Underweight and obesity are related to higher mortality in patients undergoing coronary angiography: The KARDIO invasive cardiology register study.

Background: In patients with some cardiovascular disease conditions, slightly elevated body mass index (BMI) is associated with a lower mortality risk (termed "obesity paradox"). It is uncertain, however, if this obesity paradox exists in patients who have had invasive cardiology procedures. We evaluated the association between BMI and mortality in patients who underwent coronary angiography.

Methods: We utilised the KARDIO registry, which comprised data on demographics, prevalent diseases, risk factors, coronary angiographies, and interventions on 42,636 patients. BMI was categorised based on WHO cut-offs or transformed using P-splines. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated for all-cause mortality.

Results: During a median follow-up of 4.9 years, 4688 all-cause deaths occurred. BMI was nonlinearly associated with mortality risk: compared to normal weight category (18.5-25 kg/m ), the age-adjusted HRs (95% CIs) for all-cause mortality were 1.90 (1.49, 2.43), 0.96 (0.92, 1.01), 1.04 (0.99, 1.09), 1.08 (0.96, 1.20), and 1.45 (1.22, 1.72) for underweight (<18.5 kg/m ), preobesity (25 to <30 kg/m ), obesity class I (30 to <35 kg/m ), obesity class II (35 to <40 kg/m ), and obesity class III (>40 kg/m ), respectively. The corresponding multivariable adjusted HRs (95% CIs) were 2.00 (1.55, 2.58), 0.92 (0.88, 0.97) 1.01 (0.95, 1.06), 1.10 (0.98, 1.23), and 1.49 (1.26, 1,78), respectively.

Conclusions: In patients undergoing coronary angiography, underweight and obesity class III are associated with increased mortality risk, and the lowest mortality was observed in the preobesity class. It appears the obesity paradox may be present in patients who undergo invasive coronary procedures.