Associations between physical activity, left atrial size and incident atrial fibrillation: the Tromsø Study 1994-2016.
Level 3 - non-randomized controlled study
Prospective cohort study with long-term follow-up
PubMed 35074937 · doi:10.1136/openhrt-2021-001823
What was done
In the population-based Tromsø Study, 2,479 participants (52.4% female) free from known cardiac pathology were followed prospectively for a median of 20.2 years (1994–1995 through 2016). Baseline left atrial (LA) size was evaluated via anteroposterior LA diameter on echocardiography, and physical activity (PA) was self-reported by questionnaire. The outcome was incident hospital-diagnosed atrial fibrillation (AF), confirmed by electrocardiography.
What was found
PA showed a U-shaped relationship with incident AF. Moderately active participants had a 32% lower risk of AF compared with inactive participants (adjusted HR 0.68, 95% CI 0.50 to 0.93). LA enlargement was associated with a 38% increased AF risk compared to normal LA size (adjusted HR 1.38, 95% CI 1.12 to 1.69). However, physical activity attenuated this risk: active participants with LA enlargement had a 45% lower AF risk compared with inactive participants with LA enlargement (adjusted HR 0.55, 95% CI 0.39 to 0.79), with AF risk comparable to active participants with normal LA size. Patterns were consistent across sexes and in participants over and under 65 years.
Why it matters
While elite endurance training can enlarge the left atrium and predispose to arrhythmias, moderate physical activity appears protective and mitigates the clinical AF risk conferred by structural LA enlargement.
Limits
Physical activity was assessed using self-reported questionnaires, which are prone to misclassification and recall bias. LA size was measured using single-plane anteroposterior diameter rather than indexed left atrial volume. Long-term changes in exercise habits or cardiac structure over the 20-year follow-up were not evaluated.
Cited by
- supports The Tromsø study from Norway demonstrated that 3 to 5 hours of moderate-intensity exercise achieves the lowest risk of atrial fibrillation, with risk increasing above that volume.