Background
Diabetes mellitus is one of the most common chronic diseases in the United States (U.S.), with an estimated 28.5 million diagnosed cases among adults in 2019 [
1]. Complications of diabetes are a significant public health burden [
2], and result in substantial economic costs to patients and healthcare systems [
3,
4]. Short-term effects of uncontrolled diabetes include acute metabolic complications such as diabetic ketoacidosis or hypoglycemic coma [
5]. Long-term effects of diabetes, on the other hand, are associated with both macrovascular and microvascular complications. The macrovascular complications include cardiovascular disease, peripheral vascular disease, and stroke [
5,
6], while microvascular complications include retinopathy, neuropathy and nephropathy [
5]. Retinal lesions may lead to progressive visual impairment resulting in blindness, while neuropathy increases the risk of lower-extremity ulcerations that may necessitate amputation [
5,
6]. Nephropathy can ultimately progress to end-stage renal disease, requiring chronic dialysis treatment or kidney transplantation [
5,
6]. Such complications can permanently impact quality of life [
7‐
9], and are associated with depression [
10], functional limitations, and premature mortality [
6,
11,
12]. Therefore, the primary goal of diabetes care is to prevent complications through glycemic control and management of cardiovascular risk factors [
13‐
15].
Hospitalizations due to complications of diabetes, which is considered an ambulatory care sensitive condition, often reflect problems with access to or utilization of quality outpatient care [
16‐
19]. Therefore, reducing the burden of potentially avoidable diabetes-related complications represents an important opportunity to improve population health in the United States. This is particularly true in southeastern states, which have the highest burden of diabetes in the nation [
20,
21]. Florida is the most populous state in this region, and it is estimated that at least 2.5 million of the state’s adult residents have diabetes [
22,
23]. While hospitalizations due to diabetes complications may be prevented with timely access to care and effective management [
16], there have been substantial increases in diabetes-related hospitalizations, amputations, and hospital costs in Florida in recent years [
24]. Complications of diabetes will likely present an ongoing challenge in Florida due to the state’s growing population of adults aged 65 and over [
25]. Age is a known risk factor for Type 2 diabetes, which represents 90–95% of the diabetes burden in the U.S. [
6]. Older adults account for the majority of healthcare resource utilization attributable to diabetes [
4], and are also projected to account for most of the future increase in diabetes prevalence in the U.S. [
26]. Reducing the burden of preventable diabetes-related complications represents an important opportunity to meaningfully improve the health of Floridians.
Evidence of disparities in diabetes prevalence and participation in diabetes preventive programs (diabetes self-management education) has been reported in Florida [
27,
28], suggesting that there might also be disparities in complications of diabetes in the state. However, there is a lack of information on distribution or determinants/predictors of diabetes complications in Florida. Since severe complications of diabetes pose the greatest burden to patients and health systems [
29], identifying determinants/predictors of these complications is important for guiding strategies aimed at reducing the burden. Therefore, the objective of this study was to identify individual- and area-level predictors of severe diabetes complications among hospitalized adult patients in Florida.
Results
Descriptive statistics
A total of 1,061,140 hospital records for unique patients between the ages of 18 and 100 with diagnoses of Type 1 or Type 2 diabetes mellitus were included in the study. The median duration of hospitalization was 3 days, with an interquartile range (IQR) of 2 to 6 days and an overall range of 0 to 1,143 days. Median age was 69 years (IQR 58 to 78), and there were more male patients (51.7%) than female patients (48.3%). Most patients were non-Hispanic White (60.6%), followed by Hispanic patients (18.7%) and non-Hispanic Black or African American patients (17.7%) (Table
3). The vast majority (97.3%) of patients had Type 2 diabetes, and the most common comorbidities were hypertension (83.1%) and hyperlipidemia (55.6%). Medicare (64.9%), private insurance (18.3%), and Medicaid (7.5%) were the most frequently listed payment sources. Adapted DCSI (aDCSI) scores ranged from 0 to 11, with a median of 1 and IQR of 0 to 2. Approximately one-tenth (9.8%) of patients in the study had an aDCSI score of 4 or higher.
