Two Studies Show that Obesity Surgery Does Improve Mortality Outcomes
by David W. Sharp

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There is as yet no established clinical specialty of bariatrics, but if worldwide obesity trends continue one may soon be needed. However, we do have bariatric surgery, which covers several different operative procedures on the stomach such as gastric banding. Surgery is usually a last resort and guidelines suggest that only exceptionally should it be resorted to if the patient’s body-mass index (or BMI, determined by weight in kilograms divided by the square of height in meters) is below 40. Obesity is defined by a BMI of 30 or more.

When the Swedish Obese Subjects (SOS) controlled but non-randomized follow-up study began in 1987 it would not have been certain that weight-reducing surgery would benefit mortality. The position would have been a little clearer by the time recruitment ended in early 2001. Even so, the central message of the main SOS paper, which was at #14 last time and has now inched up to #13 (L. Sjostrom, et al., New Engl. J. Med., 357[8]: 741-52, 23 August 2007; total cites 163, latest count 38) is important. Bariatric surgery for severe obesity was associated both with long-term weight loss and with reduced mortality. The surgery group numbered 2,010 and the matched controls (given non-standardized conventional treatments) 2,037.

After an average follow-up of almost 11 years, 6.3% of the controls had died  compared with 5.0% of the surgery group. There were very few early postoperative deaths (five within 90 days of surgery). The controls experienced no meaningful weight change but at 10 years the surgical patients had average losses of 14-25%, depending on the type of operation.

Science Watch asked Dr. Lars Sjostrom what influence this 2007 paper might have had on patient choices in Sweden and elsewhere. Sweden has a population of only 9 million, and in 2002 about 700 bariatric operations were done, says Dr. Sjostrom. At that time the figure for the USA would have been more than 100,000. In 2008 the Swedish figure had quadrupled to 2,800. Sjostrom reckons that referrals for such surgery have doubled in the past two or three years but does not know if this change reflects "increased pressure from obese patients or an increased interest from referring doctors."

Today’s BMI-above-40 criterion was not in place back in 1987, and in SOS the cutoffs were 34 for men and 38 for women. How important is this difference, Science Watch wondered? Not at all, it seems. The relative effect of surgery on mortality was no different for patients above and below the median BMI in these patients, which was 40.8. In Sjostrom’s opinion, "most obese patients with BMI 35 to 40 kg/m² will not obtain efficient lifelong treatment without bariatric surgery, given the current non-surgical treatment modalities available."

Those in the 35 to 40 BMI range have a poor health-related quality of life; in patients who are operated on, quality of life improves, and the greater the weight loss the more the improvement (J. Karlsson, et al., Int. J. Obesity, 31[ 8]: 1248-61, 2007). Finally, Science Watch touched on advances in surgical technique since 1987-2001, the years of recruitment to SOS, an example being laparoscopic ("keyhole") surgery. "Probably, we obtained the favorable results not due to but in spite of old-fashioned methodology," says Sjostrom. With today’s methods, the advantages of bariatric surgery might have been even greater.

Accompanying the SOS paper at #13 came data from a retrospective study of mortality in surgery patients and matched controls (T. D. Adams, et al., New Engl. J. Med., 357[8]: 753-61, 23 August 2007; 19 citations for this period, 108 overall) supporting the conclusions of Dr. Sjostrom and his colleagues. In this study, 7,925 patients undergoing gastric bypass surgery were compared with a matched number of obese patients applying for driving licenses.

After about seven years of follow-up, the mortality rate was lower in the surgical group (37.6 versus 57.1 deaths per 10,000 patient-years). A tendency for non-disease-related deaths to be higher in the surgery group does not appear in the SOS study. Again, quality of life improved with surgery (R.L. Kolotkin, et al., Surg. Obes. Related Dis., 5[2]: 250-6, March 2009).

A former deputy editor of The Lancet, Mr. David W. Sharp, M.A. (Cambridge), is a freelance writer living in Minchinhampton, U.K.

KEYWORDS: BARIATRIC SURGERY, WEIGHT-LOSS SURGERY, ANTI-OBESITY SURGERY, GASTRIC BYPASS, SWEDISH OBESE SUBJECTS, SOS STUDY, LARS SJOSTROM, BARIATRIC SURGERY AND MORTALITY, ROUX-EN-Y, QUALITY OF LIFE, BMI.