National health and economic impact of a lifestyle program to prevent type 2 diabetes mellitus in Germany: a simulation study

Introduction

Results from clinical trials and translation studies in real-world settings show that type 2 diabetes can be prevented or delayed by lifestyle interventions in individuals with increased risk of type 2 diabetes.1 Those lifestyle interventions were also found to be cost-effective or even cost saving2 from a healthcare system perspective in many countries. A recent systematic review of trial-based studies demonstrated that various interventions to prevent type 2 diabetes in high-risk populations were both cost-effective and feasible in diverse settings.3 The gap between gold-standard results shown in trials and effectiveness in everyday practice is usually addressed in pragmatic studies designed to be practical and applicable in real-world clinical settings. Such pragmatic lifestyle programs have been successfully established in the routine practice in some Western countries4–7 and there is robust real-world evidence that these programs are effective in lowering weight and hemoglobin A1c (HbA1c) if implemented in practice.8 The systematic review on the effectiveness of pragmatic lifestyle interventions for preventing type 2 diabetes found that these interventions led to weight loss, and adherence to guidelines was significantly associated with greater weight loss.9 A quasi-experimental evaluation of a nationwide diabetes prevention program, utilizing electronic health records from over 2 million patients, provided causal evidence of improved glycemic control and reduced risk factors in the behavior change program for pre-diabetes.8 A systematic review found that lifestyle interventions targeting high-risk individuals were generally cost-effective for preventing type 2 diabetes from a healthcare system or societal perspective.2

In the USA, the National Diabetes Prevention Program (US-NDPP) was authorized by the US Congress in 2010 and since then has been delivered by over 1500 organizations, reaching almost 300 000 people.4 The British National Institute for Health and Care Excellence (NICE) recommends a lifestyle intervention for individuals with intermediate categories of hyperglycemia for preventing type 2 diabetes,5 6 and the National Health Service (NHS) England launched the NDPP (NHS-NDPP) in 20166 10 into significant health benefits for participants.8 In Germany, several programs have been recommended.11 However, to date, no such program was put into action.

Whether a national program like those in the USA and the UK would be a good use of healthcare resources in Germany is unknown. Evidence from the USA or the UK may not be directly applicable to Germany due to two main reasons. First, the population characteristics of people at high risk of developing type 2 diabetes might differ. Second, the costs for treating diabetes and its complications are highly context-specific and country-specific. In German setting, the lifestyle programs of diabetes prevention were evaluated in a handful of studies.12–15 These studies either overlooked diabetes complications12 13 or primarily focused on weight management, without directly estimating the impact of lifestyle interventions on diabetes incidence.14 15 Furthermore, previous studies often ignored productivity losses and evaluated those programs from a narrow healthcare system perspective and did not consider potential heterogeneity in the cost-effectiveness across the age range.2 Without that, both the societal value of these programs as well as the target populations with the most favorable cost-effectiveness ratio remain unknown.

In this study, we aim to examine the long-term health and economic impact of a pragmatic lifestyle program, as successfully implemented in large scale in other countries, for Germany from a healthcare payer and societal perspective. We also examine how the effectiveness and cost-effectiveness of the lifestyle program to prevent type 2 diabetes vary by age group at both individual and population levels.

Methods and materials

Results

Cost-effectiveness of the program at individual level

The lifetime costs and QALYs for both intervention and non-intervention groups as well as resulting ICERs are shown in table 1. The cost-effectiveness planes are shown in figure 1. In all analyses, the lifestyle program led to a gain in QALYs and an increase in costs. The ICERs for the lifestyle intervention program were 14,690€ per QALY gained for the 35–54 years olds and 14,372€ per QALY gained for the 55–74 years olds from a payer’s perspective over lifetime. From a societal perspective (including indirect societal costs and direct non-medical cost) the intervention costed −3,805€ per QALY gained for 35–54 year olds and 4,579€ for 55–74 year olds, and dominated the comparator in the younger cohort (was more effective and cost saving). The main driver for cost savings from a societal perspective was the patient time costs (online supplemental file 1, table 7).

Table 1

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Lifetime incremental effectiveness, incremental cost and cost-effectiveness of implementing a lifestyle type 2 diabetes prevention program, by age group and study perspective

Figure 1

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Cost-effectiveness plane: incremental cost and QALYs relative to no intervention in the probabilistic sensitivity analysis. QALYs, quality-adjusted life years.

