Introduction

Obesity is a serious global health problem which brings substantial economic burden to society. Worldwide rates of obesity have nearly tripled since 1975 and more than 2.1 billion people (30% of global population) suffer from overweight or obesity today. Importantly, obesity is a risk factor for cardiovascular diseases, type II diabetes and some types of cancers, which brings substantial healthcare costs, but also large indirect costs through lost productivity. The global economic impact of obesity is estimated to be $2 trillion (2.8% of global GDP), which is comparable to the impact of armed conflict, smoking or terrorism [1]. In OECD countries, 8.4% of healthcare budget is dedicated to treatment of overweight-related diseases [2].

Obesity has become a pressing concern also with regard to the COVID-19 pandemic. Numerous studies have shown that overweight and obese individuals are more at risk for being COVID-19 positive and have more severe symptoms, leading to significant increase in morbidity and mortality [3]. Moreover, due to many restrictions implemented in order to prevent the spread of COVID-19 (e.g. movement restrictions, social distancing), people lack physical activity which may aggravate current trends in the prevalence of obesity and put even larger strain on the healthcare system [3].

In the Czech Republic, the rates of obesity have been increasing since the 90’s both in adults [4] and children [5]. The goal of this study is to estimate the social costs of obesity, defined as BMI > 30 kg/m2, in the Czech Republic. The cost-of-illness (COI) approach, which views the burden of specific illness as the sum of direct (medical) and indirect costs, is implemented. The resulting social costs of obesity show us how much could be saved if the disease did not exist at all [6]. This study is being novel in estimating the social costs of obesity in the Czech Republic using the COI method, demonstrating what an extreme burden this disease brings to the society.

Literature review

Direct costs

Numerous studies have found that obesity is associated with increased risk of cardiovascular diseases, type II diabetes and cancers [7, 8]. This leads to increased medical costs due to higher use of prescription drugs and outpatient care, or longer hospital stays as a result of post-treatment complications [9,10,11,12]. Current literature indicates that the direct costs of obesity are substantial. For instance, research from the USA indicates that obesity is associated with 36% increase in inpatient and outpatient spending and 77% increase in medication costs [13]. Several studies also show that medical costs increase proportionally with BMI [14,15,16].

Table 4 summarizes literature focusing on direct costs of obesity. The studies vary in the amount of comorbidities included, which ranges from 4 to 18. The share of direct costs of obesity on total healthcare costs ranges from 2.3% in Sweden [16] to 6.7% in Canada [17]. In the Czech Republic, the direct costs of obesity were estimated as 7.6 billion CZK (excluding the costs of pharmacotherapy) in 2013, which accounted for 3.45% of total healthcare costs [18]. Earlier estimate from 2007 was 9.5 billion CZK (5.2% of healthcare costs), out of which 2.6 billion CZK were costs of pharmacotherapy [19]. In general, the share of costs of overweight and obesity on total healthcare costs ranges between 2 and 8% [2].

Indirect costs

Absenteeism

Absenteeism refers to absence from work due to illness. The rate of absenteeism due to illness varies across countries, but Czech Republic has one of the highest rates in Europe, reaching on average 16.3 days missed in 2018 [20].

Table 5 summarizes literature which includes the costs of absenteeism associated with obesity. Almost all studies find that the costs of absenteeism are significantly larger for obese workers compared with normal-weight workers. However, the magnitude of the difference varies across studies, which can be caused by country, data or methodology differences. Usually, absenteeism is compared between obese and normal weight individuals (e.g. [9, 21, 22]), but some studies compare BMI > 25 (thus including overweight) with normal weight (e.g. [11, 23,24,25]), which makes some results uncomparable. Studies which examine absenteeism across three obesity classes show that the rates of absenteeism increase with BMI [21, 22, 26].

Presenteeism

Presenteeism refers to reduced productivity at work due to presence of mental or physical health complications [27]. There is growing evidence that the costs of presenteeism associated with chronic conditions largely exceed the costs of absenteeism [28,29,30].

