Background: Scant data exist on incidence rates, correlates, and prognosis of electrocardiographic P-wave abnormalities in the general population.

Methods: We recorded ECG and measured conventional cardiovascular risk factors in 5667 Finns who were followed up for incident atrial fibrillation (AF). We obtained repeat ECGs from 3089 individuals I I years later.

Results: The incidence rates of prolonged P-wave duration, abnormal P terminal force (PTF), left P-wave axis deviation, and right P-wave axis deviation were 16.0%, 7.4%, 3.4%, and 2.2%, respectively. Older age and higher BMI were associated with incident prolonged P-wave duration and abnormal PTF (P <= 0.01). Higher blood pressure was associated with incident prolonged P wave duration and right P-wave axis deviation (P <= 0.01). During follow-up, only prolonged P wave duration predicted AF (multivariable-adjusted hazard ratio, 1.38; P = 0.001).

Conclusions: Modifiable risk factors associate with P-wave abnormalities that are common and may represent intermediate steps of atrial cardiomyopathy on a pathway leading to AF.