Sensitivity analysis

The distribution of incremental costs, incremental effects, and cost-effectiveness ratios from PSA is shown in online supplemental file 1, table 4. The CEACs are shown in figure 2, and the probabilities of the intervention to be cost-effective at different WTP thresholds are shown in online supplemental file 1, table 5. At a WTP threshold of 20 000 €/QALY, 50 000€/QALY and 100 000€/QALY, the probability of the intervention to be cost-effective is 65.4%, 98.0%, and 99.8% in 35–54 year olds and 74.0%, 99.2% and 99.9% in 55–74 year olds from a healthcare system perspective over lifetime.

Figure 2

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Lifetime cost-effectiveness acceptability curves from a healthcare system perspective. QALYs, quality-adjusted life years.

The WTP thresholds needed to achieve a probability ≥50% of cost-effectiveness based on CEACs ranged from 14 730 to 15 603 €/QALY. To achieve a probability of cost-effectiveness ≥95%, a WTP of 40 390 to 31 745 €/QALY would be necessary.

Key factors impacting cost-effectiveness calculations in the sensitivity analysis were relative risk reduction of type 2 diabetes, costs of the interventions, and baseline medical costs (online supplemental file 1, table 6 and figure 2).

Discussion

This study is the first to comprehensively examine the long-term cost-effectiveness of introducing a program to prevent type 2 diabetes targeting individuals with intermediate hyperglycemia in Germany. Furthermore, it adds to previous economic evaluations by quantifying the potential impact in two age groups and by two different perspectives (healthcare system and societal) as well as by estimating the potential costs and consequences at the level of a Germany-wide program.

Neumann et al estimated the long-term cost-effectiveness of a hypothetical lifestyle intervention program for the prevention of type 2 diabetes using a four-state Markov model in Germany.12 However, that model did not account for diabetes complications and their costs and did not allow extrapolating the results on a population level.

Only a few studies compared younger and older cohorts in cost-effectiveness analysis, mostly focusing on diabetes screening.33 Furthermore, many other cost-effectiveness analyses ignored indirect societal costs and direct non-medical costs, although it is known from cost of illness studies that those are substantial.27 28

Our main results are comparable with previous international studies, for example, in the UK and the USA.4–6 A recent systematic review evaluating programs to prevent type 2 diabetes reported a median ICER of 13 761 $/QALY (12 653 €/QALY), which is in the same range as our results. While ICERs in each varied between studies, all but one showed ICERs far below the commonly used WTP threshold (US$ 50,000).34

In our study, the intervention in the older group had a higher probability of being cost-effective from the healthcare system perspective compared with the younger group, which agrees with Neumann et al.35 However, from a societal perspective, the intervention in the younger cohort led to lower ICERs and even became cost saving, as the extra productivity losses were only attributed to the under-65 group in our method, so the costs of the diabetes case were higher for them. In the younger group, the effect is more pronounced since this cohort lives longer with diabetes. We showed ICERs for different cost structures, highlighting that it is essential to include direct non-medical and indirect societal costs in the evaluation of population-wide programs to understand their full impact and to avoid underestimation of benefits. In our simulation study, we adapted the CDC-RTI DM to the German setting and relied on the best available German-specific and international data. We also showed the potential cost-effectiveness of a pragmatic lifestyle intervention scaled up to the total population at risk of developing diabetes, which had been done for the USA36 and the UK,7 but not for Germany. This population-level analysis shows that if 25% of people with a HbA1c of 6.0%–6.5% (~2 million people) would participate in the program, one could prevent 10 500 incident cases and gain 35 200 QALYs from a societal perspective over their lifetime. However, such a scenario would come with substantial upfront investments of around 678 million €, which is almost 1.5% of the annual healthcare expenditure for diabetes in Germany.37 In light of around 0.5 million incident cases of diabetes that occur in Germany annually, this highlights that high-risk individual-level prevention strategies as analyzed in this study need to be complemented with population-level policies and interventions that address the upstream determinates of obesity and type 2 diabetes.38–41 Moreover, patient participation in the lifestyle interventions for individuals at risk of diabetes varied from 15% to 80%,42 so our assumption might be considered conservative.

