Elevated Anemia Risk Even Years After Bariatric Surgery

By Lisa Rapaport

August 09, 2021

(Reuters Health) - People with obesity who undergo bariatric surgery may be more likely to experience anemia years later than counterparts who opt against surgery, a new study suggests.

Researchers examined data on patients with obesity who were eligible for bariatric surgery between Sept. 1, 1987, and Jan. 31, 2001, including 2,007 people who proceeded with operations and 2,040 matched controls who opted against the procedures. After a maximum follow-up of 20 years (median 10 years), the incidence of anemia per 1,000 person-years was 64 with gastric bypass, 26 with gastric banding, 23 with vertical banded gastroplasty, and 13 in the control group.

Compared with non-surgical controls, patients had a significantly greater incidence of anemia with gastric bypass (hazard ratio 5.05), gastric banding (HR 2.76) and vertical banded gastroplasty (HR 2.67), the researchers report in The Lancet Diabetes & Endocrinology.

"As bariatric surgery involves anatomical changes of the gastrointestinal tract it is not surprising that these rearrangements can lead to anemia and other nutritional deficiencies," said lead study author Kari Johansson of the Karolinska Institute in Stockholm, Sweden.

It's also not surprising that gastric bypass and other procedures that bypass the duodenum and the proximal part of the jejunum, the main absorption sites of iron, had the higher incidence rates of anemia, Johansson said by email.

"In addition to the anatomical changes of the procedures itself, the reduced intake of calories and thereby micronutrients, and changes in food preferences including meat and dairy intolerance, may further decrease the intake of iron and thereby lead to anemia," Johansson added.

Women appeared to have a greater risk of anemia after surgery than men in adjusted analysis that accounted for age, BMI, education, diabetes, hypertension, and menopausal status in women.

Compared to women who didn't get surgery, women were significantly more likely to experience anemia with gastric bypass (HR 6.50), gastric banding (HR 3.20), and vertical banded gastroplasty (HR 3.02).

Compared to men who didn't get surgery, men were also significantly more likely to experience anemia with gastric bypass (HR 3.03), gastric banding (HR 1.82), and vertical banded gastroplasty (HR 1.98).

One limitation of the study is that researchers lacked data on sleeve gastrectomy because they only had data on procedures commonly used in Sweden during the study period.

Another limitation is the lack of serum ferritin concentration data to classify iron deficiency anemia. Researchers were also unable to calculate the incidence of anemia with or without iron deficiency or anemia with or without B12 deficiency.

While bariatric surgery results in substantial and sustained health gain, clinicians need to remain vigilant regarding the small risk of long-term side effects including anemia, said Carel le Roux of the Diabetes Complications Research Centre at University College Dublin who coauthored a commentary accompanying the study.

"Routine monitoring of patients after bariatric surgery is not very complicated and most primary care doctors and hospital specialists can easily manage these patients," le Roux said by email. "Protocols for follow-up care have been established but patients should remain in long term follow-up after bariatric surgery."

SOURCE: https://bit.ly/2X4ZXu4 and https://bit.ly/2VuSpjr The Lancet Diabetes & Endocrinology, online July 1, 2021.