MAIN RESULTS:

1. Physically active obese persons have reduced risk of atrial fibrillation.

2. Higher fitness is linked to lower risk of atrial fibrillation.
3. Regular exercise and high fitness is associated with lower mortality in persons with atrial fibrillation.

THESIS DEFENCE:

Thesis: Physical activity and cardiorespiratory fitness as determinants of atrial fibrillation incidence and prognosis
Candidate: Lars Elnan Garnvik
Time: March 24, 2020 at 12:15
Place: Online-based solution, due to the covid-19 situation.
Link to university website (in Norwegian)

SUMMARY:

(1) The risk of atrial fibrillation is lowest in the most physically active quartile of the general population. This is especially true in obese persons, according to Garnvik’s first study. Inactive, obese persons had almost twice the risk of atrial fibrillation, compared to the most active, normal weight group. In the most active individuals with obesity, the corresponding risk increase was 50 %.

The study is based on self-reported exercise information from 43,602 men and women who participated in the HUNT3 Study from 2006 to 2008. Almost 1500 of them developed atrial fibrillation before the end of follow-up in 2015.

(2) Men and women are generally at lower risk of atrial fibrillation the higher cardiorespiratory fitness they have. In Garnvik’s study, the fifth of women with the best fitness had only half the risk compared to the least fit women. In men, the lowest risk was observed in the fourth quintile. The results are based on almost 40,000 participants from HUNT3, of which more than 1000 had a confirmed diagnosis of atrial fibrillation within the eight year follow-up period. Their fitness was estimated with a validated Fitness Calculator.

The study also links improved fitness over time to lower atrial fibrillation risk. More than 22,000 of the study participants had also participated in HUNT2 eleven years before HUNT3. Those who improved their estimated fitness over the years had nearly half the risk of developing atrial fibrillation, compared to those who decreased their fitness level between the surveys.

(3) Both regular physical activity and high cardiorespiratory fitness seem to protect against early death and major cardiovascular events in persons with established atrial fibrillation. Those who reported to exercise according to the national exercise recommendations were at half the risk compared to those who were less physically active. Furthermore, every increase of 1 MET in estimated cardiorespiratory fitness was linked to 12 and 15% decreased risk of all-cause and cardiovascular mortality, respectively.

The study includes 1117 patients who had established atrial fibrillation when they participated in the HUNT3 Study. Their mean age was 70, and they were followed until 2015. Exercise at both moderate and high intensity was associated with improved prognosis. As opposed to active persons with atrial fibrillation, inactive persons with this condition had higher mortality risk than inactive persons without atrial fibrillation.

REFERENCES:

(1) Garnvik, L. E., Malmo, V., Janszky, I., Wisløff, U., Loennechen, J. P., & Nes, B. M. (2018). Physical activity modifies the risk of atrial fibrillation in obese individuals: the HUNT3 study. European journal of preventive cardiology, 25(15), 1646-1652.

(2) Garnvik, L. E., Malmo, V., Janszky, I., Wisløff, U., Loennechen, J. P., & Nes, B. M. (2019). Estimated cardiorespiratory fitness and risk of atrial fibrillation: the HUNT study. Med. Sci. Sports Exerc, 51, 2491-7.

(3) Garnvik, L. E., Malmo, V., Janszky, I., Ellekjær, H., Wisløff, U., Loennechen, J. P., & Nes, B. M. (2020). Physical activity, cardiorespiratory fitness, and cardiovascular outcomes in individuals with atrial fibrillation: the HUNT study. European Heart Journal.