We have read the research paper entitled ‘Sex-specific time trends in incident atrial fibrillation and the contribution of risk factors: the Tromsø Study 1994–2016’ by Sharashova E. et al.1 Here, we would like to draw your attention to a few points of the study. In the Tromsø Study, it has been indicated that atrial fibrillation (AF) incidence decreased in women and increased following a reverse U-shape in men between 1994 and 2016. Reduction in blood pressure had the largest contribution to the decrease in AF incidence in women, and increase in body mass index (BMI) had the largest contribution to the increase in AF incidence in men. Body mass index increase in women had almost no effect on the AF incidence trend. On the other hand, increase in BMI in men doubled AF incidence rate and obesity is recognized as an independent risk factor for the incidence and progression of AF. The study named ‘Obesity and the risk of new-onset atrial fibrillation’ revealed that in multivariable models adjusted for cardiovascular risk factors, a 4% increase in AF risk per 1-unit increase in BMI was observed both in men and in women.2 In the study, the maximum difference between the mean BMI in males was 1.2 kg/m2. So, it is doubtful to explain the two-fold increase in AF incidence in males by associating it with increase in BMI alone. The Women’s Health Study, which included 34 309 women, revealed that for each 1 kg/m2 increase in BMI, there is a 4.7% increase in the risk of developing AF.3 However, in the Tromsø Study, BMI increase in women had almost no effect on the AF incidence trend. The fact that the increase in BMI led to different results between male and female groups suggests that other factors may be effective.
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