To our knowledge, this is the longest follow-up study peformed to investigate mortality in LAGB as opposed to medical treatment. We found that after a follow-up period of up to 17 years (mean 13.9 ± 1.87 years), diabetic and nondiabetic patients undergoing LAGB died less frequently than control patients, and experienced a lower number of new diseases, in particular CV diseases and diabetes, as indicated by exemptions for chronic diseases and hospital admissions. Death counts were similarly lower, for both diabetic and nondiabetic patients, with surgey than in controls; in contrast, for exemptions, when considering diabetic and nondiabetic patients separately, a significant benefit (surgery vs no-surgery), appeared only for the latter.
Reduced mortality applied to both CV mortality and to all-cause mortality, in particular to neoplasia-induced mortality; other causes of death were too few to make any comparison meaningful. Reduction of mortality was similar in diabetic and nondiabetic patients, as already reported in the SOS study with a shorter follow-up period, in a cohort in which diabetic patients accounted for only 10 % [13, 20]. The benefit shown in this study (HR 0.35, 95 % CI 0.19–0.65 at univariate analysis; HR 0.41, 95 % CI 0.22–0.76 at multivariate analysis) was similar to the average benefit observed in shorter studies (meta-analysis) [18], and to previous studies in which LAGB was used [14, 17]. In addition, the benefit appeared for patients aged ≥42 years, as suggested by previous studies [14, 16, 17, 20]. This is likely due to the low mortality rate of younger patients; for instance, in the SOS study, patients under the age of 37 years were excluded to ensure high overall mortality [13]. Similar to SOS study [39], we also found a significant reduction of neoplasia, only in neoplasia-induced mortality, not in neoplasia-induced hospital admissions or exemptions.
This study has strengths and limitations. This was not a purely administrative study, as we identified obese patients seeking medical advice at the four Institutions; both diabetic and nondiabetic patients were from the same cohort, asking for medical advice, and either undergoing medical treatment or surgery; therefore, we dealt with patients that were not simply obese. At the same time, dealing with outpatients, we avoided the possible bias of patients hospitalized for serious diseases; this, in our opinion, is representative of obese patients. Looking at medical baseline records together with administrative records offers a greater number of variables (anthropometric and clinical data, biochemistry) than using administrative records alone.
In addition, this is the longest follow-up study performed so far, with no patient lost to follow up; the low number of patients observed after a mean period of almost 14 years simply depends on the late beginning of treatment, surgical or medical, and a longer follow-up period will make these numbers greater. Also, the results were obtained after matching patients for age, sex ratio, BMI, systolic and diastolic blood pressure. A similar matching has been used in similar, albeit shorter-duration studies [13, 20, 22], while in other studies matching had been done only for age, sex, and BMI [11, 12, 14, 15]. Since this is an ongoing study, a further 5 years follow-up study will answer many of the as yet unresolved questions.
The limitations lie in the relatively small number of patients. Second, this study was carried out in Institutions that offered medical or surgical treatment with the indications/contra-indications of that era; for instance, randomization of patients to surgery or to medical treatment was deemed unethical. Third, even though weight loss has not been routinely reported in previous studies [18], weight loss could be retrieved only in a small group of patients after a mean period of 12 years; a small but clear difference was found, similar to previous studies of shorter duration [13, 14]. Fourth, this was an analysis based on initial inclusion of patients in a group, and therefore we did not consider LAGB removal, occurring in 54 patients; no patient underwent new bariatric procedures. The fifth limitation is that of possible under-reporting of exemptions from medical expenses, but one should consider that exemptions are of significant monetary advantage for patients. We can assume that patients undergoing surgery were more concerned about their health conditions, and we can assume that if any, they were more likely to ask for exemptions than controls; this would lead to over-reporting for surgery than for no-surgery patients, and therefore for more exemptions among surgery than no-surgery patients, contrary to actual figures.
A final word of caution lies in the use of medical records: medical records were considered only at baseline, not later, even because of the high rate of loss to follow-up commonly observed in obese patients. This can lead to non-consideration of possible risk factors for mortality during the following period; for instance, atrial fibrillation [40] and high heart rate [41, 42] are common in obesity and in diabetes, and are both risk factors for mortality; even though atrial fibrillation was present in very few patients at baseline, we can not exclude that atrial fibrillation can have appeared later in our patients; on the other side, baseline heart rate did not affect mortality (being somewhat higher in surgery than in no-surgery patients). Also, baseline HbA1c did not affect mortality, but we do not know how HbA1c changed during the following years.
Benefits of bariatric surgery are probably more than simply related to improved metabolic control; improvement of metabolic control with resolution of diabetes can last several years [43], but diabetes can re-appear after resolution, while other effects (lipid metabolism, kidney function, systolic and diastolic blood pressure) can be maintained for longer periods, being instrumental in the better overall prognosis [44]. A few, mostly uncontrolled, studies have shown additional effects: improved endothelial function, decrease of intima-media-thickness (IMT), reduction of insulin resistance, decrease in vascular and general inflammation, increase of HDL cholesterol, decreased sympathetic activity, decreased left ventricular hypertrophy; these effects have recently been reviewed [45], and might explain the effects of bariatric surgery on cardiovascular disease. We found that a small weight loss persists years after LAGB, and might be one of the reasons for decreased mortality [44], together with reduced incidence of diabetes and CVD; also, the number of patients with arterial hypertension (with or without organ damage, Table 4, ICD I10-I15), was different at the end, and can be of clinical relevance.
Finally, we should remember that at present data about reduced long-term mortality after bariatric surgery are available only for LAGB and RYGB, while there is no information available for sleeve gastrectomy, biliopancreatic diversion, and biliointestinal bypass, three types of very effective surgery.
In conclusion, these data show that LAGB is associated with lower mortality up to 17 years in diabetic and nondiabetic obese patients, and with fewer new cases of diabetes and of CV disease. A new examination is planned for September 2017. If the above assumptions are correct, we expect an even greater preventive effect of LAGB in diabetic and nondiabetic patients with morbid obesity. The fact that benefits were similar in diabetic and nondiabetic patients is of clinical relevance; diabetologists should inform their patients of the potential benefits of bariatric surgery, not only the possible remission of diabetes [23], but also the protective role against excess mortality.