Prevalence of anemia and related nutrient deficiencies after sleeve gastrectomy: A systematic review and meta‐analysis

Summary This study aimed to investigate the prevalence of anemia and related nutrient deficiencies after sleeve gastrectomy (SG). Four online databases were searched for relevant articles. Thirty‐one studies with 7639 patients were included in the meta‐analysis. The pooled anemia prevalence was 7%, 6%, 9%, 10%, 12%, 25%, 20%, and 18% at baseline, 3 months, 6 months, 12 months, 24 months, 36 months, 48 months, and 60 months, respectively. Although the prevalence of vitamin B12 and folate deficiencies remained low postoperatively, the prevalence of ferritin deficiency steadily increased from 6% at baseline to 27% at 60 months. The prevalence of serum iron deficiency decreased from 13% at baseline to 6% at 24 months and increased to 20% at 60 months. Anemia and ferritin deficiency were strongly correlated (Pearson correlation coefficient = 0.774, p = 0.041). Subgroup analysis suggested that age ≤40 years, preoperative anemia, and insufficient iron supplementations were high‐risk factors for postoperative anemia. SG is associated with an increased risk of anemia and decreased iron storage over long‐term observation. Routine iron supplementations may reduce anemia after SG; however, the dosages recommended by current guidelines may be insufficient. More strict monitoring schedules and supplementation strategies should be established for the timely detection and management of postoperative anemia.