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SOS study

Lower long-term drug costs for surgical patients

Twenty years follow-up shows lower drug costs after seven years for surgical patients
Mean hospital days were equal after seven years

Patients who have bariatric surgery use fewer medications to treat diabetes and cardiovascular disease resulting in lower overall drug costs, according to the latest paper from the Swedish Obese Subjects (SOS) study published in the Journal of the American Medical Association.

From year seven to 20, the surgery group incurred a mean annual drug cost of US$930; the control patients, US$1,123 (adjusted difference, −US$228; 95% CI, -US$335 to −US$121; p<0.001).

The analysis also revealed surgical patients visited the hospital more often. However, after seven years the mean number of hospital days between the groups was the same.

This analysis, conducted by researchers at Karolinska Institutet and the Sahlgrenska Academy, University of Gothenburg, Sweden, included 2,010 adults who underwent bariatric surgery and 2,037 matched controls recruited between 1987 and 2001. Inclusion criteria included BMI>34 in men and >38 in women.


Of the surgery patients, 13% underwent gastric bypass, 19% gastric banding, and 68% vertical-banded gastroplasty. Controls received conventional obesity treatment. Control patients received conventional obesity treatment.

Annual hospital days (follow-up years one to 20; data capture 1987-2009; median follow-up 15 years) and non-primary care outpatient visits (years two to 20; data capture 2001-2009; median follow-up nine years) were retrieved from the National Patient Register, and drug costs from the Prescribed Drug Register (years seven to 20; data capture 2005-2011; median follow-up six years).

Registry linkage was complete for more than 99% of patients (4,044/4,047). Mean differences were adjusted for baseline age, sex, smoking, diabetes status, BMI, inclusion period and (for the inpatient care analysis) hospital days the year before the index date.

In the 20 years following their bariatric procedure, surgery patients used a total of 54 mean cumulative hospital days compared with 40 used by those in the control group (adjusted difference, 15; 95% CI, 2-27; p=0.03). During the years two through six, surgery patients had an accumulated annual mean of 1.7 hospital days vs. 1.2 days among control patients (adjusted difference, 0.5; 95% CI, 0.2 to 0.7; p<0.001). From year seven to 20, both groups had a mean annual 1.8 hospital days (adjusted difference, 0.0; 95% CI, −0.3 to 0.3; p=0.95).

Surgery patients had a mean annual 1.3 non-primary care outpatient visits during the years two through six vs. 1.1 among the controls (adjusted difference, 0.3; 95% CI, 0.1 to 0.4; p=0.003), but from year seven, the two groups did not differ (1.8 vs 1.9 mean annual visits; adjusted difference, −0.2; 95% CI, −0.4 to 0.1; p=0.12).

Previous analyses of the SOS data have shown that surgically induced weight loss results in sustained weight loss, reduced incidence of diabetes, cardiovascular events and cancer, as well as improved ten- to 15-year survival.

The SOS study received funding from the Swedish Research Council, the Swedish Foundation for Strategic Research (SSF), and several pharmaceutical companies.

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