Body mass index and postoperative independence: a reply

We appreciate the interest from Liang [1] in our study on the association of BMI and recovery to independent living after non-cardiac surgery [2]. We are happy to provide the suggested additional analyses to discuss our findings further. Body mass index had a U-shaped association with both parts of the composite endpoint (Fig. 1 and online Supporting Information Table S1). Contrary to the hypothesis raised by Liang, the increased risk in mortality was somewhat more pronounced in patients with BMI > 40 kg.m-2, while the risk of discharge to a nursing facility was more pronounced in patients with BMI < 22 kg.m-2. However, the 95%CIs of the risk ratios for the different outcomes overlapped. In our cohort, there were 8064 (11%) patients with BMI of 18.5–22 kg.m-2, which is defined as ‘normal weight’ but was associated with an increased risk of adverse hospital discharge. These patients carried an absolute risk of adverse discharge of 18%, while patients with BMI of 22.1–25 kg.m-2 carried an absolute risk of 14% (online Supporting Information Table S2). We therefore agree with Liang that clinicians should focus on patients who have an increased complication risk and are potentially overlooked. Future studies may examine the effects of enhanced pre-operative assessment and prehabilitation of patients who present with BMI at the lower end of normal weight (18.5–22 kg.m-2). Table S1. Adjusted risk ratios for the combined outcome and separate outcomes. Table S2. More granular analysis for patients with ‘normal weight’. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.