To the best of our knowledge, presenteeism related to obesity has not been measured in the Czech Republic thus far, therefore, our estimates are based on current literature, which is summarized in Table 6. All the studies find that obesity is positively associated with presenteeism, but the extent differs across studies. Compared with normal weight individuals, the estimates range from 1.1 to 3.8 more days lost [31,32,33,34] and reach 22.7–33 days lost for obesity class III [28, 35].

Premature mortality

Excess weight is associated with substantial increases in early mortality [36]. Obesity and its related diseases are estimated to reduce life expectancy by 0.9–4.2 years [2], which leads to large productivity losses. Current literature on the costs of premature mortality related to obesity is summarized in Table 7. The estimates of number of years lost due to obesity-related premature mortality vary across studies and substantially increase with BMI [37]. In the Czech Republic, overweight-attributable reduction in life expectancy is estimated to be 3.5 years [38] and in 2013, the obesity-related costs due to premature mortality were evaluated as 1.2 billion CZK [18]. In general, the studies show that the costs are larger for men than women, typically due to higher wages, higher retirement age or higher prevalence of obesity.

Estimates from the Czech Republic

Only a few studies estimated the social costs of obesity in the Czech Republic. In 2007, the direct costs of obesity were estimated as 9.5 billion CZK [19]. Another estimate which is largely based on other (foreign) studies estimated direct and indirect costs of obesity to be 20.3–42.5 billion CZK and 17.2–37.8 billion CZK, respectively [39]. In 2013, direct and indirect costs of obesity were quantified as 12.1 billion CZK and corresponded to 0.3% of GDP in 2013 [18].

Data and methodology

Data

Table 1 summarizes the data used in the baseline model. The healthcare utilization costs and costs of pharmacotherapy in 2018 are obtained from the General Health Insurance Fund (GHIF) jointly for men and women [40], which are extrapolated to the whole population.Footnote 1 The data for computation of costs of absenteeism and premature mortality in 2018 are obtained from the Institute for Health Information and Statistics (IHIS), specifically from the Information System Incapacity for work [41] and the Information System Deaths [42]. For each comorbidity, they are available for 5-year age groups for men and women separately. The estimation of costs of presenteeism is based on literature review.

Prevalence of obesity in the Czech Republic is taken from the NCD Risk Factor Collaboration (NCD-RisC) study with the most recent data being from 2016. This study provides the prevalence of obesity in 200 countries based on data measured by physicians. The age-standardised prevalence of obesity in population 20 years and older is 27.3% for men and 26.5% for women [43]. Relative risks are derived from Guh et al. [7] and Dobbins et al. [8]. These studies provide a review of existing studies that identify statistically significant comorbidities of obesity, i.e. the diseases that are more likely to occur in obese population vs. normal weight population. Guh et al. (2009) conduct a review of studies coming predominantly from the USA (55%) and Europe (40%), and Dobbins et al. (2013) conduct a review of studies conducted mainly in the USA, Norway, Sweden or Japan.

Paid work is valued by the average gross salary for each gender and age group in 2018 reported by the Czech Statistical Office (CSO) [44]. The average daily amount of hours spent doing housework was estimated to be 3 h for women and 2 h for men [45]. The value of unpaid work is approximated by the average wage of cleaning services workers in 2018 (the average hourly wage is 87 CZK/h [46]). Life expectancy in 2018 is derived from the CSO [47] and the number of employed people aged 25-64 years in 2018 is obtained from Eurostat [48].

Table 1 Data sources
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Methodology

Social costs of obesity are estimated using the cost-of-illness (COI) approach, which views the economic burden of disease as the sum of several categories of direct and indirect costs [49]. There are two types of approaches within the COI methodology: prevalence and incidence approach. The prevalence approach is used in our analysis as it assesses the current economic burden of illness [50]. For more details on methodology, please refer to Appendix B.

