The registry contained 394,431 individual operation records at the time of last data submission. Numbers of participating countries, national registries, individual centres and submitted cases have steadily increased year on year (Table 2). The number of records submitted ranged greatly from 10 from a single centre to over 80,000 submitted by the Italian national registry (Table 3). We do not have complete country-data on case ascertainment.
The majority of the database records fell in the period 2009–2018 (88.5% of the total) although some countries have submitted data from procedures prior to 2000; 190,177 of primary operations were dated in the calendar years 2014–2018. Forty-six percent of the baseline records were > 80% complete in data submitted in the calendar years 2014–2018. Variation in data completion for the whole registry is presented (Table 4).
The following baseline analyses relate to primary operations in the calendar years 2014–2018. The overall proportion of female patients was 73.7% (95% CI: 73.5–73.9%). Although operations were more common in females in all countries, there was also a wide variation in the gender ratios, ranging from 50.9% female in Georgia (55/108) to 93.4% female in Guadeloupe (183/196). For the 16 countries with ≥ 1000 submitted patients, the gender ratios were 57.7% female (India; n = 11,088) to 79.4% female (Netherlands; n = 37,818).
The median BMI pre-surgery was 41.7 kg m2 (inter-quartile range: 38.3–46.1 kg m2); there was a wide variation between different contributor countries, with medians ranging from 34.2 kg m2 in South Korea to 49.1 kg m2 in Germany (Fig. 1a). The median age at time of operation was 42 years (inter-quartile range: 33–51 years; Fig. 1b) There was variation between countries with a trend to Middle Eastern and Asian countries having a younger, or adolescent practice, with those in the West more commonly operating at an older age. For the 16 countries with ≥ 1000 submitted patients, the BMI range was 37.3 (China; n = 1939) to 44.5 (Saudi Arabia; n = 2119).
Obesity-Related Disease Prior to Surgery
As expected, a large proportion of patients had obesity-related disease. There was large variation in the reported rates of these conditions between countries. Overall, those on medication for type 2 diabetes made up 19.8% of patients (inter-country variation: 4.5–97.7%); 30.6% were treated for hypertension (10.9–92.6%) and 12.4% of patients were on medication for depression (0.0–54.4%). Also, 24.3% of patients reported requiring treatment for musculoskeletal pain (0.0–65.1%); 18.6% of patients had diagnosed sleep apnea (0.0–74.3%); and 17.0% of patients had gastro-esophageal reflux disease (0.0–54.8%). Amongst those countries with ≥ 1000 submitted patients, the respective figures were 19.5% (9.8–43.5%) for type 2 diabetes, 30.2% (15.5–46.3%) for hypertension, 12.5% (0.6–29.1%) for depression, 24.6% (0.0–50.4%) for musculoskeletal pain, 18.4% (0.0–36.8%) for sleep apnea and 17.0% (6.4–40.7%) for GERD. The variation in disease prevalence between regions is shown (Fig. 2a, b).
Stratification for Operative Risk
An estimate of operative risk as determined by the Obesity Surgery Mortality Risk Score (OSMRS) varied widely by country (Fig. 3) . Georgia, Bulgaria and Hong Kong had the highest risk patient populations (OSMRS groups B and C: 78.7%, 72.2% and 66.7%, respectively); South Korea, Bolivia and Kuwait show the least risk (OSMRS groups B and C: 12.5%, 20.5% and 22.2%).
Almost all, 99.3%, operations were performed laparoscopically. In the time period of this analysis, there were 72,645 Roux en Y gastric bypass operations (38.2%), 87,467 sleeve gastrectomy operations (46.0%), 14,516 one anastomosis gastric bypass procedures (7.6%) and 9534 gastric banding operations (5.0%). Although in the whole registry Roux en Y gastric bypass is the most recorded operation, in the last 2years, the number of sleeve gastrectomies recorded is greater than the number of Roux en Y gastric bypasses.
Mexico (205/253, 81.0%), Colombia (282/356, 79.2%) and Brazil (595/808, 73.6%) reported the highest proportions of gastric bypass surgery; Australia (284/284, 100.0%), Saudi Arabia (2122/2122, 100.0%) and Guadeloupe (196/197, 99.5%) reported the highest rates of sleeve gastrectomy operations. Those figures may represent local, rather than national practice since, of these countries, only Brazil submitted data from a national registry. Region variation in operation type is displayed in Fig. 4 and Table 5.
Length of Stay
The vast majority of patients who had a gastric band inserted were discharged within 1 day of their operation (88.5%); gastric bypass patients within 2 days of surgery (84.1%); and sleeve gastrectomy patients within 3 days (84.5%). This variation in trends was marked between different regions with the shortest lengths of stay being in North America (single-centre data; Fig. 5).
One-Year Follow Up
For the 184,871 primary operations recorded between 2012 and 2016, 116,431 had follow-up records (63.0%). One-year follow-up was more complete in those patients having Roux en Y gastric bypass than sleeve gastrectomy (57.4% vs 29.4%). Variation in attainment of follow-up data for the Roux en Y gastric bypass group is shown (Table 6).
Over all types of surgery, the average recorded percentage weight loss was 28.9% a year after surgery: 30.0% for Roux en Y; 29.1% for gastric sleeve; 16.1% for gastric band; and 32.9% for one anastomosis gastric bypass. As would be expected, the percentage weight loss at 1 year was greater in those with a higher initial BMI (Fig. 6a).
One year after primary surgery, 66.1% of those taking medication for type 2 diabetes beforehand were no longer on medication; the proportion of patients no longer treated for diabetes was highly dependent on weight loss achieved, with the rate of improvement increasing with higher percentage weight loss (Fig. 6b).