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Ann Thorac Surg 2007;84:720-722
© 2007 The Society of Thoracic Surgeons

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Editorials

Obesity and Stroke After Cardiac Surgery: The Impact of Grouping Body Mass Index

^a Institute for Health Care Research and Improvement, Baylor Research Institute, Dallas, Texas
^b Department of Statistical Science, Southern Methodist University, Dallas, Texas
^c Cardiology Research Clinic, Dallas, Texas
^d Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, Texas

^_* Address correspondence to Dr Filardo, Institute for Health Care Research and Improvement, 8080 N Central Expressway, Suite 500, Dallas, TX 75206 (Email: giovanfi@baylorhealth.edu).

The first 300 words of the full text of this article appear below.

Factors associated with morbidity and mortality after isolated coronary artery bypass graft surgery (CABG) have been extensively investigated, yet uncertainty regarding the risk associated with obesity (or cachexia) and a number of postoperative adverse outcomes remains [1–15]. For the most part, research focused on describing the relationship between body mass index (BMI), as a proxy for body fatness, and post-CABG adverse events using a wide variation of pre-defined categorizations (eg, the World Health Organization or the American Heart Association) or using arbitrary BMI categorizations [2–15]. Typically such studies described the relationship between BMI and a broad spectrum of postoperative adverse outcomes (eg, stroke, operative mortality) using the same BMI categorization for all the outcomes [2–15]. However, the shape of the association between BMI and each of the postoperative adverse outcomes is unique, and ignoring this during data analysis (ie, using a single BMI categorization to investigate all adverse outcomes) can critically affect study results [16–19]. Moreover, grouping BMI into classes carries serious dangers in itself, as categorization can bias inference regarding BMI and post-CABG morbidity and mortality [16, 17, 19–21]. We hypothesize that BMI categorization may be one cause of the inconsistent findings regarding the association between obesity and cachexia and adverse outcomes after cardiac surgery.

To investigate this hypothesis, we considered the relationship between BMI and the risk of stroke after CABG. We conducted literature searches using PubMed to gather studies that have reported on this topic. Search strategies were formulated to retrieve records published in English that combined terms related to BMI, isolated CABG, and stroke. Articles listed in the references of the identified reports were also considered for a review of the statistical methods and results (see Table 1). All the identified studies [2–13, 15. . . [Full Text of this Article]