easy to miss during a routine doctor’s visit. And undiagnosed AFib still carries serious risks: more than half of people with undetected AFib already have risk factors that would qualify them for treatment to prevent stroke.
Who Gets AFib
Age is the single biggest risk factor. AFib is uncommon before 50 and increasingly common with each passing decade. By 85, it affects a substantial share of the population.
Race and ethnicity also play a role, though the pattern may surprise you. White Americans have the highest reported incidence of AFib. Compared to white adults, Hispanic Americans have about 51% lower incidence, Black Americans about 37% lower, and Chinese Americans about 40% lower, according to data from the Multi-Ethnic Study of Atherosclerosis. Researchers have debated whether this reflects true biological differences or gaps in diagnosis and healthcare access. The disparity is consistent enough across studies that some real difference in susceptibility likely exists, but underdiagnosis in minority communities also plays a part.
Men develop AFib at slightly higher rates than women overall, though women make up a large share of total cases because they tend to live longer.
Why AFib Is More Than a Nuisance
AFib increases your risk of stroke roughly fivefold. The irregular heartbeat allows blood to pool in the heart’s upper chambers, where it can form clots. If a clot travels to the brain, the result is a stroke. AFib is responsible for at least 15% of all strokes in the United States.
Strokes caused by AFib tend to be more severe than other types. They’re more likely to cause lasting disability or death. This is why diagnosis matters so much, even for people who feel fine. Blood-thinning medications can dramatically reduce stroke risk in people with AFib, but only if the condition has been identified.
Beyond stroke, AFib is linked to heart failure, cognitive decline over time, and reduced quality of life. The heart works less efficiently when it beats irregularly, and over months or years, that takes a toll.
The Financial Burden
AFib is expensive to manage. Americans with the condition spend an average of $25,451 per year on healthcare, compared to about $9,254 for those without it. After adjusting for other health differences, AFib adds roughly $6,185 in annual costs per person. The biggest expenses are hospital stays and prescription medications. Total AFib-related healthcare spending in the U.S. increased by 11.1% between 2016 and 2021, and that trend shows no sign of reversing.
Wearable Devices Are Changing Detection
Smartwatches and fitness trackers are now capable of flagging possible AFib, which could help close the gap in undiagnosed cases. The Fitbit Heart Study, one of the largest real-world tests of wearable AFib detection, found that the device’s algorithm had a specificity of 98.4%, meaning it rarely flagged someone who didn’t have AFib. Sensitivity was lower at 67.6%, meaning it caught about two-thirds of AFib episodes during monitoring.
That trade-off is intentional. Wearable manufacturers calibrate their algorithms to minimize false alarms. A notification from your watch isn’t a diagnosis, but it’s a reasonable signal to follow up with a doctor for a proper electrocardiogram. For the estimated 700,000 Americans walking around with undetected AFib, a wrist-based alert could be the first step toward treatment that prevents a stroke.
The Numbers Will Keep Growing
AFib prevalence is projected to rise substantially over the coming decades. Among women alone, the American Heart Association projects prevalence will climb from 1.58% to 2.31% between 2020 and 2050. When you factor in men (who have higher rates) and the overall aging of the U.S. population, total cases could reach well beyond 12 to 16 million by mid-century. The baby boomer generation entering their 70s and 80s over the next decade will accelerate this trend considerably. More AFib means more strokes, more heart failure, and higher healthcare costs unless screening and treatment keep pace.