Physical activity, resting heart rate, and atrial fibrillation: the Tromsø Study.
Level 3 - non-randomized controlled study
Prospective cohort study with 20-year follow-up
PubMed 26966149 · doi:10.1093/eurheartj/ehw059
What was done
A prospective cohort study evaluated 20,484 adults (50.3% men) who participated in the third Tromsø Study survey in Norway (1986–1987). Baseline physical activity was assessed using a validated questionnaire, and resting heart rate (RHR) was measured objectively. Participants were followed through 2010 (mean follow-up 20 years, 409,045 person-years) for incident cases of hospital-diagnosed atrial fibrillation (AF) documented on electrocardiogram.
What was found
During follow-up, 750 participants (70.5% men) were diagnosed with AF. Compared with the low physical activity group, moderately active individuals had a 19% lower risk of AF (adjusted hazard ratio [HR] 0.81, 95% CI 0.68–0.97). Highly active individuals showed similar risk to the low-activity group, and vigorously active individuals had a non-significantly higher risk (adjusted HR 1.37, 95% CI 0.77–2.43). AF risk decreased as RHR increased (adjusted HR 0.92, 95% CI 0.86–0.98 for each 10 bpm increase in RHR), and RHR < 50 bpm was a statistically significant risk factor for AF (P < 0.05).
Why it matters
The study demonstrates a J-shaped relationship between leisure-time physical activity and AF risk, where moderate physical activity reduces risk but higher activity levels attenuate this benefit. It also identifies low resting heart rate as an independent risk marker for AF.
Limits
Physical activity was self-reported via questionnaire only at baseline and not continuously tracked over the 20-year follow-up. The study only captured hospital-diagnosed cases, likely missing asymptomatic, paroxysmal, or outpatient-managed AF. The population was limited to a single Norwegian cohort, and wide confidence intervals in the vigorously active category indicate limited statistical precision for high-intensity activity.
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.