Abstract
The World Health Organization (WHO) defines obesity as a body mass index (BMI) of ≥ 30 kg/m2. Obesity has been established as an independent risk factor for new-onset atrial fibrillation (AF). Despite the association between obesity and major cardiovascular risk factors and outcomes, some studies showed that obesity may have a protective effect on AF-related outcomes, leading to the controversial concept of the ‘obesity paradox’. We carried out a systematic review to explore the ‘obesity paradox’, providing an overview of the randomized controlled trials (RCTs) and the impact of BMI on AF-related outcomes.
We performed an extensive literature search, from 2000 up to 2021, using the PubMed database, with two independent reviewers (M. F. and F.G.). Discrepancies were resolved by consensus with a senior researcher (D.M.). Studies were eligible if they were RCTs and included outcome comparisons (cardiovascular death, all death, stroke, and major bleeding) with allocation to BMI. We excluded from the analysis trials in which the number of events was not reported. The effect measures of each included study were calculated and reported as hazard ratio (HR) with 95% confidence interval (CI), visually presented in forest plots. A total of 683 studies were available for the analysis; 74 records were included after reading the title; after full reading 8 studies were eligible to be analysed. The meta-analysis of the eight selected randomized controlled clinical trials demonstrated a significantly lower risk of stroke or systemic embolism and all causes of death in obese patient (Figures 1 and 2). A meta-analysis on cardiovascular mortality was not conducted because this was reported only for three trials.
This meta-analysis demonstrated lower stroke and death risk with increasing BMI. Our meta-analysis included only data from RCTs. Observational studies rendered more conflicting results. Because of the few studies included, these apparently protective effects of obesity on the risk of stroke in patients with atrial fibrillation should still be interpreted with caution.
