The article, Obesity, Physical Activity, and Their Interaction in Incident Atrial Fibrillation in Postmenopausal Women is a well-structured survey and well written article on the modifiers and independent risk factors of atrial fibrillation, (AF) in post-menopausal women. The authors commented on AF as the commonest sustained heart rhythm disorder in the United States. It also reports a known study on obesity as an independent risk factor for incident AF. They went on to demonstrate the increasing risk for AF in obese patients. The authors also showed that physical activity modifies the risk of incident AF in obese patients causing a reduction in risk for incident AF in such patients. This study is timely because there have been conflicting data on the association between physical activity and incident AF. The study shows a significant reduction in incident AF in obese post-menopausal women with high physical activity levels.

This study and its methodology were well-thought out, planned and executed. Some of the numerous strengths include a large sample size of 93 676 post-menopausal women were followed up for a period of 11.5 years. The large sample size of this study increases the power of the study. Appropriate statistical tool, the multivariate Cox's hazard regression model was used to adjust for demographic and clinical risk factors was used to evaluate the interaction between obesity and physical activity and its association with incident AF.

Obesity was evaluated with the use of BMI, a well known and validated tool for clinical assessment of obesity. Patient reported questionnaires on physical activity were also used to estimate activity level in such patients using the women health initiative (WHI) physical activity questionnaire. Both the BMI and WHI physical activity questionnaire are validated and reproducible screening tools. The study took into account other confounding factors such as age, co-morbidity like hypertension, diabetes mellitus, congestive heart failure, alcohol, smoking history etc

The writing was clear and concise. The abstract gives a snapshot of the objectives and the findings. The authors introduced the topic and gave the rationale for the study. The conclusion further emphasizes the finding and recommends physical activity as an essential factor in reduction of obesity ad AF risk in obese women.

The few weak points noted on this study includes the involvement of only post-menopausal women in the analysis. This study findings will be applicable to only women but not to men. It will beneficial to the general public to undertake such studies with inclusion of both men, women and younger age groups as well. This be helpful in the generalization and applicability of the findings.

Secondly, the body mass index (BMI) used in assessing obesity, though a well validated tool, also has its own limitations. The body mass index is unable to differentiate between fat from lean mass. It also does not capture the regional distribution of adiposity that may confer differential AF risk. Other measures of obesity such as waist circumference, abdominal girth may be helpful in distinguishing the regional distribution of fat in obese patients.