Bariatric surgery can result in increased risk of anaemia



There is an increased risk of anaemia after bariatric surgery, according to researchers from Sweden who analysed 20 years outcomes from the Swedish Obese Subjects study. They stated that these findings emphasise “the importance of long-term compliance to nutritional supplementation and monitoring to enable prevention and early detection of serious nutritional deficiencies after bariatric surgery.”

In their study, ‘Long-term risk of anaemia after bariatric surgery: results from the Swedish Obese Subjects study’, published in The Lancet Diabetes and Endocrinology, the researchers investigated the long-term risk of anaemia, iron and vitamin B12 deficiency anaemia, and vitamin B12 deficiency in patients who underwent bariatric surgery, the type of which was determined by the operating surgeon and a contemporaneously matched control group who received non-surgical obesity care that ranged from lifestyle advice to no treatment.

Participants’ haemoglobin concentration was measured during examination visits at baseline and at one year, two years, three years, four years, six years, eight years, ten years, 15 years and 20 years of follow-up. Anaemia was defined as a haemoglobin concentration of less than 120 g/L for women and 130 g/L for men. The primary, non-specified outcome was the incidence of anaemia, and was assessed in the as-treated population, which comprised only patients who received the actual treatment.

Between 1987 and January 2001, 2007 patients who chose bariatric surgery (266 in the gastric bypass group, 1365 in the vertical-banded gastroplasty group, and 376 in the gastric banding group) and 2040 matched controls who received usual obesity care, were included in the study. During a maximum of 20 years and a median of ten years (IQR 3–20) of follow-up, there were 133 anaemia events in the gastric bypass group, 359 in the vertical-banded gastroplasty group, 101 in the gastric banding group, and 261 in the control group.

The results revealed that compared with the control group (13 cases per 1000 person-years, 95% CI 11–14), the incidence of anaemia was higher in the gastric bypass group (64 cases per 1000 person-years, 53–74; HR 5·05, 95% CI 3·94–6·48; p<0·0001), the vertical-banded gastroplasty group (23 cases per 1000 person-years, 21–26; 2·67, 2·25–3·18; p<0·0001), and the gastric banding group (26 per 1000 person-years, 21–31; 2·76, 2·15–3·52; p<0·0001). These associations remained after adjustment.

“Our findings highlight the increased risk of anaemia after bariatric surgery and the importance of long-term compliance to nutritional supplementation and monitoring to enable prevention and early detection of serious nutritional deficiencies after bariatric surgery”, the authors concluded.

The study was funded by the Swedish Research Council, the Swedish state under the agreement between the Swedish Government and the county councils, the Swedish Diabetes Foundation, the Swedish Heart-Lung Foundation and the Novo Nordisk Foundation.

There is an increased risk of anaemia after bariatric surgery, according to researchers from Sweden who analysed 20 years outcomes from the Swedish Obese Subjects study. They stated that these findings emphasise “the importance of long-term compliance to nutritional supplementation and monitoring to enable prevention and early detection of serious nutritional deficiencies after bariatric surgery.”

In their study, ‘Long-term risk of anaemia after bariatric surgery: results from the Swedish Obese Subjects study’, published in The Lancet Diabetes and Endocrinology, the researchers investigated the long-term risk of anaemia, iron and vitamin B12 deficiency anaemia, and vitamin B12 deficiency in patients who underwent bariatric surgery, the type of which was determined by the operating surgeon and a contemporaneously matched control group who received non-surgical obesity care that ranged from lifestyle advice to no treatment.

Participants’ haemoglobin concentration was measured during examination visits at baseline and at one year, two years, three years, four years, six years, eight years, ten years, 15 years and 20 years of follow-up. Anaemia was defined as a haemoglobin concentration of less than 120 g/L for women and 130 g/L for men. The primary, non-specified outcome was the incidence of anaemia, and was assessed in the as-treated population, which comprised only patients who received the actual treatment.

Between 1987 and January 2001, 2007 patients who chose bariatric surgery (266 in the gastric bypass group, 1365 in the vertical-banded gastroplasty group, and 376 in the gastric banding group) and 2040 matched controls who received usual obesity care, were included in the study. During a maximum of 20 years and a median of ten years (IQR 3–20) of follow-up, there were 133 anaemia events in the gastric bypass group, 359 in the vertical-banded gastroplasty group, 101 in the gastric banding group, and 261 in the control group.

The results revealed that compared with the control group (13 cases per 1000 person-years, 95% CI 11–14), the incidence of anaemia was higher in the gastric bypass group (64 cases per 1000 person-years, 53–74; HR 5·05, 95% CI 3·94–6·48; p<0·0001), the vertical-banded gastroplasty group (23 cases per 1000 person-years, 21–26; 2·67, 2·25–3·18; p<0·0001), and the gastric banding group (26 per 1000 person-years, 21–31; 2·76, 2·15–3·52; p<0·0001). These associations remained after adjustment.

“Our findings highlight the increased risk of anaemia after bariatric surgery and the importance of long-term compliance to nutritional supplementation and monitoring to enable prevention and early detection of serious nutritional deficiencies after bariatric surgery”, the authors concluded.

The study was funded by the Swedish Research Council, the Swedish state under the agreement between the Swedish Government and the county councils, the Swedish Diabetes Foundation, the Swedish Heart-Lung Foundation and the Novo Nordisk Foundation.