Direct costs

Direct costs refer to medical and non-medical expenditures related to obesity-related diseases and are estimated using the top-down approach. This approach uses population attributable fraction (PAF) which attributes part of healthcare costs to obesity. Due to data constraints specific to the Czech Republic, the computation of direct costs is divided into healthcare utilization costs and costs of pharmaceuticals.

Based on two studies [7, 8], 20 comorbidities of obesity and their relative risks RR (how much more likely will these diseases occur in obese individuals compared to normal weight) are identified. Using RR and prevalence (p) of obesity in the Czech Republic from the NCD RisC study, \(PAF_c\) (i.e. what portion of comorbidity’s costs are due to obesity) is computed:

$$\begin{aligned}PAF_c = \dfrac{p\cdot (RR_c-1)}{p\cdot (RR_c-1)+1}\end{aligned}$$

Healthcare costs attributable to obesity (HC) are computed as:

$$\begin{aligned}HC = \sum_{c} PAF_c \cdot C_c,\end{aligned}$$

where \(PAF_c\) is population attributable fraction for comorbidity c and \(C_c\) are the healthcare utilization costs associated with comorbidity c.

Similar approach is taken in estimating the costs of pharmacotherapy attributable to obesity. Based on two studies [19, 23], five groups of pharmaceuticals are identified (e.g. pharmaceuticals used in the cure of diabetes mellitus, cardiovascular diseases etc.) along with the specific Anatomical Therapeutic Chemical (ATC) classification codes (see Appendix B for more details). Pharmaceutical costs attributable to obesity (PC) are computed as:

$$\begin{aligned} PC = \sum _{c} PAF_{c} \cdot PC_c, \end{aligned}$$

where \( {PC}_c\) are the pharmaceutical costs of ATC group related to a comorbidity c.

Indirect costs

Indirect costs refer to the value of lost production due to morbidity and mortality, which we estimate using the Human capital approach (HCA). We include the costs of absenteeism, presenteeism and premature mortality. The value of both paid work (\(PW_{ag}\)) and unpaid work (\(UW_g\)) is included in the costs, monetized by average gross salary (\(GS_{ag}\)) and average wage of houseworker (\(W_{HW}\)), respectively:

$$\begin{aligned} P_{ag} =PW_{ag} \cdot GS_{ag} + UW_g \cdot W_{HW}, \end{aligned}$$

where \(P_{ag}\) refers to age- (a) and gender- (g) specific evaluation of productivity lost. \(PAF_{acg}\) specific for age (a), comorbidity (c) and gender (g) is used to determine the obesity-attributable productivity lost, because the data are stratified by 5-year age groups and genders.

Absenteeism refers to missed days at work due to illness. The number of days absent (\( {DA}_{acg}\)) due to obesity related comorbidities (c) for age (a) and gender (g) is multiplied by \( {PAF}_{acg}\) to find the number of days absent from work due to obesity (\(DA^{{obesity}}_{acg}\)):

$$\begin{aligned}{DA}^{{obesity}}_{acg} = {DA}_{acg} \cdot PAF_{acg}, \end{aligned}$$

The indirect costs due to obesity-related absenteeism (\( {IC}^{abs}\)) are computed as:

$$\begin{aligned} IC^{abs} = \sum _{a}\sum _{c}\sum _{g} DA^{obesity}_{acg} \cdot P_{ag}. \end{aligned}$$

Presenteeism describes lower productivity while present at work. Due to unavailability of data on obesity-related rates of presenteeism in the Czech Republic, we estimate the costs based on literature review, assuming that on average, obese individuals miss 2 days of work due to presenteeism. In case of presenteeism, we only distinguish the costs for each gender g, disregarding their age as we do not have data for it. The indirect costs due to obesity-related presenteeism (\({IC}^{pres}\)) are computed as:

$$\begin{aligned} IC^{{pres}} = \sum _g p_g \cdot E_g \cdot PL \cdot P_{g}, \end{aligned}$$

where \(E_g\) is the number of employed people in working-age population and \(p_g \cdot E_g\) is the number of obese people in labour force (\(p_g\) is gender-specific prevalence of obesity in working-age population, i.e. 25–64 years old), PL stands for productive days lost due to presenteeism and \(P_g\) is the gender-specific valuation of paid and unpaid work.

