Modifiable risk factors for atrial fibrillation: targeting preventive strategies

This editorial refers to ‘Sex-specific time trends in incident atrial fibrillation and the contribution of risk factors: the Tromsø Study 1994–2016’, by E. Sharashova et al. https://doi.org/10.1093/eurjpc/zwac234. Atrial fibrillation is an epidemic disease of the Western society that affects millions of individuals worldwide and is associated with impaired quality of life and risks of heart failure, thromboembolism, and death. Data over the past couple of decades have suggested a bothersome increase in both the prevalence and the incidence of atrial fibrillation, paralleled by increasingly unhealthy risk factors, in many countries.1 One of the main questions for preventive cardiologists and policy holders is, therefore, how to effectively stop such adverse trends and reduce the risk of atrial fibrillation and its complications, moving forward. Demographic factors such as advanced age and female sex are associated with increased atrial fibrillation risk, but the absolute incidence rates appear to be higher in men than in women, possibly suggesting a differential impact of other risk factors in women and men.2 In this context, hypertension, obesity, obstructive sleep apnoea, physical inactivity, and high alcohol use are modifiable key risk factors for atrial fibrillation onset,3 and control of these risk factors has shown promising results on the reduction of the burden of atrial fibrillation in patients with established disease.4 In this issue of European Journal of Preventive Cardiology, Sharashova et al.5 sheds important light on the sex-specific trends in the incidence of atrial fibrillation in an interesting study of a Norwegian population–based sample between 1994 and 2016. Furthermore, the authors quantify the relative contribution of modifiable risk factors to the change in incidence of atrial fibrillation in men and women. In brief, the study showed a small but steady decline in age-adjusted incidence rate of atrial fibrillation in women, whereas the rates increased in men from 1994 to 2006 to thereafter decrease again. Interestingly, over time, the age-adjusted average blood pressures appeared to be better controlled for women than for men, and tighter blood pressure control had the greatest impact on the decrease in the incidence of atrial fibrillation in women. For men, an increase in body mass index (BMI) appeared to have the greatest influence on the rising incidence rates observed for the first time period. More men than women were also noted to have untreated or poorly regulated hypertension, which has been reported in other studies as well, and may contribute to a relatively low decline in rates among men and women.6 Notably, a smaller fraction of the variation in incidence rates (collectively around 10%) could be attributed to changes in the measured risk factors among women, while nearly 50% of the changes could be explained in men. Estimations of population-attributable risks are always associated with some insecurity, but even when taking this into consideration, it is notable that adverse trends in BMI alone could explain more than 40% of the changes in atrial fibrillation rates in men in the present study. Since the measured risk factors have previously been associated with rather larger population-attributable fractions, why did changes in each of these risk factor levels not necessarily explain a correspondingly high proportion of the trends in atrial fibrillation?7 And, does it mean we cannot effectively reduce atrial fibrillation burden with an improvement in the reduction of these risk factors? It is likely that a shift in risk factor profiles takes some time to monitor the consequences of in terms of actual disease onset (incidence rates). However, the rather larger population-attributable fractions associated with changes in BMI could imply that weight loss may be an exception and has more immediate effects on atrial fibrillation risks than, for example, on changes in physical activity levels or blood pressure. When comparing the study with previous data, one should also bear in mind that the study cohort is relatively young compared with many other study cohorts. The mean age during the study period ranged from 45 to 59 years. This could influence the results in still unknown directions, given that the aetiology of atrial fibrillation is multifactorial and includes both genetic components and multiple modifiable risk factors. It is possible that genetic variants could impact the role of modifiable risk factors on the development of atrial fibrillation differently compared with an older cohort.8 Further, high-performance and endurance sports, which in the present study increased throughout the study period, is more common among younger individuals and may influence atrial fibrillation risks differently than more moderate levels of exercise.9 Furthermore, the relationship between body size, physical activity, and atrial fibrillation appears to be complex, and previous literature has also suggested that high aerobic fitness levels increased the risk of atrial fibrillation in tall men, but were protective in shorter men, suggesting that more complex statistical modelling in larger samples may be useful to further understand the atrial fibrillation trends in the community.10 A limitation to bear in mind when interpreting the results of the present study was that the participation rate of the surveys unfortunately dropped significantly during the study period, and half of the study population attended two surveys and <20% participated in all three surveys. This could slightly limit the robustness of the proposed explanatory risk factors. Nevertheless, this study adds important insights from Europe regarding the complex relationship between modifiable risk factors and the sex-specific incidence of atrial fibrillation. Furthermore, the study underlines the differences between the sexes in the prevalence and impact of risk factors on the incidence of atrial fibrillation. There is no doubt that obesity, hypertension, sedentary lifestyle, and other risk factors in patients should be treated to prevent not just atrial fibrillation but also other cardiovascular diseases. Management of modifiable risk factors is already an important target in many cardiology outpatient clinics managing patients with atrial fibrillation. This study underscores that more attention should be paid to the sex-specific prevalence in risk factors and continuous control of risk factors in society to improve the reduction rates of the burden of atrial fibrillation. Barriers for the implementation of preventive measures warrant further focus, such as understanding why a relatively large number of individuals (especially men) still have poorly or uncontrolled hypertension. The sex-specific differences in risk factors and how they influence the development of atrial fibrillation are important, and much is still unknown with regard to the physiological explanations to these differences. Further investigation on these sex-specific differences, preferably through large-scale clinical cohort studies, is warranted.