Morbidity and mortality after bariatric surgery in Sweden

Abstract

Overweight and obesity has increased in Sweden and in the rest of the world during the last decades, probably due to a more sedentary lifestyle and changes in diets. Body mass index (BMI) is a commonly used index of weight-for-height for classifying adult individuals. BMI is weight in kilograms divided by the square of the height in meters (kg/m²). BMI between 18.5 and 25 is called normal weight. Overweight is defined as a BMI over 25 and obesity as BMI over 30. A BMI over 40 is sometimes referred to as morbid obesity.

Obesity is associated with several diseases such as diabetes type 2, hypertension, obstructive sleep apnea and different cancers. Obesity is also associated with an increased risk of preterm mortality. Intentional weight-loss, by any mean, may lead to resolution of the obesity related diseases and to a reduction in mortality risk. Weight-loss can be achieved by modification of life-style factors, diets, pharmacological treatment or surgery. For morbidly obese people surgical treatment is the most effective method to attain sustainable weight reduction. For this reason surgery has become increasingly popular with increasing number of operations being performed annually.

The overall objective of the studies comprising this thesis work was to investigate morbidity and mortality after weight-loss (bariatric) surgery. Specific aims were to: 1) study long-term outcome after laparoscopic vertical banded gastroplasty with regards to weight-loss and long-term postoperative complications; 2) study short- and longterm mortality after bariatric surgery; 3) study if bariatric surgery could lower mortality in an obese group of men compared to an obese group of non-operated men; and, 4) to study morbidity- and mortality rates after the most common bariatric procedure in Sweden today, the gastric bypass. This thesis work is based on data from one quality registry held at Danderyd Hospital and on nationwide data sets created by record linkage between the Swedish inpatient care registry, the registry of the total population and other national registries.

This thesis covers the time period 1980 to 2006. During these years there has been an increase in bariatric procedures with the most rapid increase seen during the last 5 years. Throughout the time-period early postoperative mortality in Sweden has been low, comparable to expert centers in the United States. Mortality within the first year after surgery was found to be higher among men raising the question whether any longterm gains in survival advantage attained through the weight-loss surgery would be wiped out by the increased early mortality. However, when comparing mortality between a cohort of surgically treated obese men and a cohort of obese non-operated men a survival advantage was seen in the surgical cohort. During years covered by the datasets used in this thesis work there has been a shift towards more complex procedures. Vertical banded gastroplasty is a restrictive procedure that was popular in the 1990:es and later on reintroduced with a laparoscopic approach.

The long-term result regarding weight-loss was modest and rates of surgical reinterventions, either due to complications or insufficient weight-loss was high. With a failed vertical banded gastroplasty conversion to a gastric bypass gave the best results. Gastric bypass is the predominant procedure in Sweden today mostly conducted by a laparoscopic approach. The laparoscopic approach is considered technically more challenging than the open approach, which has raised concerns whether complication rates would be higher after laparoscopic surgery. There was no difference in mortality between the two approaches and no major differences regarding postoperative morbidity. However, much higher complication rates were noted after revisional procedures, when a previous bariatric procedure was converted to a gastric bypass.

In summary, bariatric surgery can be performed safely on a national level. Men have a survival advantage after bariatric surgery compared to obese non-operated men yet it remains elevated compared to the general population. High revisional rates were seen after laparoscopic vertical banded gastroplasty. Laparoscopic gastric bypass is as safe as open gastric bypass; however revisional procedures, by any approach, have much higher complication rates. Therefore, it is important to make an evidence-based choice when bariatric surgery is conducted for the first time.