The Effect of Body Mass Index on Complications from Cardiac Surgery in the Oldest Old

OBJECTIVES: Overweight (body mass index (BMI)>25) and obesity (BMI>30) are associated with adverse outcomes in the general population. In older people, an increased risk of adverse events was observed in leaner and overweight older subjects. We evaluated the association between BMI and cardiac surgery complications in subjects aged 75 and older. DESIGN: Retrospective review of complication rates compiled as part of the New York State Department of Health Adult Cardiac Surgery Report. SETTING: Academic tertiary care medical center. PARTICIPANTS: One thousand four hundred forty-eight subjects aged 75 and older who underwent cardiac surgery in an academic hospital between 1991 and 1999. MEASUREMENTS: Subjects were divided into tertiles based on their BMI. Logistic regression was used in multivariate analyses examining the association between tertiles of BMI (<23, 23-26,>26) and complications from cardiac surgery, adjusting for age and gender or using a full model adjusting for history of diabetes mellitus, hypertension, myocardial infarction (MI), congestive heart failure, smoking, chronic obstructive pulmonary disease, peripheral vascular disease, renal disease, surgical priority, age, and gender. RESULTS: Mean age was 79 (range 75-94); 58% of the subjects were male. The incidence of any postoperative complication, respiratory failure, or death was U-shaped, with higher incidence in the first tertile of BMI, followed by the last tertile and then the middle tertile. Subjects in the lowest tertile of BMI in the full model had a higher adjusted risk of stroke (odds ratio (OR) = 1.58, 95% confidence interval (CI) = 0.96-2.59), bleeding (OR = 1.71, 95% CI = 0.79-3.67), respiratory failure (OR = 1.65, 95%CI = 0.95-2.87), cardiovascular complications (stroke, MI, arrhythmia) (OR = 1.59, 95% CI = 0.93-2.73), and all complications (OR = 1.45, 95% CI = 1.05-2.00) than subjects in the middle tertile. The risk of most complications in subjects in the highest tertile of BMI was similar to that of subjects in the middle tertile except for wound infections (OR = 3.51, 95% CI = 0.92-13.33). The risk of death was higher in subjects in the lower tertile of BMI (OR = 1.97, 95% CI = 1.12-3.44) than in subjects in the middle tertile. The association between BMI and adverse cardiac surgical outcomes was stronger in men than women and decreased with advancing age. CONCLUSIONS: In the geriatric population, subjects with lower BMI have a higher risk of complications and death from cardiovascular surgery than subjects with higher BMI. An increased BMI does not increase the risk of complications from cardiovascular surgery, with the exception of wound infections.