A large body of literature has quantified the economic burden of diabetes at the country level. Cost-of-illness studies typically include direct and indirect costs of diabetes. Direct costs comprise all expenditures for the treatment of diabetes, including medication, hospital stays, and treatment of complications.1 Indirect costs are defined as productivity or production losses associated with morbidity and premature mortality.2 Prominent examples of cost-of-illness studies are the cost estimates provided by the American Diabetes Association for the US population: the total burden for 2012 was estimated to be US$245 billion,3 taking increased health expenditure and productivity losses due to diabetes into consideration. In this analysis, indirect costs accounted for 28% of the total costs of diabetes, highlighting the significance of labour market effects for the total economic burden. Evidence of high economic costs, however, is not only limited to developed countries. For example, Seuring and colleagues2 analysed the results of 86 cost-of-illness studies published between 2001 and 2014 and found evidence for a substantial economic burden in low-income and middle-income countries (LMICs), with annual direct costs ranging from INT$242 to $4129 (international dollars; 2011 purchasing power parity) per capita and indirect costs ranging from INT$45 to $16 914 per capita.2
Comparing cost-of-illness studies both within and across countries is challenging because the costs included in the calculations and the methods used to assess costs vary widely in the existing literature. Ettaro and colleagues1 reviewed three decades of primarily US-based cost-of-illness studies and found large discrepancies between studies using differing methods. Similarly, studies4, 5 comparing different costing approaches have illustrated the sensitivity of results to methodological choices.
Few cost-of-illness studies have aimed to quantify the economic burden of diabetes at the regional level. Barceló and colleagues6 estimated a total economic burden for Latin America and the Caribbean of US$65·22 billion in 2000. Indirect costs, evaluated by forgone earnings, constituted 82% of the total costs. In another study7 in the region the economic burden of diabetes and hypertension for the Bahamas, Barbados, Jamaica, and Trinidad and Tobago was quantified and the total costs of diabetes ranged from 0·5% to 5·2% of gross domestic product (GDP). For the WHO African Region in 2005, Kirigia and colleagues8 estimated the cost of diabetes per patient was INT$3633 (using 2005 purchasing power parity), adding up to a total burden of INT$25·51 billion. The share of indirect costs in the study by Kirigia and colleagues8 was 68%, which is slightly lower than what was found by Barceló and colleagues6 for Latin America and the Caribbean.
Research in context
Evidence before this study
We started our literature search by screening studies about the economic costs or labour market consequences of diabetes discussed in a systematic review by Seuring and colleagues. We further searched Google Scholar for articles published before Dec 20, 2016, that either included only the search term “cost(s) of diabetes” alone or the search term “diabetes” in combination with “absenteeism”, “presenteeism”, “sick leave”, “sick days”, “disability days”, “work days”, “workdays”, “productivity”, “labo(u)r market”, “labo(u)r supply”, “indirect cost(s)”, “economic cost(s)”, “economic burden”, “cost burden”, “cost of illness”, “wage(s)”, “earning(s)”, “labo(u)r income”, “labo(u)r force”, “workforce”, “work force”, “employment”, “unemployment”, “direct cost(s)”, “direct expenditure”, or “health expenditure” in the title. We then repeated the above search procedure in PubMed and extended the search to titles and abstracts. Last, we searched for labour market studies cited in relevant cost-of-illness studies identified by the above search, because labour market studies have frequently been used to motivate assumptions for the calculation of indirect costs. 53 labour market studies were identified for high-income countries but only eight studies estimated the labour market consequences of diabetes in low-income and middle-income countries. Additionally, eight cost-of-illness studies aimed to compare the costs of diabetes between countries or world regions.
Added value of this study
To our knowledge, this study is the first to estimate the global costs of diabetes, including both direct and indirect components and to draw comparisons between world regions and countries. Our analysis differs from that in previous studies by building on a large set of labour market studies to motivate assumptions made for the estimation of indirect costs. The study further improves existing direct cost estimates provided by the International Diabetes Federation using a range of patient-level health expenditure ratios derived from the identified literature.
Implication of all the available evidence
This study shows that diabetes imposes an economic burden not only in HICs but also in many LMICs. The global dimension of the problem suggests that adequately addressing diabetes requires increased efforts from the international community. However, data limitations make it difficult to precisely gauge the economic burden of diabetes in many LMICS and further research is necessary to improve knowledge about economic costs of diabetes in understudied regions.
In addition to these regional studies, a small number of studies9, 10, 11 provide cost calculations for the global level. The 2015 version of the International Diabetes Federation's (IDF) Diabetes Atlas9 estimated global health expenditure due to diabetes to be US$673 billion or INT$795 billion (2011 purchasing power parity). Furthermore, a study from the NCD Risk Factor Collaboration10 calculated global direct costs of INT$825 billion (2011 purchasing power parity) for 2014, almost 60% of which arose in LMICs. Bloom and colleagues11 reported estimates of the global direct and indirect economic burden of diabetes, but they did not provide a detailed breakdown of costs by country or world region and did not consider all relevant productivity losses for calculation of indirect costs.
We aimed to estimate the full global economic burden of diabetes by taking into consideration both direct costs and production losses due to morbidity or premature mortality. We applied the same method and cost definition for each country to allow a regional breakdown and ranking of countries by economic costs.
