Impact of age on the prognostic value of body mass index in ST-Elevation myocardial infarction.

BACKGROUND AND AIM: No data are so far available on the impact of age and obesity in ST-elevation myocardial infarction (STEMI) submitted to percutaneous coronary intervention (PCI). METHODS AND RESULTS: We assessed the impact of age on the prognostic value of body mass index (BMI) in 1268 consecutive STEMI patients admitted to our Intensive Cardiac Care Unit (ICCU). BMI categories were as follows: 37 "lean" patients (37/1268, 2.9%), 403 "normal" patients (403/1268, 31.8%), 656 "overweight" patients (656/1268, 51.7%), 172 "obese" patients (172/1268, 13.6%). Among patients aged <75 years, as BMI increased, the number of males and diabetic patients significantly increased (p < 0.001 and p = 0.004, respectively). Among STEMI patients aged ≥75 years, lean patients showed a higher in-ICCU mortality in respect to the other BMI categories but this did not reach statistical significance. BMI was an independent predictor of In-ICCU mortality in the whole population (lean vs. "normal": OR 3.47, 95%CI 1.08-11.14, p = 0.036) and it was associated with long term mortality only in patients <75 years since lean and overweight patients showed lower survival rate (lean vs. "normal": HR 9.25, 95%CI 3.09-27.63, p < 0.001; overweight vs. "normal": OR 2.10; 95%CI 1.04-4.23, p = 0.039). CONCLUSIONS: In our series, underweight is associated with the highest mortality across all age subgroups, while only in patients <75 years, overweight patients showed increased in-hospital mortality rate and a poorer long term survival rate. According to our data, the "so called obesity paradox" should be probably age-contextualized.