Table 3
Characteristics and Adapted Diabetes Complications Severity Index (aDCSI) scores of hospitalized adult patients with diabetes
Year of admission | | | |
2016 | 24.4 (258,916) | 24.3 (232,982) | 25.0 (25,934) |
2017 | 23.9 (253,149) | 24.0 (229,394) | 22.9 (23,755) |
2018 | 24.8 (263,102) | 24.9 (237,982) | 24.2 (25,120) |
2019 | 27.0 (285,973) | 26.8 (256,833) | 28.0 (29,140) |
Gender | | | |
Male | 51.7 (548,773) | 50.8 (486,685) | 59.7 (62,088) |
Female | 48.3 (512,367) | 49.2 (470,506) | 40.3 (41,861) |
Race/ethnicity | | | |
Non-Hispanic American Indian/ Alaska Native | 0.13 (1,348) | 0.13 (1,231) | 0.11 (117) |
Non-Hispanic Asian | 0.98 (10,128) | 1.00 (9,343) | 0.77 (785) |
Non-Hispanic Black | 17.7 (183,600) | 17.6 (164,514) | 18.8 (19,086) |
Non-Hispanic Hawaiian/ Pacific Islander | 0.05 (479) | 0.05 (436) | 0.04 (43) |
Non-Hispanic White | 60.6 (628,604) | 60.1 (562,971) | 64.5 (65,633) |
Other non-Hispanic | 1.9 (20,123) | 1.96 (18,350) | 1.74 (1,773) |
Hispanic | 18.7 (193,754) | 19.2 (179,394) | 14.1 (14,360) |
Presence of social security number (SSN) | | | |
SSN provided on admission | 95.9 (1,017,333) | 95.8 (916,990) | 96.5 (100,343) |
No SSN on admission | 4.1 (43,807) | 4.2 (40,201) | 3.5 (3,606) |
Principal payer | | | |
Medicare | 64.9 (689,067) | 63.3 (606,108) | 79.8 (82,959) |
Medicaid | 7.5 (79,339) | 7.7 (73,229) | 5.9 (6,110) |
Private | 18.3 (193,909) | 19.3 (184,498) | 9.1 (9,411) |
VAa, TriCare, federal, state or local government | 2.7 (28,929) | 2.8 (26,523) | 2.3 (2,406) |
Self-pay (uninsured) | 4.7 (49,808) | 5.0 (47,792) | 1.9 (2,016) |
Non-payment | 1.5 (16,073) | 1.6 (15,406) | 0.64 (667) |
Other | 0.4 (4,015) | 0.38 (3,635) | 0.37 (380) |
Diabetes type | | | |
Type 1 | 2.7 (28,815) | 2.7 (25,557) | 3.1 (3,258) |
Type 2 | 97.3 (1,032,325) | 97.3 (931,634) | 96.9 (100,691) |
Diagnosed comorbidities | | | |
Hypertension | 83.1 (882,253) | 82.0 (784,959) | 93.6 (97,294) |
Arthritis | 14.5 (153,460) | 14.5 (139,133) | 13.8 (14,327) |
Hyperlipidemia | 55.6 (590,247) | 54.5 (521,237) | 66.4 (69,010) |
Obesity | 26.8 (284,369) | 26.7 (255,464) | 27.8 (28,905) |
Depression | 12.6 (133,262) | 12.5 (119,797) | 13.0 (13,465) |
Neighborhood Deprivation Index quartiles | | | |
1 (most deprived) | 26.4 (280,228) | 26.5 (253,793) | 25.4 (26,436) |
2 | 29.9 (317,117) | 29.8 (285,679) | 30.2 (31,438) |
3 | 25.8 (273,824) | 25.7 (246,411) | 26.4 (27,413) |
4 (least deprived) | 17.9 (189,971) | 17.9 (171,309) | 18.0 (18,662) |
The number of patients from each ZCTA ranged from 1 to 5,162 with a median of 907 and IQR of 402 to 1,625. Summary statistics of ZCTA-level characteristics, all of which were non-normally distributed, are displayed in Table
4. In 2016, the median numbers of primary care physicians and licensed pharmacies were 6 (IQR 1.7 to 13.6) and 3.1 (IQR 1.3 to 5.5) per 10,000 population, respectively. The percentage of residents with educational attainment below the high school level ranged from 0 to 62.5%, with a median of 10.3%. Other socioeconomic characteristics of ZCTAs also varied widely; for instance, the median unemployment rate was 5.1%, but ranged from 0 to 78.8%. Median value of owner-occupied housing units ranged from $12,800 to $1,208,3300 (median $188,740, IQR $130,420 to $273,460). There was a higher median percentage of females in professional occupations (37.9%) compared to males (28.8%), but the percentage of males in management positions (median 10.6%) tended to be higher than females (median 8.0%). The median percentage of households in poverty was 8.9%, but ranged from 0 to 70.8%. The percentage of non-Hispanic Black residents at the ZCTA level also ranged widely, from 0 to 100%, with a median of 7.9%. Residential stability within a one-year period tended to be high (median 85.6%, IQR 81.8 to 88.6%).
