Degree of Cardiometabolic Risk Factor Normalization in Individuals Receiving Bariatric Surgery: Evidence From NHANES 2015–2018

Abstract

Bariatric surgery leads to clinically significant weight loss and improvements in cardiometabolic risk factors (1–3).However, population-based evidence evaluating the degree of improvements in cardiometabolic outcomes among those receivingbariatric surgery is limited.Using the National Health and Nutrition Examination Survey (NHANES) 2015–2018, we examined cardiometabolic risk factors among individuals who had undergone bariatric surgery, those eligible for but not receiving bariatric surgery, and normal-weight adults. This study included adults aged $18 yearswho responded to bariatric surgery questions during the NHANES 2015–2018 cycles. TheNHANESuses a stratifiedmultistage probability method to sample the nationally representative U.S. population (https://www.cdc.gov/nchs/nhanes/ index.htm).Weanalyzed six cardiometabolic measuresdsystolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin A1c (HbA1c), total cholesterol (TC), HDL cholesterol (HDL-C), and hs-CRPdmeasured in a mobile examination center. We used survey design–adjusted descriptive statistics to characterize the study population into three groups: 1) individuals with normal weight (BMI 18.5–24.9 kg/m), 2) individuals reporting receipt of bariatric surgery, and 3) individuals medically eligible for bariatric surgery but reporting they had not received it. Surgery eligibility criteria include BMI$40 kg/m or BMI$35 kg/m and one or more obesity-related comorbidity (4). Rao-Scottx testswere used to compare the study group characteristics. For the main analyses, propensity score weighting (5) was used to minimize selection bias of receiving bariatric surgery using potential confounding factors given in Table 1 (except current BMI). We then fitted general linear models to compare levels of cardiometabolic outcomes between groups. All analyses were conducted with SAS 9.4 and considered an adjustedP,0.05formultiplecomparisons to be significant. This study was deemed exempt from review by the University of Florida Institutional Review Board because we used deidentified, publicly available data. Of 6,274 participants (mean age 49.8 years, 55.4% women, 64.9% White), 132 (2.1%) reported having bariatric surgery and 2,698 (43.0%) were eligible for bariatric surgery. Compared with normal-weight individuals, those receiving bariatric surgery were more likely to be older, female, White, and highly educated and to have higher family income. After the propensity score weighting, there were no significant differences in these characteristics. Despite significantly lower BMI among individuals with normal weight (22.3 kg/m) relative to individuals receiving bariatric surgery (34.9 kg/m), SBP, DBP, HbA1c, TC, and hs-CRP were not significantly different between groups (Table 1). Individuals who were eligible for bariatric surgery but did not have it had significantly higher levels of SBP, DBP, HbA1c, and hs-CRP and lower HDL-C compared with normal-weight individuals. As sensitivity checks, we tested the robustness of the main findings by including individual characteristics as covariates and excluding individuals diagnosed with diabetes or heart diseases from the analytic sample. Results remained consistent across groups. This population-based study included a weighted sample size of 3.6 million adults who reported receiving bariatric surgery. No statistically significant differences in numerous cardiometabolic risk factors were observed between normalweight and bariatric surgery groups, despite those having received bariatric surgery having BMI values in the obesity range. Moreover, cardiometabolic risk factors in individuals reporting having