In recent years, clinical researches in the field of obesity have revealed the term of obesity paradox. This term relates to the apparently counterintuitive phenomenon where obese patients with cardiovascular diseases seem to have a lower risk of short- and long-term adverse events (19). Our study aimed to assess the role of obesity (body mass index) in outcomes of anticoagulation among patients with non-valvular AF (NVAF) on oral anticoagulants regarding thromboembolic and bleeding complications. We divided enrolled patients into two groups (obese and non-obese) according to BMI.
In the current study, both categories of our patients had in-significant differences regarding clinical presentation and type of oral anticoagulants where the majority of patients on warfarin.
Paroxysmal pattern of AF was present in majority of patients. Both groups showed no significant difference as regard CHA2DS2-VASc score. In concordance with our results, Inoue et al and Badheka et al reported that no significant difference regarding anticoagulation was detected among different BMI categories (21, 7). In contrast to our findings, Inoue et al showed a higher frequency of permanent AF among obese patients. They also, found that CHA2DS2-VASc and CHA2DS2 scores were significantly higher among underweight patients (21).
Our study focused on four outcomes among patients with NV-AF including; bleeding, cerebrovascular stroke, deep venous thrombosis, and cardiovascular death. We found that, non-obese patients had higher frequency of complications compared to obese patients.
To date, several studies have investigated the relationship between obesity and occurrence of MACEs among AF patients (7, 21, 22, 23, 24).Since then, evidence regarding research about the obesity paradox among AF patients has been noticeably conflicting. Indeed, most studies had shown an independent association, with low risk of stroke, cardiovascular death, and all-cause death for overweight and obese patients (19).However, results from observational and population-based cohort studies testing the obesity paradox hypothesis had been controversial (19). Our study reported five predictors for complications among NV-AF patients including: DM, HTN, dyslipidemia, smoking and CHA2DS2-VASc Score > 2 according to multivariate regression analysis model while obesity wasn't found to be a good predictor.
The first study to propose an obesity paradox among AF patients was published by Badheka et al. According to their findings, being overweight or obese was linked to a lower chance of dying from heart disease, any cause, or a composite endpoint of all MACEs. Additionally, a multivariate regression study using BMI as a continuous variable discovered that the probability of dying from any cause gradually decreased for each 1 kg/m2 increase in BMI (7).
Obesity and overweight are linked to a lower risk of stroke/systemic embolism and all-cause mortality, according to a recent subgroup analysis. Additionally, a composite net result shows an independent relationship between higher BMI (for every 5 kg/m2 rise) and a lower risk of the same occurrences (22).
These conclusions were challenged by a second meta-analysis by Proietti et al and by a third meta-analysis by Zhou et al, performed mostly by pooling data from randomized clinical trials (RCTs), that consistently showed that patients with higher BMI had a lower risk of stroke occurrence (25, 26) in agreement with Liu et al who showed that overweight and obesity were associated with less adverse outcomes among AF patients (24).
Our study supported all previous findings and concluded that obese patients were less vulnerable to develop complications regarding bleeding ,cerebrovascular stroke and cardiovascular death compared to non -obese patients.
In contrast to our results, Overvad et al, European society of cardiology and a systematic review and meta-analysis investigating the obesity paradox among AF patients, concluded that the risk for adverse outcomes among overweight and obese AF patients was substantially similar to that among normal-weight AF patients (20, 22, 27).
The phenomenon known as the obesity paradox has been the subject of numerous reflections. The average patient age decreased with rising BMI class in the majority of trials. Additionally, individuals who were overweight or obese typically had more comorbidities than those who were of a healthy weight (28). Patients who were overweight or obese were also more likely to be prescribed medications for medical disorders, particularly those pertaining to the management of cardiac and cardiovascular conditions and the avoidance of associated hazards. Given this, our hypothesis is that patients who are overweight or obese typically receive treatment earlier, with a more rigorous pharmacological approach, and with tighter and longer-term follow-up than patients who are of normal weight (5). These and other factors are thought to be possible explanations for the obesity paradox, both generally and among AF patients, and it should be noted that, It is difficult to take into account every potential element influencing outcomes, especially in multivariate analysis (5).
Finally, the idea of "metabolically healthy obese" (MHO) patients has been proposed as another potential mediating mechanism for the obesity paradox. This phrase describes individuals who, despite being obese, have a healthy metabolic profile and are physically active (5).
MHO patients had a much lower (and non-significant) chance of negative outcomes, according to numerous studies. A similar clinical profile has also been linked to an unusual and distinct adipose tissue biology that appears to reduce the likelihood of serious adverse outcomes (5, 29).
Despite all the evidence, the European Society of Cardiology's recommendations for managing AF included patient empowerment and proper education; in obese individuals, essential objectives for lowering the burden and symptoms of AF and for improving outcomes included weight loss in conjunction with management of other risk factors (30).
Finally, our studies assessed the relationship between BMI and oral anticoagulants and related outcomes. We noticed that the use of DOACS was more beneficial among obese patients regarding associated complications. In consistent with our results, Zhou et al found that a slightly beneficial effect of DOAC treatment was found among overweight patients (26). But in contrast, Proietti et al found a clear advantage for DOACs compared with VKAs among normal weight patients for both stroke and major bleeding occurrence (25). Generally, by analyzing reported studies, there were controversial data that can be obtained about the variable effect of the different types of OACs according to BMI class (19).
The debates around the obesity paradox should not discourage efforts to promote healthy weight loss methods and increase physical activity and exercise. According to international experts on health, weight, and obesity, these continue to be completely supported by the general unfavourable effects of being overweight or obese and should be promoted for both AF patients and the general public. On the other hand, greater research and explanation are still needed for the obesity paradox in cardiovascular medicine.