Table 4
Characteristics of ZIP code tabulation areas in Florida, USA
Total population (2015–2019) | 104 | 7,940.5 | 19,030.5 | 31,342.5 | 76,508 |
Healthcare Access (2016) | | | | | |
Primary care physicians / 10,000 pop. | 0 | 1.7 | 6.0 | 13.6 | 7,541 |
Pharmacies / 10,000 pop. | 0 | 1.3 | 3.1 | 5.5 | 390.2 |
Food Environment (2016) | | | | | |
Grocery stores / km2 | 0 | 0.003 | 0.05 | 0.2 | 7.6 |
Convenience stores / km2 | 0 | 0 | 0.02 | 0.1 | 6.7 |
Limited service restaurants / km2 | 0 | 0.01 | 0.2 | 0.8 | 38.2 |
Education (2015–2019) | | | | | |
% ≥ 25 with less than high school education | 0 | 6.3 | 10.3 | 16.7 | 62.5 |
Employment (2015–2019) | | | | | |
Unemployment rate in population 16 years and older | 0 | 3.8 | 5.1 | 7.0 | 78.8 |
% males no longer in work force | 0 | 14.4 | 19.0 | 26.1 | 100 |
Housing (2015–2019) | | | | | |
% renter-occupied housing units | 0 | 19.1 | 27.5 | 41.2 | 100 |
% vacant housing units | 0 | 10.5 | 16.1 | 24.0 | 97.6 |
% crowded (> 1 person/room) | 0 | 0.9 | 2.0 | 3.7 | 47.2 |
% renter/owner costs > 50% of income | 0 | 10.6 | 13.9 | 18.2 | 49.8 |
Median value, owner-occupied housing units | $12,800 | $130,420 | $188,740 | $273,460 | $1,208,300 |
Occupation (2015–2019) | | | | | |
% males in management | 0 | 6.9 | 10.6 | 14.6 | 100 |
% males in professional occupations | 0 | 20.4 | 28.8 | 39.4 | 100 |
% females in management | 0 | 5.4 | 8.0 | 10.8 | 100 |
% females in professional occupations | 0 | 31.6 | 37.9 | 45.8 | 100 |
Poverty (2015–2019) | | | | | |
% households in poverty | 0 | 5.3 | 8.9 | 13.8 | 70.8 |
% female-headed households with dependent children | 0 | 3.1 | 5.1 | 7.5 | 66.0 |
% households earning < $30,000 / year | 0 | 18.5 | 25.7 | 33.4 | 100 |
% households receiving public assistance or SNAPa benefits | 0 | 6.7 | 13.1 | 21.2 | 100 |
% households with no car | 0 | 2.5 | 4.5 | 7.5 | 41.2 |
Racial composition (2015–2019) | | | | | |
% non-Hispanic Black residents | 0 | 2.8 | 7.9 | 17.2 | 100 |
Residential stability (2015–2019) | | | | | |
% in same residence as 1 year ago | 11.9 | 81.8 | 85.6 | 88.6 | 100 |
% 65 years and over | 0 | 13.8 | 19.2 | 27.1 | 87.1 |
Neighborhood deprivation index
The Neighborhood Deprivation Index (NDI) included variables from the following domains: education (percentage of residents at least 25 years of age with education below the high school level), housing (median value of owner-occupied housing units), occupation (percentage of employed males and females 16 and over with management or professional occupations), poverty (percentage of families with income below the poverty level, percentage of households with annual income less than $30,000, percentage of families with public assistance income or in households receiving Supplemental Nutrition Assistance Program (SNAP) benefits), and residential stability (percentage of residents aged 65 and over). Variable loadings on the first principal component, which were used to construct NDI scores, are displayed in Table
5. Across the entire study area, 59.6% of the variance of the ten variables in the index was explained by the first principal component. When PCA was stratified by rurality, the percentage of variance explained was higher for non-rural ZCTAs (65.7%) than for rural ZCTAs (53.6%). Characteristics of the ZCTAs in each NDI quartile are summarized in Table
6. Lower values of the index were associated with higher percentages of the population with less than a high school education, families with income below the poverty level, households with annual income less than $30,000, and families receiving public assistance income. Higher median housing values, percentage of employed males and females with professional or management occupations, and percentage of older adults in the population were associated with higher values of the NDI. Therefore, lower values of the index indicate more deprived areas. Fewer patients (17.9%) resided in ZCTAs in the highest (least deprived) NDI quartile compared to all other quartiles (Table
3).
