Which Factors Are Associated with a Higher Prevalence of Anemia Following Bariatric Surgery? Results from a Retrospective Study Involving 1999 Patients.

INTRODUCTION: Anemia in obese patients is common and multifactorial and is also a complication of bariatric surgery. The aim of this study is to establish which variables are associated with a higher prevalence of post-bariatric surgery anemia. METHODS: Retrospective cohort study involving 1999 patients submitted to bariatric surgery with a follow-up period of 4 years. Anthropometric, laboratorial parameters and the presence of comorbidities were evaluated before surgery and during follow-up. Patients were divided into two groups, according to whether they developed anemia, or not. Groups were compared using independent sample T-tests or Chi-squared tests, as appropriate. Univariate binary logistic regression models were used to test the association between the diagnosis of anemia during follow-up and all the possible explanatory variables. Independent variables with an association with the outcome (p < 0.1) were included in multivariate binary logistic regression models, as well as possible confounders (age, BMI, and supplementation). RESULTS: Anemia was diagnosed in 24.4% of the patients. Females present a two-fold increased risk of developing anemia (OR 2.11, 95% CI 1.48-3.01, p < 0.001). Patients subjected to gastric sleeve and gastric band surgery present approximately half the risk of anemia when compared with gastric bypass surgery (RYGB) (OR 0.46, 95% CI 0.35-0.59, p < 0.001; OR 0.51, 95% CI 0.36-0.72, p < 0.001). None of the other variables evaluated showed association with the outcome. CONCLUSION: In our study, the only factors associated with an increased risk of developing anemia were female gender and RYBG surgery. Prospective studies evaluating the risk factors for anemia in patients undergoing bariatric surgery are needed.

Variable Thresholds of Vitamin D Plasma Levels to Suppress PTH: the Effect of Weight and Bariatric Surgery.

BACKGROUND: Serum 25-hydroxyvitamin D [25(OH)D] and parathormone (PTH) have an inverse relation. The 25(OH)D threshold required to maximally suppress PTH has been used as a marker of optimal vitamin D status. Obesity is associated with lower serum levels of 25(OH)D and higher levels of PTH; however, the relation between these hormones in this setting is not well established. We aimed to assess the influence of excessive weight and weight loss after bariatric surgery on the relation between serum 25(OH)D and PTH. METHODS: Anthropometric and analytical parameters of phospho-calcium metabolism from 290 patients undergoing bariatric surgery were analyzed. The association between 25(OH)D and PTH before and 1 year after surgery was evaluated through Student's t test and simple and multivariable linear regression. RESULTS: At baseline, there was an inverse association between 25(OH)D and PTH plasma levels (ß = - 0.571; p = 0.001). The threshold for a significant increase of PTH at baseline was a 25(OH)D level of < 10 ng/mL (p < 0.001). At 1 year after surgery (n = 194), the association between the two variables was weaker (ß = - 0.291; p = 0.014). The 25(OH)D threshold for a significant increase in serum PTH levels was lower in patients who maintained obesity (n = 77) [25(OH)D 5 vs 10 ng/mL]. CONCLUSIONS: PTH suppression threshold observed in patients with morbid obesity before and after bariatric surgery is lower than that described for the general population, suggesting that the 25(OH)D plasma levels may not be representative of the body's vitamin D reserves. Other studies are required to demonstrate which optimal vitamin D levels need to be aimed for in obesity, in order to improve obese patients' bone health.