To estimate the value lost due to premature mortality, we use the data on number of deaths due to each comorbidity of obesity stratified by gender and age. The present value of future lost earnings (NPV) is computed using a discount rate (i) which is 3% in the baseline scenario:

$$\begin{aligned} NPV = \sum _{t=0}^n \dfrac{{FV}}{(1+i)^t}, \end{aligned}$$

where FV stands for future value and t is the amount of years lost.

The indirect costs due to obesity-related premature mortality (\(IC^{{mort}}\)) are computed as:

$$\begin{aligned} IC^{{mort}}&= \sum _{a}\sum _{c}\sum _{g} PAF_{acg} \cdot M_{acg} \\ & \quad \cdot \left( 0.5 \cdot P_{ag} + \sum _{t=1}^{ret-1} \dfrac{P_{ag}}{(1+i)^t} + \sum _{t=ret}^{{exp}} \dfrac{UW_g \cdot W_{HW}}{(1+i)^t} \right) , \end{aligned}$$

where \(M_{acg}\) stands for age-, comorbidity- and gender-specific number of deaths. Only half of the productivity is accounted for in the first year (\(t = 0\)) to correct for different occurrences of death during the year. The productive years (i.e. before retirement age ret) are monetized by the value of paid and unpaid work, while the years after retirement until life expectancy age exp are monetized by the value of unpaid work only. Only part of these costs is attributable to obesity, which is computed using the \( {PAF}_{acg}\).

Sensitivity analysis

In sensitivity analysis, we test the robustness of results by varying several parameters of the model (more details are available in Sect. B.3):

  • PAF are recomputed using the 95% confidence interval of relative risks.

  • PAF are recomputed using the relative risks from the Dynamo project.

  • Prevalence data from the EHES/EHIS study from 2014 [51, 52] are used.

  • Discount rate of 1% and 5% is used for computing the costs of premature mortality.

  • Unpaid work is completely excluded from total costs.

  • Presenteeism is computed for missing 1, 3 and 4 days of work (baseline value is 2 days).

Results

Direct costs

Healthcare utilization costs

Table 9 lists the relevant comorbidities of obesity along with the ICD-10 codes and PAF computed based on the prevalence of obesity in the Czech RepublicFootnote 2 and relative risks [7, 8]. Total costs of healthcare utilization due to obesity are reported in Table 10 and amount to 11.4 billion CZK (see Fig. 1). The largest portion of these costs is due to type II diabetes mellitus (2.3 billion CZK), ischemic heart disease (2.1 billion CZK) and osteoarthritis (1.9 billion CZK).

Fig. 1
figure 1

Source: author’s computations

Healthcare utilization costs

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Costs of pharmacotherapy

Figure 2 summarizes the costs of pharmacotherapy. Table 11 shows the ATC groups included in the study and the costs attributable to obesity [19, 23]. Drugs used in diabetes make up the largest part of pharmacotherapy costs (820 million CZK), followed by antithrombotic agents (595 million CZK) used for the cure of cardiovascular diseases and agents acting on the renin-angiotensin system (573 million CZK) used for the cure of cancer. Total pharmacotherapy costs attributable to obesity are 3.1 billion CZK.

Fig. 2
figure 2

Source: author’s computations

Costs of pharmacotherapy

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Indirect costs

The indirect costs are visually summarized in Fig. 3.