Table 5
Results of principal components analysis used to construct Neighborhood Deprivation Index for Florida ZCTAs
Education | | | |
% ≥ 25 with less than high school education | -0.78 | -0.91 | -0.84 |
Housing | | | |
Median value, owner-occupied housing units | 0.68 | 0.58 | 0.63 |
Occupation | | | |
% males in management | 0.57 | 0.73 | 0.63 |
% males in professional occupations | 0.76 | 0.77 | 0.77 |
% females in management | 0.36 | 0.62 | 0.48 |
% females in professional occupations | 0.60 | 0.70 | 0.67 |
Poverty | | | |
% of families with income below poverty level | -0.77 | -0.90 | -0.83 |
% households with annual income < $30,000 | -0.83 | -0.89 | -0.86 |
% families with public assistance income or in households receiving SNAPb benefits | -0.82 | -0.98 | -0.89 |
Residential stability | | | |
% of residents 65 years and older | 0.22 | 0.27 | 0.24 |
Percent of variance explained | 53.6% | 65.7% | 59.6% |
Table 6
Median values of ZIP code tabulation area characteristics by Neighborhood Deprivation Index (NDI) quartile
% ≥ 25 with less than high school education | 20.6 | 12.7 | 8.5 | 4.4 |
Median value, owner-occupied housing units | $105,580 | $157,250 | $207,160 | $347,240 |
% males in management | 5.6 | 8.9 | 11.8 | 17.9 |
% males in professional occupations | 16.5 | 25.8 | 32.5 | 47.4 |
% females in management | 5.1 | 6.7 | 9.0 | 12.0 |
% females in professional occupations | 28.7 | 35.0 | 41.2 | 50.5 |
% families with income below poverty level | 17.8 | 10.8 | 7.1 | 4.2 |
% households with annual income < $30,000 | 38.4 | 29.1 | 22.2 | 16.0 |
% families with public assistance income or in households receiving SNAPa benefits | 27.3 | 16.8 | 10.3 | 4.0 |
% residents 65 years and older | 16.5 | 19.6 | 19.7 | 21.8 |
Population average generalized linear model
Significant individual-level predictors of severe diabetes complications (aDCSI score ≥ 4) included age, gender, race/ethnicity, diabetes type, comorbidities (hypertension, hyperlipidemia, obesity, depression and arthritis), payer, report of an SSN upon admission, and year of admission (Tables
7 and
8).
Table 7
Predictors of severe diabetes complications among hospitalized adults in Florida, USA, 2016–2019
Intercept | -4.416 | -4.496 | -4.335 | < 0.0001 |
Age | 0.040 | 0.037 | 0.043 | < 0.0001 |
Age (quadratic) | -0.0002 | -0.0002 | -0.0002 | < 0.0001 |
Gender | | | | |
Male | 0.398 | 0.381 | 0.416 | < 0.0001 |
Female | Ref. | - | - | - |
Race/ethnicity | | | | < 0.0001 |
Non-Hispanic American Indian/Alaska Native | 0.123 | -0.151 | 0.397 | 0.3777 |
Non-Hispanic Asian | -0.088 | -0.183 | 0.008 | 0.0718 |
Non-Hispanic Black or African American | 0.238 | 0.207 | 0.268 | < 0.0001 |
Non-Hispanic Hawaiian/ Pacific Islander | 0.098 | -0.383 | 0.578 | 0.6906 |
Other non-Hispanic | -0.070 | -0.149 | 0.009 | 0.0812 |
Hispanic | -0.243 | -0.277 | -0.210 | < 0.0001 |
Non-Hispanic White | Ref. | - | - | - |
