Despite ongoing reports that bariatric surgery successfully treats extreme obesity, increasing concerns about the adverse effects of the surgery are prompting further research.

Researchers conducted a prospective, multicenter study of 4,776 patients undergoing first-time bariatric surgery between 2005 and 2007. The composite end point of the study was death, deep-vein thrombosis or venous thromboembolism, surgical reintervention, or no hospital discharge within 30 days after surgery.

Most patients underwent laparoscopic Roux-en-Y gastric bypass surgery. The most prevalent concomitant conditions were hypertension, obstructive sleep apnea, diabetes, and asthma. Median body mass index was 46.5, with a high of 50.9 in patients who had open surgery.

Just 4.1% of the 4,610 patients analyzed experienced the composite end point, and the 30-day mortality rate was only 0.3%. But patients had an increased risk of the end point if they had a history of deep-vein thrombosis or venous thromboembolism, a diagnosis of obstructive sleep apnea, impaired functional status, or an extremely high body mass index. Other characteristics, such as age, sex, race, ethnic group, and other concomitant conditions didn't significantly affect the patients' risk.