Physical activity and atrial fibrillation risk in the middle-aged and elderly

Albrecht et al. investigated, in a report published in this issue of the journal,1 7018 participants aged 55 years and older from the Rotterdam Study with information on non-occupational physical activity between 1997 and 2001. Cox proportional hazards models were used to examine the association of physical activity with atrial fibrillation risk. Models were adjusted for biological and behavioural risk factors and the remaining physical activity types. Physical activity was categorized in tertiles and the low group was used as reference. During 16.8 years of follow-up (median: 12.3 years, interquartile range: 8.7–15.9 years), 800 atrial fibrillation events occurred (11.4% of the study population). A lack of a significant effect remains when analysing each type of physical activity (walking, sports, cycling, gardening and hobbies during the past year as collected by replies to the Zutphen questionnaire) and is independent of sex and age. They thus concluded that no association exists between total physical activity and atrial fibrillation risk in any model. The study is a negative one and it was started without a clear-cut hypothesis. Yet the question explored is relevant and the methods of investigation correct. There are, however, limits to exploring precisely how the assessed types of non-occupational physical activity might interfere, and with whom, as far as atrial fibrillation incidence is concerned. I briefly outline in this comment the most relevant points that should be critically considered.