Roux-en-Y gastric bypass (RYGB) seems to be associated with a decreased risk of myocardial infarction, according to a study by researchers from Sweden. However, the procedure does not appear to decrease the risk of ischaemic stroke within ten years of follow-up. The findings were featured in the paper, ‘Risk of Myocardial Infarction, Ischemic Stroke, and Mortality in Patients Who Undergo Gastric Bypass for Obesity Compared With Nonoperated Obese Patients and Population Controls’, published in the Annals of Surgery.
“This study found that obese patients who had undergone RYGB had lower ten-year risk of myocardial infarction than non-operated obese patients and similar risk to that of non-obese population controls; however, they had similar ten-year risk of ischemic stroke as non-operated controls,” the investigators reported. “The results also indicated that RYGB reduced short-term, but not long term, cardiovascular-related and all-cause mortality compared with non-operated obese, and that patients who underwent RYGB had an excess risk of mortality compared with nonobese population controls.”
The authors stated that previous studies have highlighted the decreased risk of cardiovascular-related morbidity and mortality compared with medical treatment, in particular among patients with obesity and type 2 diabetes. Nevertheless, there is a lack of studies on the risk of fatal and nonfatal myocardial infarction and ischemic stroke as separate events due to limited number of participants.. The authors designed a study to estimate risk of myocardial infarction, ischemic stroke and cardiovascular-related and all-cause mortality after RYGB, compared with both non-operated patients with obesity and matched nonobese population controls.
Using data from the Swedish National Patient Registry, they included all individuals 20 to 65 years of age who obtained a first recorded principal diagnosis of obesity (ICD-10 codes E65 or E66) in the Patient Registry between January 2001 and December 2013. For patient with obesity, two control participants, matched by year of birth, sex, and area of residence, and without a code representing obesity diagnosis or bariatric surgery, were randomly selected from Sweden’s Registry of the Total Population using the individual personal identity number assigned to all Swedish residents.
Patients with obesity were divided into two groups, one RYGB group and one group including non-operated obese patients. Through this procedure, they captured 81% of all individuals who underwent RYGB in Sweden during the study period. Outcomes were obtained from the Patient Registry and the Cause of Death Registry according to the ICD-10. Disorders present before or at the study baseline (two years after obesity diagnosis) included the following diagnoses: obesity, myocardial infarction, ischemic stroke, diabetes, hypertension, sleep apnoea, coronary heart disease and malignancy.
Outcomes
The study included 28,204 patients who underwent RYGB (90.3% laparoscopic surgery), mean age 40.8 years [standard deviation (SD) 10.4] with 75.5% women and 55,903 matched non-obese population controls, as well as 40,827 non-operated obese patients, mean age 43.1 years (SD 11.8) with 68.5% women and 80,800 matched nonobese population controls. The majority of patients (>90%), irrespective of whether they later underwent surgery or not, were registered in an outpatient setting. The prevalence of obesity-related comorbidity was fairly similar among RYGB and non-operated obese patients, where diabetes (14.7% and 16.2%, respectively) and hypertension (23.9% and 23.4%, respectively) were the most common comorbidities. The prevalence of comorbidity among the non-obese population controls was low, the most common comorbidities were malignancy (3.1%– 3.8%) and hypertension (3.3%–4.2%).
Compared with non-operated obese patients, RYGB patients had a reduced short- and long-term risk of myocardial infarction with HR (95% CI) of 0.44 (0.28–0.68) and 0.60 (0.41–0.88) respectively. In a sensitivity analysis, the model was further adjusted for pre-existing coronary heart disease, and the results were similar to those of the main analysis.
For ischemic stroke, no clear short- but a borderline significant long-term difference were found: HR 95% CI of 0.79 (0.54–1.14) and 0.68 (0.48–0.96). RYGB patients had a decreased risk of cardiovascular-related and all-cause mortality compared with non-operated obese patients within the first three years of follow-up: HR (95% CI) of 0.47 (0.35–0.65) and 0.66 (0.54–0.81), respectively. However, this reduced risk was attenuated and no longer statistically significant during the final three to ten years of follow-up, with HR (95% CI) of 0.78 (0.60–1.01) and 0.94 (0.78–1.13), respectively.
Compared with non-obese population controls, RYGB patients had an increased long-term risk of ischemic stroke (HR = 1.61,95% CI 1.13–2.31), cardiovascular-related mortality (HR = 2.43, 95% CI = 1.84–3.20) and all-cause mortality (HR = 1.91, 95% CI 1.59–2.30). However, both short- (HR = 0.67, 95% C 0.44–1.04) and long-term (HR = 1.02, 95% CI 0.72–1.46) risk of myocardial infarction was similar to that of non-obese population controls. An increased short-and long-term risk of all outcomes was found among non-operated obese patients compared with nonobese population controls.
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