Absenteeism

2.8 million days were lost due to obesity in men and 2.6 million days in women in 2018. Total costs of absenteeism are 9.2 billion CZK (4.1 billion CZK for women and 5.1 billion CZK for men) and 8.1 billion CZK (3.5 billion CZK for women and 4.6 billion CZK for men) after excluding the value of unpaid work. The results are summarized in Table 12.

Presenteeism

The baseline value for days lost in our model is 2 days of work lost, which is associated with costs of 7.1 billion and 6.2 billion after excluding the value of unpaid work. The costs of presenteeism for 1, 3 and 4 days lost amount to 3.5, 10.6 and 14.1 billion CZK respectively (3.1, 9.3 and 12.3 billion CZK, respectively, after excluding the value of unpaid work). The costs of presenteeism are summarized in Table 13.

Premature mortality

In 2018 women lost 72, 670 years due to obesity, from which 2947 years were productive years. Men lost in total 89, 850 years due to obesity, from which 8737 years were productive years. The reason why the productive years make such a small part of total years lost due to obesity is that most people die due to obesity-related diseases after retirement. Using the discount rate of 3%, the costs of premature mortality due to obesity are 10 billion CZK, including unpaid work. The costs are higher for women even though the amount of productive years lost is lower compared to men because women lose more unproductive years than men. After excluding the unpaid work, the costs are 3.7 billion CZK. Table 14 shows the results for different discount rates.

Fig. 3
figure 3

Source: author’s computations; UW unpaid work

Summary of indirect costs

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Summary of results

Total costs of obesity in the Czech Republic for the year 2018 are summarized in Table 2. In total, they amount to 40.8 billion CZK, which corresponds to 0.8% of GDP in 2018 [53]. The indirect costs account for majority of the costs: 26.3 billion CZK (65%), whereas the direct costs are 14.5 billion CZK (35%), which accounts for 3.4% of total healthcare costs in 2018.Footnote 3

Table 2 Summary of results
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Sensitivity analysis

Table 3 shows the change in costs attributable to obesity as the key parameters are varied. Total costs range between 32.3 billion CZK (− 20.8% from baseline values) and 51.1 billion CZK (+25.5% from baseline values). The largest changes result from using the low and high relative risks values (95% CI). The overall costs decrease by 8.4% when the 2014 data on prevalence of obesity are used.

Table 3 Sensitivity analysis
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Discussion

The goal of this study was to estimate the social costs of obesity in the Czech Republic in 2018. The resulting costs are equal to 40.8 billion CZK, which corresponds to 0.8% of GDP. This result should be taken as a lower-bound estimate of the costs of obesity as the prevalence data come from 2016, we use a very conservative estimate for the costs of presenteeism, we exclude intangible costs and use the top-down approach. The comparison of results across studies is complicated due to differences in methodological approach. A study from Germany, which is socio-economically similar to the Czech Republic, estimated the costs of overweight (BMI > 25) in 2008 using a similar approach as 0.5% of GDP [24]. This estimate is lower than ours mainly because it uses older data: both the prevalence of obesity and healthcare costs have increased largely since 2008.

A new OECD study estimates the burden of overweight and obesity (BMI > 25) in 52 different countries to be 1.6–5.3% of GDP [2]. The specific estimate for the Czech Republic is 4% of GDP, which is much higher than our estimate. This may have several reasons. Our study focuses purely on obesity (BMI > 30), whereas the OECD study also includes overweight (i.e. BMI > 25). The prevalence of overweight is much higher than of obesity in the Czech Republic: 70% for men and 55% for women. Furthermore, the OECD study uses different methodological approach (a microsimulation model vs. a country-level COI study) and data sources (often derived from other countries or studies), so the results are not directly comparable (see Appendix C for more details).

The direct costs of obesity are 14.5 billion CZK, corresponding to 3.4% of healthcare expenditures. International studies estimate the impact of overweight and obesity on health expenditures in the range of 2–7.9% [2]. The estimate from Germany from 2008, which has the same healthcare financing scheme, is 3.27% of healthcare expenditures [24]. The indirect costs are 26.3 billion CZK, which exceeds previous estimates from the Czech Republic due to inclusion of presenteeism, unpaid work, use of gross salaries and rising prevalence of obesity.

