Does an Obesity Paradox Really Exist After Cardiovascular Intervention?: A Systematic Review and Meta-Analysis of Randomized Controlled Trials and Observational Studies

Several studies have shown the existence of an obesity paradox after Percutaneous Coronary Intervention (PCI). However, other studies have shown its absence. This study sought to perform a systematic review and meta-analysis of studies comparing the mortality risk between high body mass index patients and normal weight patients after PCI. We have searched PubMed, Embase, and Chinese medical journal for randomized controlled trials (RCTs) and observational studies published between the year 2000 and 2015 by typing the keywords “percutaneous coronary intervention” and “obesity paradox.” The main outcome was “all-cause mortality”. RevMan 5.3 software was used to calculate the risk ratio (RR) with 95% confidence interval (CI) to express the pooled effect on discontinuous variables. Twenty-two studies have been included in this meta-analysis consisting of a total of 242,377 patients with 73,143 normal weight patients, 103,608 overweight, and 65,626 obese patients. Younger age, higher cardiovascular risk factors and the intensive use of medications have mainly been observed among obese patients followed by overweight and normal weight patients respectively. In-hospital, 12 months and ≥ 1 year (long-term) mortality risks were significantly lower in the overweight and obese groups with (RR: 0.67; 95% CI: 0.63–0.72, P < 0.00001) and (RR: 0.60; 95% CI: 0.56–0.65, P < 0.00001) respectively in the in-hospital follow-up (RR: 0.62; 95% CI: 0.55–0.71 and 0.57; 95% CI: 0.52–0.63, P < 0.00001) at 12 months, and (RR: 0.70; 95% CI: 0.64–0.76; P < 0.00001) and (RR: 0.80; 95% CI: 0.71–0.91, P = 0.0006) respectively for the long-term follow-up after PCI. This “obesity paradox” does exist after PCI. The mortality in overweight and obese patients is really significantly lower compared to the normal weight patients. However, the exact reasons for this phenomenon need further exploration and research in the future.