Epidemiology and Economics: the two important e’s in diabEtEs

The epidemiology and the economic impact of diabetes are intimately intertwined. With the increase of the prevalence of type 2 diabetes this invariably not only impacts the health of the population, but also the costs to individuals and healthcare systems. From another perspective epidemiology and economics of diabetes are also linked in the fact that certain populations face higher rates of diabetes as well as worse outcomes due to barriers to access to care.

The burden of diabetes and its causes

The International Diabetes Federation (IDF) estimated that in 2021 there were 537 million people aged 20–79 with diabetes. This is estimated to increase by 46% globally between 2021 and 2045 with the majority of these additional cases in low- and middle-income countries (LMIC).¹ In 2017 there were 9 million people with type 1 diabetes worldwide with an overall global increase in incidence of 3%.² Parallel to this increase in the numbers of people with diabetes the costs of diabetes are increasing, with the IDF estimating that total health expenditure on diabetes was close to US$ 1000 billion in 2019.¹ Beyond the costs of diabetes linked to the increasing numbers of people with the condition, complications, and new medicines and technologies, there is the need to consider how the economic situation of individuals might impact their risk of developing diabetes as well as their diabetes management if they have already diabetes.³ These so called social determinants of health include the environments where people are born, live and interact with different institutions including the healthcare system.

Social determinants of diabetes

In focusing on these determinants various factors such as ethnicity, being a migrant, racism, socio-economic position, education level and living in an urban or rural setting can all negatively impact the onset and the outcomes of diabetes. These different factors can affect incidence and prevalence trends, risk, access to health systems and medicines, as well as healthy lifestyles.

The lack of continuous access to enough food for a healthy life, defined as food insecurity, is more present in people with diabetes than in those without.⁴ This phenomenon impacts poorer individuals. Food insecurity is a risk factor for diabetes and has an impact on the management of diabetes. Being in a food-insecure environment can increase obesity and weight gain, as less healthy food is less expensive. For people with diabetes the high cost of healthcare and food might result in neglecting healthcare in favor of securing food supply. In addition, food insecurity can have an impact on mental health which also complicates diabetes management.

In the United States different social risk factors exist between black and white populations, resulting in prevalence of diabetes being 11% higher in black versus white Americans.⁵ The drivers of this difference are financial factors, food insecurity and unstable housing. In addition to epidemiological differences noted between different ethnic groups, epidemiology is important in disaggregating overarching ethnic groups into sub-groups to better understand factors linked with diabetes. For example overall prevalence of diabetes in the Asian population was 19,1% (NHANES data 2011–2016), however in looking at the different sub-populations within this overall category it was found that prevalence was significantly different in East Asians versus South Asians.⁶

Migration is another determinant to consider. This relates to factors of education, language, culture, and religion. These can all impact food and lifestyle practices as well as access to healthcare systems and the interactions with the system.⁷ Beyond these factors exposures prior to migration need to be considered, for example fetal or early-life malnutrition. Considerations also need to be given to how long the migrants have lived in their host countries and how their original culture has evolved to being closer to that of the country where they live, referred to as acculturation. This acculturation can relate to language proficiency as well as lifestyle with both positive and negative impacts. For example, fluency in the local language means no communication barriers regarding the healthcare system, but dietary changes possibly have a negative impact.

Racial disparities in diabetes prevalence are clearly the result of a variety of social determinants of health. Racism can also be seen as a social determinant of health with racial disparities both impacting the factors leading to diabetes, such as poverty and food security, but also, in regard of racism within healthcare institutions, impacting the responses certain populations receive from the healthcare system.⁸

Another disparity that is often ignored is that of urban versus rural populations. Traditionally, rural areas are perceived as being healthier than urban areas. However, a shift in mortality patterns occurred in the 1970s in the United States.⁹ This was caused by higher rates of smoking, hypertension and obesity, less leisure time physical activity as well as higher poverty rates. Beyond these factors there are also healthcare system-related barriers with less access to healthcare facilities.

The impact of these different factors on the onset and management of diabetes is presented in Figure1.

Access to diabetes care

Access to healthcare beyond geographic access or cultural/racial barriers is compounded by financial aspects. In some contexts, with Universal Health Coverage, costs are covered in part or fully by the government or insurance schemes meaning that the cost burden is not on the individual. However, in the United States regarding the uninsured population as well as in many LMIC the full cost of medicines and care is on the individual. In countries where there is no financial protection, poor and vulnerable populations will thus not be able to access and afford the care they need to manage their diabetes. In a study on admissions for diabetic ketoacidosis in an inner city setting in the United States it was found that in 68% the main cause was stopping insulin due to financial reasons.¹⁰ Lack of resources to afford insulin and other elements of diabetes care is also a problem in many LMICs: for example in Mali the full amount of the lowest paid government worker’s monthly salary is needed to pay for a month of diabetes care.¹¹ In LMICs lack of access to insulin and diabetes care results in high rates of mortality. The fact that 100 years after the discovery of insulin many people still fail to access this life-saving medicine highlights the global inequity that exists between healthcare systems.

Conclusion

These epidemiological and economic factors are important to understand as for diabetes a life course approach is important, with social determinants shaping fetal, childhood and adolescent health and contributing to adult onset of diabetes. This is irrespective of the worrying increases in childhood obesity and type 2 diabetes. To address these disparities intensified efforts in social public health policies are required tackling economic, social, and environmental determinants of health. Responses are also needed for people with diabetes to ensure access to care, medicines and insulin. Healthcare system responses need to consider all the elements above and these measures need to address different sub-populations: people at risk of diabetes; obese individuals; people with impaired fasting glucose; those with undiagnosed diabetes; people with diabetes and those with complications. For innovations in this area it will be necessary to consider how wide social problems are addressed, just new pharmacological interventions are not enough.