There are strengths and weaknesses of our study. Our strengths included that we used a well-established simulation model for modeling prevention of type 2 diabetes. We parameterized it with epidemiological and economic inputs from German studies that were based on large population-based cohorts or population-representative health insurance claim data. Also, we performed PSA. This analysis, though limited to the healthcare perspective due to software constraints, provides a more comprehensive picture of cost-effectiveness uncertainty compared with univariate analysis.

Our first limitation was that assumptions were required for our simulation analysis. However, we purposely made our assumptions conservative. For example, it is unknown if and how lifestyle programs affect the probability of developing type 2 diabetes beyond the active program phase. We assumed no preventative effect beyond the active program phase. Other assumptions include no reversion from intermediate hyperglycemia to normoglycemia, the same utilities in both intervention and routine care scenarios, adherence equivalent to those in real-world setting studies, etc. A detailed discussion of these assumptions is given in online supplemental file 1.

Our study is also subjected to typical limitations of all simulation studies: dependence on a model structure and parameters. Moreover, not all primary clinical data used in the model are available for Germany; some had to be taken from other countries. The baseline population in the model was parameterized based on the KORA S4 study, a large population-based cohort. KORA was conducted specifically in the Augsburg region, which may not fully represent the entire German population and may not capture all demographic variations across Germany. Regional differences in health outcomes have been observed between northeast and south Germany. Also, the study covers a wide adult age range but does not include very young or very old populations.

We did not include individuals aged 75 and older in our analysis, even though this demographic is growing and increasingly plays a crucial role in national health systems. Assessing the potential effect of the pragmatic lifestyle intervention on this population would indeed be a valuable contribution. However, we chose not to include individuals over 75 years at baseline for two reasons. First, most trial evidence on the effectiveness of lifestyle interventions focuses on individuals younger than 75. Second, our simulation was based on the baseline cohort characteristics from the KORA S4 study, which only includes individuals up to 75 years old. We lacked population-based data on the distribution of risk factors (such as smoking habits, hypertension, and high cholesterol) for those older than 75, which is why they were excluded from our analysis.

Another limitation is that our study did not include program implementation expenses. Moreover, we adopted the costs of the diabetes prevention program directly from Roberts et al,7 which might pose some questions on the transferability as medical care systems and budgeting differ between the UK and Germany. The costs of pragmatic lifestyle interventions varied widely depending on what was included in the program; however, we appointed the program recommended by NICE,6 7 suggesting that the total costs of such a program depend only on the costs of its components in a particular healthcare system. Alternatively, the costs could be taken from another intervention implemented in Germany. Due to the limitations of a Markov model structure, we also could not calculate the loss of productivity due to premature death or identify the largest driver in indirect societal diabetes costs. Unfortunately, no cost structure for any such intervention was found in the literature. However, considering the robustness of our results towards variations in our crucial model assumptions, these limitations are unlikely to change the general conclusions of our study.

In this health-economic analysis, we could not identify which component of the intervention plays the most significant role because this objective was out of scope of this study. As was shown, several key elements contribute to the effectiveness of diabetes prevention programs. The original DPP was a 3-year randomized trial followed by 7 years of modified intervention follow-up, suggesting longer term interventions are beneficial.43 Moreover, flexible interventions delivered by skilled lifestyle coaches that accommodate individual preferences and reflect local community and cultural contexts may achieve better outcomes.44 However, this type of investigation aligns more with the primary objectives of experimental studies.

Conclusion

In our simulation study, we found that a pragmatic lifestyle intervention for preventing type 2 diabetes was highly cost-effective from the healthcare system perspective across all age groups. The intervention in the younger cohort could be cost saving from a societal perspective. If the program was scaled up to a national policy level, the program would prevent more than 10 500 new type 2 diabetes cases over lifetime and need an investment of 1.5% of diabetes-related yearly healthcare expenditures in Germany.

Implementing a type 2 diabetes prevention program like the UK’s NHS-NDPP in Germany would be cost-effective at standard willingness to pay levels. Next to structural upstream prevention approaches, the successful implementation of a lifestyle-based diabetes prevention could be an important component of a successful National Diabetes Strategy in Germany.