Racial/ethnic disparities in nutritional deficiencies related to anemia after bariatric surgery
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BACKGROUND: Bariatric surgery is effective for weight loss, but is associated with deficiencies of several micronutrients. Among these, deficiencies in iron and vitamin B12 have been well-described in the literature. While it is known that blood levels of several micronutrients differ between racial groups, it is currently unknown whether the impact of bariatric surgery on micronutrient levels is also race-specific. We addressed this question in reference to vitamin B12 and iron because of the known racial differences in these micronutrients and their impact on red blood cell indices. The aim of our study was to determine whether there are differences in levels of ferritin and vitamin B12, as well as in hemoglobin (HGB) and hematocrit (HCT) levels, between African-Americans (AA), Hispanic-Americans (HA), and Caucasian-Americans (CA) after Roux-en-Y gastric bypass (RYGB) surgery. METHODS: A retrospective medical record review of 1,046 (201 AA, 106 HA, and 344 CA), who underwent bariatric surgery at Boston Medical Center (BMC) between 2004 and 2015 was conducted. Analysis of variance and linear mixed modeling was used to compare adjusted mean changes in biomarkers of anemia, vitamin B12, and ferritin between racial groups before RYGB and up to a period of 4+ years after the surgery. RESULTS: There were significant decreases in all racial/ethnic groups in mean HCT and HGB within the first year following surgery. Mean HCT from baseline to time point 1 (6months-1 year post-operatively) decreased by 3.3% for AA’s (p<0.001), 3.2% for HA’s (p<0.001), and 5% (p<0.001) for CA’s. Mean HCT and mean HGB for the entire sample decreased from baseline to the end of the observation period by 4.4% and 1.45 g/L, respectively. AA's had lower levels of HCT and HGB throughout the observation period compared to HA's and CA's in both the unadjusted and adjusted models. CA's had the highest levels of these blood markers. Decreases in ferritin were also significant, with a decrease from baseline to the end of the observation period of 27.8 μg/L for AA's (p=0.004), a decrease of 49.6 μg/L for HA's (p<0.001), and 54.5 μg/L (p<0.001) for CA's. In comparison with HA's and AA's, CA's had a higher ferritin level at baseline (p=0.715 and p=0.028, respectively). However, when adjusted for age, sex, and initial BMI, CA's had lower ferritin levels throughout much of the observation period compared to HA's and AA's. After an initial increase at 6 months- 1 year post-operatively (time point 1), mean B12 levels remained fairly stable throughout the observation period with levels only slightly declining for AA’s and HA’s over the observation period. Levels remained higher than baseline for all racial/ethnic groups with mean B12 levels at the end increasing by 144.6 ng/L for AA’s (p<0.001), 70.4 ng/L for HA’s (p=0.186), and 182.2 ng/L for CA’s (p<0.001). Though CA’s saw the greatest increase in mean B12 levels from baseline, AA’s had the highest mean B12 levels over the entire observation period, with significantly different levels compared to HA’s and CA’s at time points 1 (p=0.003 and p=0.028, respectively) and 3 (p=0.050 and p=0.042, respectively). Additionally, when other factors significantly affecting mean HCT, HGB, ferritin, and B12 were analyzed and adjusted for in the mixed model, AA’s continued to have the lowest HCT and HGB levels throughout much of the observation period, with CA's having the highest mean levels. For mean B12, even after adjusting for pre-BMI and sex, levels remained highest in AA’s compared to HA’ and CA’s. CONCLUSIONS: Our data demonstrate that ferritin levels, as well as red blood cell indices, decrease after RYGB and blood markers of anemia occur despite supplementation and post-operative follow-up care. We also show that ethnic minorities exhibit more exaggerated decreases in HCT and HGB, suggesting greater risk of anemia after RYGB in these groups. Thus, it is critical to consider race/ethnicity when providing treatment for patients undergoing gastric bypass surgery. However, future prospective studies are needed to further the preliminary results of this study.
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