Objective: Atrial fibrillation (AF) is very frequent and clinically significant arrhythmia. The incidence of atrial fibrillation is continuously rising. Meanwhile several risk factors for AF development have been identified but the etiology is not cleared. Methods: A systematic review and re-analysis of studies which investigated the relationship between AF and some risk factors was conducted. The method of the conditio sine qua non relationship, the method of the conditio per quam relationship, the method of the exclusion relationship and the mathematical formula of the causal relationship k were used to proof the hypothesis. Significance was indicated by a p-value of less than 0.05. Results: The studies analyzed were able to provide direct and indirect evidence that AF is caused by a process of inflammation while a direct identification of the factor causing AF was not possible. Still, it appears to be very probable that Epstein-Barr virus (EBV) is the cause of AF. Conclusion: Atrial fibrillation (AF) appears to be caused by an EBV inflammatory process.

Objective: This study presents a systematic meta-analysis of the relationship between Helicobacter pylori (HP) infection and gastric cancer (GC). Materials and Methods: Twelve articles including 21589 subjects were selected (1237 cases and 20352 controls). These data were analyzed using the mathematical formula of the conditio sine qua non relationship and the causal relationship formula. Results: The data re-analyzed support the Null hypothesis without a Helicobacter pylori infection no human gastric cancer. The causal relationship between HP and GC is highly significant. Conclusion: Helicobacter pylori is the cause of human gastric cancer.

Objective: The aim of this study is to re-evaluate the relationship between smoking and lung cancer. Methods: In order to clarify the relationship between cigarette smoking and lung cancer, a review and meta-analysis of appropriate studies with a total sample size of n = 48393 was conducted. The p-value was set to p < 0,05. Results: It was not possible to reject the null-hypothesis H₀: without smoking no lung cancer. Furthermore, the null-hypothesis H₀: No causal relationship between smoking and lung cancer was rejected. Conclusions: Compared to the results from previous studies, the results of this study confirm previously published results. According the results of this study, without smoking no lung cancer. Smoking is the cause of lung cancer. Keywords: Smoking, lung cancer, causal relationship