Cost-of-illness methodology is the most common measurement approach to estimate the burden of disease, but it has certain drawbacks. A variety of approaches within the COI methodology can be taken, which limits the comparability of results across studies. Additionally, it measures the value of individual’s life only in terms of the production evaluated by average wage, ignoring other dimensions of illness and death, such as pain and lower quality of life [50]. However, when performed with a clear explanation, COI studies represent an important analytic tool in public health policy [55].

In this study, HCA is used to estimate the indirect costs of obesity. This method has been mainly criticised for assuming full employment in the economy, which relates mainly to the costs of absenteeism where every day the worker misses is regarded as lost production. However, the approach disregards the fact that the work can be made up by the worker after his/her return, or it can be done by his/her colleagues [50]. The friction cost approach (FCA) solves this drawback and counts the productivity losses only for the time it takes to replace the absent worker. The HCA is further criticised for evaluating the costs based on age- and gender-specific wages, implying that people earning lower wages are less valuable for the society. Willingness-to-pay approach mitigates this problem, however, it is not often employed as it requires extensive surveys of preferences and the results highly depend on the individuals’ subjective responses to hypothetical questions [55].

There are several limitations in our study, mainly related to availability of relevant data. Firstly, we use the data on prevalence of obesity from 2016, even though we estimate the costs of obesity in 2018 as no more recent data stratified by gender and age groups are available. The results of the EHES 2019Footnote 4 survey suggest increasing trends of obesity, which would imply even larger social costs [56]. Secondly, the relative risks used in computations of population attributable fractions (PAF) and the rate of presenteeism are based on foreign literature. This is the reason why we also perform a thorough sensitivity analysis and vary some of the key parameters of the model. It is evident that foreign data have limited relevance in the Czech Republic. For further improvement of the analysis, it will be necessary to conduct a survey in the Czech Republic.

Our study demonstrates that the costs of obesity are considerable in the Czech Republic and comparable to the costs of smoking and alcohol consumption, which are estimated as 14.5 billion CZK (0.8% of GDP) in 1999 [57] and 59.5 billion CZK (1.2% of GDP) in 2016 [58], respectively. However, smoking and alcohol consumption have received more consistent attention in clinical practice and public health policy [13]. Similarly as alcohol consumption and smoking, early onset of obesity or overweight significantly increases the probability of being obese in adulthood [59]. This implies that obesity is a serious disease which should no longer be regarded as a lifestyle issue but needs to be recognised as a serious medical condition [60].

Conclusion

The rising prevalence of obesity has been putting an increasing pressure on the health care system and society, which will be further aggravated due to the COVID-19 pandemic. The goal of this study was to quantify the extent of this burden in the Czech Republic using data from 2018. The social costs of obesity are estimated using the cost-of-illness approach. Total costs of obesity are estimated to be 40.8 billion CZK, which corresponds to 0.8% of GDP in 2018. Out of this, 14.5 billion CZK (35%) are attributable to direct costs and 26.3 billion (65%) are attributable to indirect costs. The direct costs account for 3.4% of total healthcare costs in 2018. Within indirect costs, the largest part is attributable to premature mortality (10 billion CZK), absenteeism (9.2 billion CZK) and presenteeism (7.1 billion CZK).

This is a unique country-level COI study which focuses on the costs of obesity in the Czech Republic and accounts for several groups of direct and indirect costs. These costs are substantial which is supported by the fact that they are comparable to the costs of smoking or alcohol consumption in the Czech Republic. Moreover, with rising prevalence of overweight and obesity in children and adults, these costs are likely to increase. A comprehensive, systemic program of multiple interventions should be implemented to increase awareness, reverse the trend of growing rates of obesity and save money in the long-term horizon.