The exact cause of atrial fibrillation is unknown, but it becomes more common with age and affects certain groups of people more than others.

Atrial fibrillation is common in people with other heart conditions, such as:

• high blood pressure
• atherosclerosis
• heart valve disease
• congenital heart disease (heart disease at birth)
• cardiomyopathy (wasting of the heart muscle)
• pericarditis (inflammation of the lining surrounding the heart)

It is also associated with other medical conditions:

• hyperthyroidism (overactive thyroid gland)
• pneumonia
• asthma
• chronic obstructive pulmonary disease
• lung cancer
• diabetes
• pulmonary embolism (a blockage in a vessel in your lungs)
• carbon monoxide poisoning

Not everyone with atrial fibrillation falls into one of the above groups. For example, it can affect extremely athletic people.

Some people with atrial fibrillation have no other conditions, and no cause can be found. This is known as lone atrial fibrillation.

Triggers

Certain situations can trigger an episode of atrial fibrillation, including:

• drinking excessive amounts of alcohol, particularly binge drinking
• being overweight
• drinking lots of caffeine, such as tea, coffee or energy drinks
• taking illegal drugs, particularly amphetamines or cocaine
• smoking