Forty-six of 61 countries that contributed data to the Global Registry 2015–2018 had completion rates of ≥90% for baseline T2DM status, and 26 countries submitted ≥1000 records. Fifteen countries met the inclusion criteria and had data available for further analysis, including 11 of the 14 contributing national registries, comprising 69.5% (413,048) of the 594,235 operation records for the date range (2015–2018) of the 5th IFSO report. The mean baseline T2DM data completion rate was 99.6% (country range 93.7–100%). The number on medication for T2DM was 99,537 of 411,581 (24.2%, country range 12.0–55.1%) and 77.1% of the overall population was female. The total numbers of operations, numbers per country with T2DM, rates of female patients and BMI are shown (Tables 1 and 2). No sex data were available for Chile. OAGB was not separately identified in the USA during the study period.
Demographic Characteristics of Those with and Without T2DM
In every country, patients with T2DM were older than those without T2DM (overall mean age 49.2 (11.4) years vs 41.8 (11.9) years, all p < 0.001) (Table 2). Men were older than women irrespective of T2DM status. The mean ages of men and women with T2DM were 50.9 (11.1) years and 48.5 (11.5) years respectively, p < 0.001, and for those without T2DM 42.3 (12.1) years and 41.8 (11.8) years respectively, p < 0.001.
The overall BMI was slightly higher for those with T2DM (mean 46.9 (8.7) kg/m2 vs 46.2 (8.1) kg/m2, p < 0.001). However, the BMI was higher in only 4 countries including the USA, the biggest contributor to the dataset, lower in 4 countries, and similar in 7 countries (Table 2). The majority of all patients with T2DM were in the BMI range 40.0–49.9 kg/m2, despite the older age of those with T2DM.
The proportions of operated patients with T2DM varied widely from country to country. Sweden (12.0%) and France (12.3%) had the lowest, and Austria (55.1%) had the highest proportion of patients with T2DM (Fig. 1, Supplementary file Table 1).
The proportions of patients with T2DM in each obesity class are shown (Fig. 1, Supplementary file Table 1). A larger proportion of men were represented in the lower BMI classes, OR for BMI <35 kg/m2 compared to ≥35.0 kg/m2 2.76 (2.52–3.03), p < 0.001 (Supplementary file Tables 2, 3). For women the equivalent OR was less than 1 with higher rates of T2DM in higher BMI ranges, OR 0.78 (0.73–0.83), p < 0.001. The USA contributed 72% of the patients, and when the remaining 28% of patients were analysed separately, the trends still remained for men, OR 2.47 (2.22–2.75), and for women, OR 0.85 (0.78–0.92), both p < 0.001.)
In 9 of 14 countries there were proportionately more men with T2DM compared to women with T2DM (p < 0.001). In Bahrain, Egypt, Kuwait Qatar, and UAE proportions were similar (Table 1). Overall, men had 68% greater odds for having T2DM compared to women (32%/21.9%, OR 1.68 (1.65–1.71), p < 0.001, Supplementary file Tables 2, 3). This pattern was not altered by excluding the USA data, OR 1.91 (1.85–1.97), p < 0.001).
Proportions of Operated Patients with T2DM Compared to Country T2DM Prevalence
The proportion of operated male and female patients with T2DM for each country is shown compared to the individual country prevalence of T2DM (adults age ≥ 18 years) (Fig. 2, Supplementary file Table 4). Countries have been ordered by an increased prevalence of T2DM and a prevalence line indicated in Fig. 2. For Austria the proportion of patients with T2DM choosing surgery was well above the national prevalence rate for both sexes: 60.5% (56.6–64.4%) men had T2DM, 53.6% (51.1–56.1%) women had T2DM. In contrast for 2 countries, the proportions choosing surgery were below the prevalence rates for men, and for 3 countries, they were below the prevalence rates for women.
Procedure Performed Based on T2DM Status
Together, RYGB, OAGB and SG comprised 94.4% of total procedures for those without T2DM and 95.3% for those with T2DM (Supplementary file Table 5). For those without T2DM the individual operations comprised RYGB 25.1%, OAGB 3.4% and SG 65.8%. For those with T2DM the individual operations comprised RYGB 36.4%, OAGB 4.0% and SG 54.9%, OR 0.63 (0.63–0.64), p < 0.001 for SG vs non-SG for patients with T2DM. Twelve of 15 countries had higher proportions of gastric bypass (RYGB or OAGB) compared to SG operations for patients with T2DM compared to those without T2DM (Fig. 3/Supplementary file Table 5), OR 1.70 (1.67–1.72), p < 0.001. The equivalent OR with USA data excluded was 1.94 (1.88–2.00), p < 0.001. There were no significant differences for Austria, Kuwait or Qatar.