This analysis of medical insurance claims data shows that (i) short-term mortality as well as long-term mortality after bariatric surgery is significantly higher in men compared to women and (ii) that in patients deceased after bariatric surgery, cardiovascular and psychiatric comorbidities were the most common comorbidities with no sex-specific differences. Moreover, in deceased patients, the incidence of diabetes was higher in men, whereas women suffered more frequently from malignancies. Our results highlight the importance of an individualized, sex-specific preoperative counseling and postoperative follow-up of patients after bariatric surgery.
Several studies demonstrated the favorable outcomes after bariatric surgery including a reduction in overall-mortality [4, 5, 13] reduced hospitalization rates and reduced comorbidities [14]. On the contrary, other observations showed an increased risk of drug- and alcohol-associated mortality [15] and a higher suicide risk after metabolic surgery [16]. However, sex-specific outcomes are not comprehensively analyzed but might be of major importance as the barrier to undergo bariatric surgery is higher in men compared to women, which is reflected by the predominance of females among bariatric surgery candidates [7].
The 30-day mortality and 60-day mortality in our analysis was 0.19% and 0.21%, respectively. This is lower compared to others that reported a 30-day mortality rate of up to 1.1%, depending on the procedure performed [17, 18] and a 60-day mortality rate following bariatric surgery of 0.25% [19]. However, recent studies described a lower 30-day mortality with 0.1% [20]. The 30-day mortality in our analysis over the observation period was stable (range 0.1–0.3%) with almost constantly higher mortality in men compared to women. Sex-specific mortality in men (0.64% per year of observation) was more than two times higher compared to women (0.24%). These results are consistent with the findings from an analysis showing that male sex, higher age, higher body mass index, and psychiatric disorders are linked to higher mortality following bariatric surgery [21].
It was shown that men are more often suffering from comorbidities and have a higher body mass index at the time of the operation compared to women [10]. Also, in our study, the intake of cardiovascular and glucose-lowering medication in the year before the operation was higher in men (Table 2). The higher incidence of diabetes in men observed in this analysis is in line with the literature [10] and of major interest, since it was shown that preoperative diabetes mellitus and hypertension are associated with higher mortality risks in patients with bariatric surgery [19]. However, the overall preoperative intake of antidiabetics and insulin, based on ATC-codes, was 8% and might indicate a low rate of diabetics in this cohort. Nevertheless, this low rate might be an underestimation of the diabetes rate, since only reimbursed drug prescriptions were available. Moreover, the higher age at the operation in men in this analysis is in line with findings from other studies [10, 22] and might also explain the higher postoperative mortality rates in males.
One other potential explanation for the overall better outcomes in women after bariatric surgery might be that the adaptation on protein catabolism occurring during the third trimester of pregnancy [23] might prepare women better for the state of catabolism after bariatric surgery. However, the rate of revision operation in our analysis was significantly higher in women compared to men (3.4 vs. 2.8%, p = 0.04). This finding is in line with the literature showing that revision surgery rates in women are remarkably higher compared to men [8, 24]. Nevertheless, the overall revision rate observed in our analysis was lower compared to other studies [25].
The detailed analysis of all deceased patients with a history of bariatric surgery in this study revealed that cardiovascular comorbidities and psychiatric disorders were the most common findings with no sex-specific differences. This is of special interest since it was shown that depression disorder and coronary heart disease are linked to higher postoperative mortality [21, 26]. Moreover, the increased risk of major depression disorders following bariatric surgery [27] might provide one explanation for the high percentage of psychiatric comorbidities observed in our analysis. Regarding sex-specific disease risk, it was shown that women are more likely to have mental health issues before bariatric surgery, whereas men have higher rates of substance abuse and cardiopulmonary diseases [22]. These findings are in line with the results of our analysis, showing that women more frequently use psychopharmacological drugs before bariatric surgery while usage of cardiovascular drugs, glucose-lowering drugs, and drugs used for treatment of addiction disorders was observed predominantly in men. Moreover, it has been shown that men exerted an unhealthier lifestyle after bariatric surgery including higher alcohol intake and a worse macronutrient intake while exceeding recommended calorie intake [28]. However, in our analysis, malignant diseases were significantly more prevalent in women compared to men. Nevertheless, a meta-analysis demonstrated a favorable effect of bariatric surgery on overall obesity-related cancer rates with greater reduction in women compared to men [29].
The pattern of different bariatric procedures observed in this study cohort is different from the worldwide reported frequencies of metabolic procedures [7], since traditionally gastric bypass is performed more frequently than sleeve gastrectomy in Austria. In addition, a sex-specific difference between the frequency of sleeve gastrectomy and gastric bypass was observed in this analysis. Sleeve gastrectomy was more frequent in men, whereas gastric bypass was performed more often in women. This is of interest, since it was shown that sleeve gastrectomy is more effective in men and gastric bypass is neutral concerning sex-specific outcomes [30]. A meta-analysis demonstrated a higher surgery-associated mortality in observational studies after gastric bypass compared to sleeve gastrectomy [25]. However, this might not explain the different mortality rates in men and women observed in this study, since gastric bypass was more commonly performed in women in the present analysis. Nevertheless, in deceased patients, no sex-specific differences regarding bariatric procedures could be observed in our analysis.
The major limitation of this study is the structure of patient’s data based on medical insurance claims data which only comprises ICD-codes, ATC-codes, and MEL-codes. Detailed information on body mass index, weight reduction or gain, metabolic parameters, and diagnoses from family doctors exceeding drug prescriptions are lacking due to the medical insurance health claims data structure. Moreover, potential coding discrepancies between the medical insurance claims data and the real disease must be considered. Furthermore, no data on suicide was available which might be a relevant information since previous studies reported increased suicide rates after bariatric surgery especially for men, underlying psychiatric disorders, and after gastric bypass surgery [16, 31].
On the other hand, the strength of this analysis is the sample size of nearly 20,000 patients with a history of bariatric surgery. Moreover, medical insurance claims data provide a real-world setting including ICD-diagnoses and MEL-codes from hospitals across the whole country as well as information on drug prescription by ATC-codes outside the hospital. As the medical health insurances in Austria are covering more than 98% of all Austrians, several types of selection biases are excluded.
Taken together, this real-world analysis showed a considerably higher sex-specific mortality in men in the first 30 days after bariatric surgery as well as a higher overall mortality rate in men compared to women. Moreover, in patients deceased after bariatric surgery, cardiovascular and psychiatric comorbidities were frequently observed, with no relevant sex-specific differences. However, diabetes rates were higher in men and malignancies were predominant in women. In conclusion, the higher age at operation in men together with a higher intake of cardiovascular drugs and antidiabetics preoperative highlight the importance of an individualized, sex-specific preoperative counseling before bariatric surgery. Further studies are warranted to evaluate if earlier timing of bariatric surgery in men might improve mortality outcomes.