Health-care costs over 15 years after bariatric surgery for patients with different baseline glucose status: results from the Swedish Obese Subjects study

Abstract

Background: Bariatric surgery prevents and induces remission of type 2 diabetes in many patients. The effect of preoperative glucose status on long-term health-care costs is unknown. We aimed to assess health-care costs over 15 years for patients with obesity treated conventionally or with bariatric surgery and who had either euglycaemia, prediabetes, or type 2 diabetes before intervention.

Methods: The Swedish Obese Subjects (SOS) study is a prospective study of adults who had bariatric surgery and contemporaneously matched controls who were treated conventionally (age 37-60 years; BMI of ≥34 in men and ≥38 in women) recruited from 25 Swedish surgical departments and 480 primary health-care centres. Exclusion criteria were identical for both study groups, and were previous gastric or bariatric surgery, recent malignancy or myocardial infarction, selected psychiatric disorders, and other contraindicating disorders to bariatric surgery. Conventional treatment ranged from no treatment to lifestyle intervention and behaviour modification. In this study, we retrieved prescription drug costs for the patients in the SOS study via questionnaires and the nationwide Swedish Prescribed Drug Register. We retrieved data for inpatient and outpatient visits from the Swedish National Patient Register. We followed up the sample linked to register data for up to 15 years. We adjusted mean differences for baseline characteristics. Analyses were by intention to treat. The SOS study is registered with ClinicalTrials.gov, number NCT01479452.

Findings: Between Sept 1, 1987, and Jan 31, 2001, 2010 adults who had bariatric surgery and 2037 who were treated conventionally were enrolled into the SOS study. In this study, we followed up 4030 patients (2836 who were euglycaemic; 591 who had prediabetes; 603 who had diabetes). Drug costs did not differ between the surgery and conventional treatment groups in the euglycaemic subgroup (surgery US$10,511 vs conventional treatment $10,680; adjusted mean difference -$225 [95% CI -2080 to 1631]; p=0·812), but were lower in the surgery group in the prediabetes ($10,194 vs $13,186; -$3329 [-5722 to -937]; p=0·007) and diabetes ($14,346 vs $19,511; -$5487 [-7925 to -3049]; p<0·0001) subgroups than in the conventional treatment group. Compared with the conventional treatment group, we noted greater inpatient costs in the surgery group for the euglycaemic ($51,225 vs $25,313; $22,931 [19,001-26,861]; p<0·0001), prediabetes ($58,699 vs $32,861; $27,152 [18,736-35,568]; p<0·0001), and diabetes ($61,569 vs $47,569; 18,697 [9992-27,402]; p<0·0001) subgroups. We noted no differences in outpatient costs. Total health-care costs were higher in the surgery group in the euglycaemic ($71,059 vs $45,542; $22,390 [17,358-27,423]; p<0·0001) and prediabetes ($78,151 vs $54,864; $26,292 [16,738-35,845]; p<0·0001) subgroups than in the conventional treatment group, whereas we detected no difference between treatment groups in patients with diabetes ($88,572 vs $79,967; $9081 [-1419 to 19,581]; p=0·090).

Interpretation: Total health-care costs were higher for patients with euglycaemia or prediabetes in the surgery group than in the conventional treatment group, but we detected no difference between the surgery and conventional treatment groups for patients with diabetes. Long-term health-care cost results support prioritisation of patients with obesity and type 2 diabetes for bariatric surgery.

Funding: AFA Försäkring and Swedish Scientific Research Council.

Copyright © 2015 Elsevier Ltd. All rights reserved.

Figures

Figure 1. Aggregated 15-year healthcare costs

Mean differences adjusted for baseline age, sex, smoking, body mass index, inclusion period (≥ 1995), drug costs and hospital costs the year prior to the index date. Hospital days and costs were retrieved from the National Patient Register between 1987 and 2013, and data were not imputed (apart from missing cost data which were calculated from the observed number of hospital days). Outpatient care data were retrieved from the National Patient Register between 2001 and 2013 for observation years 2 to 15, with multiple imputation used for missing data. Drug cost data were retrieved from the Prescribed Drug Register between 2005 and 2013, and from self-reported drug use in SOS (years 1, 2, 3, 4, 6, 8, 10, 15), with multiple imputation used for missing data. *Total (sensitivity): Sensitivity analysis where the length of stay for the index bariatric surgery reflected practice in Sweden in 2012. Costs are reported in 2013 US$.

Figure 2. Mean Annual Prescription Drug Costs from Year 0 to 15 (Years 0–6: Questionnaire data; Years 7–15: Register data from the Prescribed Drug Register, data capture 2005–2013)

Adjusted for baseline age, sex, smoking, body mass index and inclusion period (≥ 1995), and drug costs the year prior to the index date (year 0). Error bars indicate 95%CIs derived by nonparametric bootstrapping. Data were not collected in year 5 and therefore no data are presented. Results are based on observed data. Imputed vs observed data are shown in eFigure 2. *Self-reported drug data collected for follow-up years 0–6 (left) and Swedish Prescribed Drug Register data for follow-up years 7–15 (2005–2013) (right). Costs are reported in 2013 US$.

Figure 3. Mean Annual Diabetes Drug Costs from Year 0 to 15 (Years 0–6: Questionnaire data; Years 7–15: Register data from the Prescribed Drug Register, data capture 2005–2013)

Adjusted for baseline age, sex, smoking, body mass index and inclusion period (> 1995), and diabetes drug costs the year prior to the index date (year 0). Error bars indicate 95%CIs derived by nonparametric bootstrapping. Data were not collected in year 5 and therefore no data are presented. Results are based on observed data. Imputed vs observed data are shown in eFigure 2. Drugs presented are those included in ATC group “A10 – Drugs used in Diabetes”. *Self-reported drug data collected for follow-up years 0–6 (left) and Swedish Prescribed Drug Register data for follow-up years 7–15 (2005–2013; right). Costs are reported in 2013 US$.

Figure 4. Mean Annual Hospital Costs from Years 1–15 (From the National Patient Register, data capture 1987–2013)

Adjusted for baseline age, sex, smoking, body mass index and inclusion period (≥ 1995) and hospital days in the year prior to the index date. Error bars indicate 95%CIs derived by nonparametric bootstrapping. Results are based on observed data.

Figure 5. Mean Annual Outpatient Care Costs from Years 2 to 15 (From the National Patient Register, data capture 2001–2013)

Adjusted for baseline age, sex, smoking, body mass index and inclusion period (≥ 1995). Error bars indicate 95%CIs derived by nonparametric bootstrapping. Results are based on observed data. Imputed vs observed data are shown in eFigure 1.