Clinical outcomes after bariatric surgery: a five-year matched cohort analysis in seven US states

Abstract

Background: Bariatric surgery is the most effective weight loss treatment, yet few studies have reported on short- and long-term outcomes postsurgery.

Methods: Using claims data from seven Blue Cross/Blue Shield health plans serving seven states, we conducted a non-concurrent, matched cohort study. We followed 22,693 persons who underwent bariatric surgery during 2003-2007 and were enrolled at least 6 months before and after surgery. Using logistic regression, we compared serious and less serious adverse clinical outcomes, hospitalizations, planned procedures, and obesity-related co-morbidities between groups for up to 5 years.

Results: Relative to controls, surgery patients were more likely to experience a serious [odds ratio (OR) 1.9; 95% confidence interval (CI) 1.8-2.0] or less serious (OR 2.5, CI 2.4-2.7) adverse clinical outcome or hospitalization (OR 1.3, CI 1.3-1.4) at 1 year postsurgery. The risk remained elevated until 4 years postsurgery for serious events and 5 years for less serious outcomes and hospitalizations. Some complication rates were lower for patients undergoing laparoscopic surgery. Planned procedures, such as skin reduction, peaked in postsurgery year 2 but remained elevated through year 5. Surgery patients had a 55% decreased risk of obesity-related co-morbidities, such as type 2 diabetes, in the first year postsurgery, which remained low throughout the study (year 5: OR 0.4, CI 0.4-0.5).

Conclusions: While bariatric surgery is associated with a higher risk of adverse clinical outcomes compared to controls, it also substantially decreased obesity-related co-morbidities during the 5-year follow-up.

Fig. 1

Flow diagram showing identification of study subjects. Asterisk We had bariatric surgery cases from all seven plans from 2002 through 2005 (N=30,965), but only had two plans with cases in 2006 (N=5,345), and only one plan with cases in 2007 and 2008 (N=7,378). Dagger One site sent enrollees for conditions as specified but selected a 50% random sample of enrollees with hyperlipidemia due to the large number of enrollees with this condition. Double dagger The four age groups were 18–29, 30–44, 45–64, and ≥65 years old

Fig. 2

Adjusted odds ratio of outcomes, procedures, and diagnoses by time postsurgery in bariatric surgery versus matched comparison group. It depicts the adjusted odds ratios for the entire bariatric surgery group versus the matched comparison group for each year post-surgery. For instance, year 2 postsurgery is the odds ratio of the outcome in between year 1 and 2 postsurgery. Odds ratios are adjusted for age, gender, propensity to be obese, plan site, months enrolled in the plan, comorbidity, and whether the subject had an outcome of interest in the one year prior to surgery. The specific outcomes considered for each of the overall groupings are listed in Appendix Tables 3–6. Yr year, OR odds ratios, CI confidence intervals. The numbers for analysis by year in the surgery and control group are: N=22,693 for the first year per group, N=13,889 in the second year per group, N=7,982 in the third year per group, N=4,339 in the fourth year per group and N=2,108 in the fifth year per group comparison group by year 3. While the point estimate remained lower in the surgery group for years 4 and 5, the difference between groups was not statistically significant.

Fig. 3

Adjusted odds ratio of outcomes, procedures, and diagnoses by time postsurgery in open versus laparoscopic surgery groups. It depicts the adjusted odds ratios for the open surgery group versus the laparoscopic surgery group for each year post surgery. Lap-adjustable banding surgeries were excluded since this only occurs in the laparoscopic group and would have biased the analyses. Odds ratios are adjusted for age, gender, propensity to be obese, plan site, months enrolled in the plan, comorbidity, type of surgery, and whether the subject had an outcome of interest in the 1 year prior to surgery. The numbers for analysis in the open surgery group by year are 10,567 in the first year, 9,942 in the second year, 4,973 in the third year, 3,283 in the fourth year, and 1,778 in the fifth year. The numbers for analysis in the laparoscopic group by year are 9,572 in the first year, 7,061 in the second year, 2,512 in the third year, 871 in the fourth year, and 330 in the fifth year. Yr year, OR odds ratios, CI confidence intervals