Impact of Body Mass Index on Cardiac Arrest Outcomes: A Systematic Review and Meta-Analysis

The influence of an individual's body mass index (BMI) on cardiac arrest outcomes remains uncertain. The aim of this study is to evaluate the impact of BMI categories (underweight, normal BMI, overweight, and obese) on mortality and neurological outcomes in patients experiencing cardiac arrest. We comprehensively searched standard electronic databases (PubMed, EMBASE, and Scopus) for relevant observational studies published in peer-reviewed journals written in English. We calculated pooled effect estimates using random-effects models and reported them as odds ratios (ORs) with 95% confidence intervals (CIs). We included 20 studies in our meta-analysis. Individuals with normal BMIs and those who were underweight had similar risks of in-hospital mortality (OR, 1.20; 95% CI, 0.90-1.60), mortality within 6 months of discharge (OR, 0.92; 95% CI, 0.59-1.42), mortality after the 1-year follow-up (OR, 2.42; 95% CI, 0.96-6.08), and odds of favorable neurological outcomes at hospital discharge (OR, 0.86; 95% CI, 0.53-1.39) and at the 6-month follow-up (OR, 0.73; 95% CI, 0.47-1.13). The risks of in-hospital mortality and mortality within 6 months of discharge in overweight and obese individuals were similar to those in individuals with normal BMIs. However, overweight (OR, 0.57; 95% CI, 0.35-0.92) and obese individuals (OR, 0.67; 95% CI, 0.51-0.89) had lower risks of mortality after their 1-year follow-ups. For overweight and obese subjects, the reduced risk of mortality after the 1 year of follow-up was noted only for those with in-hospital cardiac arrest and not for those with out-of-hospital cardiac arrest. The odds of favorable neurological outcomes in both overweight and obese individuals were similar to those with normal BMIs. BMI does not significantly impact short-term mortality or neurological outcomes. Overweight and obese individuals appear to have a lower risk of long-term mortality, but this differed by the place of arrest and needs to be confirmed by others.