ObjectiveData on the contribution of ambulatory blood pressure (ABP) components to the risk of developing atrial fibrillation (AF) are limited. We prospectively tested the hypothesis that ABP may represent a potentially modifiable risk factor for the development of AF in a European population study.MethodsWe recorded daytime blood pressure (BP) in 3956 subjects randomly recruited from the general population in five European countries. Of these participants, 2776 (70.2%) underwent complete 24-hour ABP monitoring. Median follow-up was 14 years. We defined daytime systolic BP load as the percentage BP readings above 135 mm Hg. The incidence of AF was assessed from ECGs obtained at baseline and follow-up and from records held by general practitioners and/or hospitals.ResultsOverall, during 58 810 person-years of follow-up, 143 participants experienced new-onset AF. In adjusted Cox models, each SD increase in baseline 24 hours, daytime and night-time systolic BP was associated with a 27% (P=0.0056), 22% (P=0.023) and 20% (P=0.029) increase in the risk for incident AF, respectively. Conventional systolic BP was borderline associated with the risk of AF (18%; P=0.06). As compared with the average population risk, participants in the lower quartile of daytime systolic BP load (<3%) had a 51% (P=0.0038) lower hazard for incident AF, whereas in the upper quartile (>38%), the risk was 46% higher (P=0.0094).ConclusionsSystolic ABP is a significant predictor of incident AF in a population-based cohort. We also observed that participants with a daytime systolic BP load >38% had significantly increased risk of incident AF.