Supine Hypertension as a Predictor of Atrial Fibrillation: A UK Biobank Cohort Study

Atrial fibrillation (AF) is a common arrhythmia strongly associated with blood pressure (BP), yet most current assessments focus only on seated BP measurements. Supine BP may offer additional predictive value by capturing positional or autonomic variations often missed in standard evaluations.

This study aimed to investigate the association between supine BP and incident AF.

We analyzed 24,901 UK Biobank participants without prior cardiovascular disease or antihypertensive treatment, categorizing them into 4 groups based on the presence of seated and/or supine hypertension: normal BP, seated-only hypertension, supine-only hypertension, and both seated and supine hypertension. The primary endpoint was incident AF over a median follow-up of 4.5 years.

Among 24,901 participants (mean age 63.1 ± 7.7 years; 44.0% male), supine systolic BP was independently associated with incident AF (adjusted HR [aHR]: 1.12 per 10 mm Hg increase; 95% CI: 1.05-1.20), whereas seated systolic BP showed a weaker association. Supine hypertension (aHR: 1.38; 95% CI: 1.09-1.75) and both seated and supine hypertension (aHR: 1.35; 95% CI: 1.01-1.81) significantly increased AF risk, whereas seated hypertension alone did not. Supine hypertension improved AF risk prediction, increasing Harrell C-index (0.553 vs 0.576; P = 0.033) and net reclassification improvement (22.3%; P < 0.001). In participants <65 years, supine hypertension showed the strongest association with AF, but no significant association was observed in older adults.

Supine hypertension is independently associated with increased AF risk, especially in younger adults. Seated hypertension was not independently associated with AF risk after adjustment. These findings suggest that supine BP may capture prognostic information beyond seated BP measurements.