Bariatric surgery: predictors of outcome : results from a national database (SOREG) with particular emphasis on patients’ age

Sammanfattning: A global pandemic of obesity and its health-related concerns, in form of comorbidities, increased risk of mortality, and reduced health-related quality of life, is ongoing. At the same time, conservative treatment for obesity, including life-style changes (mainly diet regimens and physical activity), is most often associated with unsatisfactory long-term results, and the most effective treatment for obesity itself as well as obesity-related health problems is surgery (1-3). Due to the increase in obesity, a simultaneously rise in bariatric procedures has occurred. Further, due to a worldwide increasing age, as well as rise in age-related obesity, bariatric procedures in patients over 60 years has also increased. Thus, between 1999 and 2005 older patients (≥60 years) accounted for 2,7% of the total number of procedures, compared to almost 10% during the period 2009-2013 (4). The safety and outcome of bariatric surgery for elderly has been debated, while benefits of preoperative weight loss before surgery is more consolidated (5-7). In conclusion, the aim of this thesis was to evaluate the effects of bariatric surgery in relation to preoperative weight loss and outcome in the elderly. In the first (I) paper, the correlation between preoperative weight loss and preoperative body mass index (BMI) in relation to postoperative weight loss was analysed. We used a cohort of 9,570 patients in a complete data set. A preoperative weight loss in the 25th, 50th, and 75th percentile of 0%, 4.5%, and 8.6% was seen, respectively. Patients in the 50th percentile were compared for preoperative weight loss with reference (25th percentile), with a postoperative weight loss 5.0 and 5.3% higher at one and two years, respectively (p<0.001). Corresponding values for patients in the 75th percentile were 11.8% and 10.1 % (p<0.001). A more pronounced effect on patients in the 75th percentile of preoperative BMI (>45.7 kg/m2) was seen, with a 15.2% and 13.6% higher total weight reduction after one and two years compared to the reference (25th percentile) for preoperative weight loss. The risk for complications and mortality in relation to age after gastric bypass was evaluated in the second (II) paper (n = 47 600). In the entire cohort, the 30-days follow-up rate was 98.1% with a risk of any complication at 8.4%, whereas patients in the age-groups 50-54 years, 55-59 years and ≥ 60 years, had a significantly increased risk at 9.8%, 10.0%, and 10.2%, respectively, for any complication. In a multivariate analysis, the risk of major surgical complications such, as anastomotic leak, bleeding, and deep infections/abscesses, were all increased significantly by 14-41% for patients aged 50-54, years with a small but not significantly increased risk for those of an older age. The risk of medical complications (thromboembolic, cardiovascular, and pulmonary complications) was significantly higher for patients ≥ 60 years with, a total mortality of 0.03%. In the third (III) paper, the resolution of obesity-related comorbidities (type 2 diabetes, hypertension, dyslipidaemia, OSAS, and depression) after gastric bypass in relation to age over time (at one, two and five years, postoperatively) was evaluated (n=57,215). Resolution was defined as no longer in need of pharmacological (or CPAP) treatment. The follow-up rates for eligible patients were 89%, 69%, and 59 % at one, two, and five years, respectively, and 64 % in patients for those older than 60 at five years. The prevalence of most comorbidities at baseline was higher in patients over 60 years, compared to younger ones. For those 60 and above, a relative improvement compared to preoperative prevalence for diabetes, hypertension, dyslipidaemia, and OSAS of 45%, 10%, 24, and 62%, respectively, was seen at five years. In the fourth (IV) paper, health-related quality of life (SF-36 and OP) was evaluated at one, two and five years after gastric bypass, and the same cohort as in paper III was used. Further, in all age groups, the mental aspects of QoL (MCS) returns nearly to baseline after five years, compared to PCS and OP, with a maintained improvement up to five years after surgery. In conclusion, patients over 60 had an improvement in parity with younger individuals with regard to MCS, PCS and OP. In summary, an association was found between a preoperative low caloric diet and a subsequent weight loss before surgery, and a better maintained weight loss up to two years after surgery. This is particularly evident for those with the highest levels of BMI. Gastric bypass in the elderly (≥ 60 years) exhibits an increased, but acceptable, risk for complications and mortality compared to younger patients. Further, the elderly have good resolutions, although not in the same range as younger patients, of obesity-related comorbidities, and good effects on health-related quality of life, comparable to younger individuals, up to five years after gastric bypass. Taken together, these result support that a preoperative weight loss, in line with the association to a reduced risk of complications, entails a better maintained weight loss as well. Furthermore, elderly have a good effect on obesity-related comorbidity and health-related quality of life, with acceptable but increased surgical risk.