Atrial fibrillation and lifestyle factors with focus on physical activity and alcohol consumption

The overall aim of this thesis was to investigate how modifiable lifestyle factors, with a focus on alcohol consumption and physical activity, influence the risk of atrial fibrillation (AF). The thesis is based on data from two prospective cohort studies of Swedish men (Cohort of Swedish Men) and women (Swedish Mammography Cohort). During 1997, 48,850 men who were born between 1918 and 1952 and lived in Västmanland and Örebro counties and 39,227 women who were born between 1914 and 1948 and lived in Västmanland and Uppsala counties completed a questionnaire about lifestyle and other risk factors for chronic diseases. Information was also gathered from Swedish Inpatient Register, Cancer Registry, Death Registry, and Diabetes Register.

In paper I, we examined the association between alcohol consumption and AF risk in a prospective study of Swedish men and women (n= 79,019) and conducted a meta-analysis of prospective studies (n =7). Alcohol consumption was associated with increased risk of AF in the two Swedish cohorts and in the meta-analysis of all studies. Even moderate intake was associated with increased risk of AF.

In paper II, we investigated the association of physical activity, at different ages and of different types, with risk of AF in a large (n = 48,850) general male population. High level of leisure-time exercise (moderate-intensity to high-intensity physical activity) in younger men was associated with an increased risk of AF later in life. On the other hand, walking/bicycling (low-intensity to moderate-intensity) at an older age was associated with a reduced AF risk.

In paper III, we evaluated the association between physical activity, at different ages and of different types, with risk of developing AF in a large (n = 39,227) general female population. Regular physical activity was associated with a reduced risk of AF in women. Moderate amount of daily physical activity was sufficient to have a significant risk reduction in middle-aged and elderly women. High levels of leisure-time exercise (moderate-intensity to high-intensity physical activity) were not a risk factor for AF in women as previously described in men.

In paper IV we investigated the joint association of four modifiable lifestyle factors (alcohol consumption, body mass index, regular exercise and smoking) on incidence of AF in both men and women. The combination of adopting four healthy lifestyle factors was associated with a halving of the risk of AF.

In conclusion alcohol consumption was associated with an increased risk of AF. A high level of intense physical activity may increase the risk of AF in younger men while low-moderate intense physical activity seems to decrease the risk in both men and women. High levels of intense physical activity were not a risk factor for AF in women. Adopting a healthy lifestyle may significantly reduce the risk of AF in both men and women. AF may partly be preventable through modifiable lifestyle behaviors. Our findings underscore the importance of avoidance of an unhealthy lifestyle.

List of scientific papers

I. Larsson SC, Drca N, Wolk A. Alcohol consumption and risk of atrial fibrillation: a prospective study and dose-response meta-analysis. J Am Coll Cardiol. 2014;64:281-9.
https://doi.org/10.1016/j.jacc.2014.03.048

II. Drca N, Wolk A, Jensen-Urstad M, Larsson SC. Atrial fibrillation is associated with different levels of physical activity levels at different ages in men. Heart. 2014;100:1037-42.
https://doi.org/10.1136/heartjnl-2013-305304

III. Drca N, Wolk A, Jensen-Urstad M, Larsson SC. Physical activity is associated with a reduced risk of atrial fibrillation in middle-aged and elderly women. Heart. 2015;101:1627-30.
https://doi.org/10.1136/heartjnl-2014-307145

IV. Larsson SC, Drca N, Jensen-Urstad M, Wolk A. Combined impact of healthy lifestyle factors on risk of atrial fibrillation: Prospective study in men and women. Int J Cardiol. 2016;203:46-9.
https://doi.org/10.1016/j.ijcard.2015.10.106