Introduction
Diabetes mellitus accounted for 77.7 thousand deaths (2.6% of all deaths) and 4.46 million disability-adjusted life years (DALYs) in 2019 in the USA [
1,
2]. Diabetes prevalence has increased rapidly in the USA in recent decades, reaching 11.8% in 2019 [
2,
3]. Diabetes is associated with several diseases including chronic kidney disease (CKD). CKD was the 6th leading cause of death in 2019, accounting for 3.6% of all deaths [
2]. In 1990, CKD, which is preventable by adequate medical care, was the 14th leading cause of death, accounting for 1.5% of all deaths [
2].
The prevalence of diabetes has increased despite previous calls for action
. Recent data from the Behavioral Risk Factor Surveillance System (BRFSS), a large state-based surveillance system, show that the self-reported prevalence of diagnosed diabetes in 2020 was 10.6% among adults aged 18 or older. West Virginia had the highest prevalence (15.7%) and Alabama 14.8%, while District of Columbia (7.5%) and Colorado (7.6%) had the lowest rates [
4].
Obesity increased in all states from 1990 to 2020 [
4]. Obesity is a major risk factor for type 2 diabetes, and there is a significant association between weight gain and diabetes incidence [
5‐
7]. The prevalence of obesity it is likely to continue to rise in the years ahead unless effective interventions are implemented. Furthermore, diabetes is associated with a high medical cost [
8]. Behavioral and metabolic risk factors such as poor diet and lack of physical activity are also risk factors for type 2 diabetes [
9,
10]. Therefore, diabetes is expected to increase rapidly in the coming decades due to aging and growth of the US population, poor diet, obesity, and low physical activity [
11,
12].
Diabetes mortality rates vary by states and counties in the USA, masking disparities [
13,
14]. Knowing where the “hotspots” are will guide health professionals to target high-risk communities using limited resources. This study presents trends in mortality from diabetes and chronic kidney disease for US counties from 1980 to 2014.
Discussion
This study revealed large differences among US counties in mortality rates from diabetes and CKD. The findings showed little improvement in age-standardized mortality rates from diabetes and significant increases in age-standardized mortality rates due to CKD between 1980 and 2014. Diabetes mortality actually increased substantially from 1980 to 2000 with a downward trend thereafter. On the other hand, CKD mortality increased sharply in recent decades. These findings will assist in examining the root causes of these trends and disparities among US counties. Moreover, they will provide valuable insights into developing and implementing programs and policies to reduce the burden and disparities of diabetes and CKD mortality.
This study showed that diabetes mortality has declined at the national level from 2000 to 2014 at a time when the prevalence of diabetes was increasing [
2]. This is the result of a decline in the case fatality rate due to better treatment and management of diabetes. However, there are huge variations in the rate of decline by counties indicating the need for better access to medical care throughout the country [
28].
These results showed a rapid increase in CKD mortality from 1990 to 2014 in the USA. Several studies have reported little improvement in CKD prevalence in the USA from 1990 to 2015 [
29]. This finding is a surprising since there are known effective interventions such ACE inhibitors to prevent CKD progression [
30]. This finding has several implications. CKD is a disease that requires extensive medical care and resources such as dialysis and others [
8]. Indeed, this rise will put a lot of strains on the medical system in the coming years.
CKD mortality due to diabetes and hypertension increased in recent years, underscoring the need for better treatment and management of blood pressure and diabetes. Both diabetes and blood pressure diagnosis and control are not optimal in the USA. Several studies have shown that counties have large variations in diagnoses and control of diabetes and blood pressure [
28,
31]. Early detection through screening of high-risk individuals is crucial to control blood pressure and diabetes and reduce diabetes and CKD burden and mortality [
32]. Early diagnosis will facilitate treatment and behavioral changes and will increase survival. There is a need for more aggressive programs to control blood pressure and diabetes that include medical and preventive care approaches.
Access to and quality of medical care have a major impact on mortality from diabetes and CKD [
33]. Several studies have shown that timely diagnosis of diabetes and CKD and proper treatment reduce the complications and improve the outcome [
32,
34]. Unfortunately, not all US residents have equal access to quality medical care. Both diabetes and CKD require that the patient adhere to long-term management of the condition [
35]. It is possible that proper management of these conditions vary by county and have led to these disparities. However, for many physicians in the USA, especially in poor and rural areas where the patient load is heavy, they have little or no time for patient counselling. In addition, the current health system financing does not reimburse health facilities for time spent on patient education.
Several studies have shown that obesity has rapidly increased in the USA during the time period of this study [
36,
37]. In fact, some studies have called obesity an epidemic as it has impacted all geographic areas and demographic groups [
6]. Recent reports showed a slight improvements in physical activity, but many individuals in the USA do not meet the recommended levels of physical activity [
36]. There is a need for programs to improve physical activity in the USA to reduce the burden of diabetes as well as many other conditions.
Diet is a major risk factor for type 2 diabetes and for CKD [
5]. For example, low intake of whole grains and the consumption of processed food and red meats are known risk factors for type 2 diabetes [
9]. Also, diet high in salt consumption is associated with an increased blood pressure [
38]. The 2019 Global Burden of Disease showed that poor diet is a major cause of type 2 diabetes [
29]. In the USA, diet has not improved much during the study period [
39]. Moreover, there is only limited information on dietary habits at the local level. The only available source for county dietary intake is 6 questions on fruits and vegetables from the behavioral risk factor surveillance system [
40].
The Diabetes Prevention Program and Outcomes Study shows that type 2 diabetes is largely preventable through healthy lifestyle [
41]. The study showed that lifestyle interventions were also cost-effective. However, the long-term effects of such a program have not been well documented. It is time to invest in prevention activities in communities in order to improve behaviors. Perhaps, sponsoring innovations is a mean to find local solutions since counties and communities need financial and technical support to solve these challenges.
Diabetes and CKD are associated with poor quality of life [
42]. Several studies have shown that diabetes patients have more days of poor mental and physical health [
42,
43]. They are more likely to miss work and be less productive [
44]. Therefore, social support initiatives for patients and their care givers are important for improving quality of life.
Our study showed high levels of diabetes and CKD mortality in areas in the South East, especially around the Mississippi river. Previous research has identified differences in socioeconomic status, differences in the prevalence of behavioral and metabolic risk factors, and differences in access to and quality of health care as potential drivers of differences in life expectancy among counties, with risk factors explaining the largest proportion of the differences in life expectancy [
45]. Unfortunately, areas with high diabetes and CKD mortality in our manuscript have high levels of obesity, low levels of physical activity, high levels of smoking, and poor diet. Addressing these risk factors would be the best strategy to reduce the burden of many chronic conditions.
This study has a number of important limitations. First, the data sources underlying this analysis, i.e., deaths, population, and covariates, are each subject to error. Second, the garbage code redistribution methods used for this analysis have not been validated due to a lack of appropriate gold standard data. Third, uncertainty due to garbage code redistribution methods has not been quantified and included in the uncertainty intervals reported for this analysis. Fourth, the small area estimation models smooth mortality rates over space, time, and age group which may attenuate unusually low or high mortality rates, leading to an underestimation of geographic variation.
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