Bariatric Surgery Is Associated with a Significant Reduction in 10-Year Cardiovascular Risk

Abstract

Introduction:

Bariatric surgery is the only evidence-based method of long-term weight control in obese individuals. The reduction in individual cardiovascular risk following bariatric surgery has not yet been quantified. QRISK2 is a United Kingdom-designed algorithm that predicts 10-year cardiovascular risk. In this study, we calculated the QRISK2 scores for patients before and after bariatric surgery in an effort to assess cardiovascular risk reduction following bariatric surgery objectively.

Materials and Methods:

We reviewed all patients who had undergone bariatric surgery over a 10-year period (June 2003–June 2013) at our institute. QRISK2 score was calculated pre- and postoperatively for all patients. The postoperative score was calculated at the point of longest available follow-up.

Results:

A total of 250 patients were included, with a median age of 36 years (interquartile range 29–44). Median follow-up postoperatively for all patients was 24 months (interquartile range 6–36). A hundred patients underwent sleeve gastrectomy, 67 (26.8%) patients had biliopancreatic diversion (BPD), 50 (20%) patients had a Roux-en-Y gastric bypass (RYG), and 33 (13.2%) were fitted with gastric bands. The median preoperative QRISK2 score was 5.6%; the median postoperative QRISK2 score was lower at 4.4% (p<0.001).

Conclusion:

This study is the first to use a validated scoring system to assess 10-year cardiovascular risk reduction in bariatric patients. We have demonstrated a significant reduction in cardiovascular risk following bariatric surgery.

Introduction

The incidence of morbid obesity and specifically metabolic syndrome continues to rise in the United Kingdom, with the prevalence of obesity doubling in the last quarter of a century.¹ It is estimated that by 2025, as many as 40% of the United Kingdom population will be obese,² and this figure will rise to 90% in children born in 2007 by 2050.¹

Conservative measures to tackle obesity generally prove futile, and bariatric surgery remains the only evidence-based strategy to achieve long-term weight control.³ In addition to substantial weight loss, surgery is associated with a significant improvement in obesity-related comorbidities, particularly type II diabetes and hypertension,^3,4 with as many as three-quarters of patients with pre-existing diabetes achieving long-term glycemic control.⁵

Despite sporadic reports of improvement in cardiovascular status, the reduction in individual cardiovascular risk following surgery has not yet been quantified. QRISK2 is a United Kingdom designed, validated, and widely used algorithm to predict cardiovascular risk over a 10-year period.^6,7 QRISK2 is calibrated specifically for a United Kingdom population and is an alternative to the more widely used Framingham Risk Score.⁷ In this study, we calculated the QRISK2 scores for patients before and after bariatric surgery at our institute in an effort to assess cardiovascular risk reduction following bariatric surgery objectively.

Materials and Methods

All patients undergoing bariatric surgery over a 10-year period (June 2003–June 2013) at our institute were studied using the Welsh Institute of Metabolic and Obesity Surgery (WIMOS) database.

All demographic and cardiovascular risk data were obtained, and the QRISK2 score was calculated pre- and postoperatively for all patients. The postoperative score was calculated at the point of longest available follow-up duration.

Data were analyzed with a nonparametric Mann–Whitney U-test using SPSS v16 (SPSS, Inc., Chicago, IL). Statistical significance was calculated at p≤0.05.

Results

Two hundred and fifty patients were studied, of which 184 were female. The median age was 36 years (interquartile range 29–44 years). The majority of patients (n=100; 40.0%; 70 female) underwent a laparoscopic sleeve gastrectomy (LSG), 67 (26.8%; 45 female) a biliopancreatic diversion (BPD), 50 (20%; 39 female) a laparoscopic Roux-en-Y gastric bypass (LRYGB), and 33 (13.2%; 30 female) a laparoscopic adjustable gastric band (LAGB). The median follow-up postoperatively for all patients was 24 months (interquartile range 6–36 months).

Overall, the median preoperative 10-year QRISK2 score was 5.6% (interquartile range 3.3–11.8%). The median postoperative 10-year QRISK2 score in these patients was 4.4% (interquartile range 2.7–9%; p<0.001). The frequency distribution of patients according to procedure, duration of follow-up, and change in QRISK2 score are shown in Table 1.

Table 1.

Frequency Distribution of Patients According to Procedure, Duration of Follow-up, and Change in QRISK2 Score

	Number of patients	Median follow-up (months)	Preoperative QRISK2 score^*	Postoperative QRISK2 score^*	p-Value
LAGB	33	78	7.5 [3.7–10.3]	6.9 [5.7–9]	0.03
LRYGB	50	21	5.1 [3.9–8.2]	3.9 [3.5–5.1]	<0.01
LSG	100	12	5.8 [2.4–14.4]	4.8 [1.5–13.4]	<0.01
BPD	67	60	7.5 [3.5–11.8]	5.9 [2.7–7.4]	0.02
Total	250	24	5.6	4.4	<0.01

Figures expressed are median percentages and [interquartile range]. Statistical significance was calculated at p≤0.05.

LAGB, laparoscopic adjustable gastric banding; LRYGB, laparoscopic Roux-en-Y gastric bypass; LSG, laparoscopic sleeve gastrectomy; BPD, biliopancreatic diversion.

Discussion

The principal finding of this study is that bariatric surgery results in a significant reduction in cardiovascular risk. This study therefore adds to the body of evidence supporting the role of bariatric surgery in improving long-term health outcomes in the morbidly obese population.

Our results have shown a significant quantitative decrease in cardiovascular risk postoperatively in bariatric patients. In addition to this, we have also highlighted that those patients undergoing BPD have a greater risk reduction (1.6%) following surgery when compared to those undergoing LRYGB (1.2%), LSG (1%), or LAGB (0.6%). Overall, we have shown a statistically significant reduction in cardiovascular risk following all types of bariatric surgery in our group (p<0.001). Furthermore, the risk improvement here may be calculated and assessed objectively by both primary and secondary healthcare professionals through QRISK2 scoring. Demonstrating risk reduction through the observation of metabolic syndrome factors is troublesome. A recent systematic review that highlighted a reduction in cardiovascular risk factors in bariatric patients concluded that there remained limitations in cardiovascular risk reporting.⁸

The QRISK2 algorithm was developed with the aim of incorporating all fundamental cardiovascular risk factors into a single scoring system.⁶ It is a more thorough system than its predecessors, and has undergone both validation and comparison studies in recent years, all of which have identified it as being better calibrated to the UK population. It has the added advantage of calculating a 10-year risk figure, thereby going someway to providing a long-term estimation of cardiovascular risk and outcome in our patients.

A potential weakness of our study is that it is observational. We are aware that a prospective randomized trial with a nonsurgical control group would add weight to our findings. However, there are significant and voluminous data showing bariatric surgery to be efficacious in reducing all known obesity-related comorbidities that we did not feel it necessary to have such a comparison group. The data have been extracted from a prospective database, and clearly we have analyzed the data retrospectively. However, as there was no preconceived protocol on how any particular patient was managed or with their follow-up duration, we believe our findings reflect contemporary bariatric surgical practice.

Another possible weakness is the variation in follow-up between the two groups. As with many bariatric units, we have seen a change in our operative practice. We have seen a significant reduction in the rate of BPD procedures performed and have completely abandoned performing the LAGB due to the high incidence of band-related failures.⁹

Conclusions

Our study is the first to use a validated scoring system to assess 10-year cardiovascular risk reduction in patients undergoing bariatric surgery. Our results further support the role of bariatric surgery in reducing cardiovascular risk in these patients and in addition has provided evidence of its long-term benefits.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

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