Diabetes type | | | | |
Type 2 | -0.976 | -1.017 | -0.934 | < 0.0001 |
Type 1 | Ref. | - | - | - |
Comorbidities | | | | |
Hypertension | 0.833 | 0.804 | 0.862 | < 0.0001 |
Hyperlipidemia | 0.258 | 0.243 | 0.273 | < 0.0001 |
Obesity | 0.211 | 0.194 | 0.229 | < 0.0001 |
Depression | 0.089 | 0.069 | 0.109 | < 0.0001 |
Arthritis | -0.216 | -0.237 | -0.194 | < 0.0001 |
Principal payer | | | | < 0.0001 |
Medicare | 0.615 | 0.587 | 0.642 | < 0.0001 |
Medicaid | 0.606 | 0.568 | 0.644 | < 0.0001 |
VAa, TriCare, gov’t | 0.285 | 0.233 | 0.337 | < 0.0001 |
Uninsured | -0.043 | -0.096 | 0.010 | 0.1104 |
Non-payment | -0.019 | -0.106 | 0.067 | 0.6586 |
Other | 0.450 | 0.337 | 0.562 | < 0.0001 |
Private | Ref. | - | - | - |
Presence of social security number (SSN) | | | | |
No SSN on admission | 0.105 | 0.067 | 0.143 | < 0.0001 |
SSN on admission | Ref. | - | - | - |
Admission year | | | | < 0.0001 |
2017 | -0.086 | -0.105 | -0.066 | < 0.0001 |
2018 | -0.067 | -0.088 | -0.049 | < 0.0001 |
2019 | -0.011 | -0.030 | 0.008 | 0.2613 |
2016 | Ref. | - | - | - |
Neighborhood Deprivation Index quartile | | | | |
Lower 3 quartiles | 0.090 | 0.064 | 0.117 | < 0.0001 |
Least deprived quartile | Ref. | - | - | - |
Interaction term | | | | < 0.0001 |
Male | | | | |
Non-Hispanic American Indian/ Alaska Native | -0.233 | -0.615 | 0.148 | 0.2299 |
Non-Hispanic Asian | -0.147 | -0.289 | -0.005 | 0.0421 |
Non-Hispanic Black or African American | -0.055 | -0.092 | -0.019 | 0.0033 |
Non-Hispanic Hawaiian/ Pacific Islander | -0.198 | -0.860 | 0.464 | 0.5579 |
Other non-Hispanic | 0.091 | -0.011 | 0.194 | 0.0817 |
Hispanic | 0.098 | 0.059 | 0.136 | < 0.0001 |
Female, non-Hispanic White | Ref. | - | - | - |
Table 8
Odds ratios for predictors of severe diabetes complications among hospitalized adults in Florida, USA, 2016–2019
Intercept | 0.012 | 0.011 | 0.013 | < 0.0001 |
Age | 1.041 | 1.038 | 1.044 | < 0.0001 |
Age (quadratic) | 0.9998 | 0.9998 | 0.9998 | < 0.0001 |
Gender & race/ethnicity | | | | |
Males | | | | |
Non-Hispanic American Indian/Alaska Native | 0.896 | 0.666 | 1.205 | 0.4675 |
Non-Hispanic Asian | 0.791 | 0.716 | 0.873 | < 0.0001 |
Non-Hispanic Black or African American | 1.200 | 1.168 | 1.233 | < 0.0001 |
Non-Hispanic Hawaiian/ Pacific Islander | 0.904 | 0.587 | 1.395 | 0.3326 |
Other non-Hispanic | 1.021 | 0.958 | 1.089 | 0.5223 |
Hispanic | 0.864 | 0.840 | 0.889 | < 0.0001 |
Non-Hispanic White | Ref. | - | - | - |
Females | | | | |
Non-Hispanic American Indian/Alaska Native | 1.131 | 0.860 | 1.487 | 0.3777 |
Non-Hispanic Asian | 0.916 | 0.833 | 1.008 | 0.0718 |
Non-Hispanic Black or African American | 1.269 | 1.230 | 1.307 | < 0.0001 |
Non-Hispanic Hawaiian/ Pacific Islander | 1.103 | 0.682 | 1.782 | 0.6906 |
Other non-Hispanic | 0.932 | 0.862 | 1.009 | 0.0812 |
Hispanic | 0.784 | 0.758 | 0.811 | < 0.0001 |
Non-Hispanic White | Ref. | - | - | - |
Diabetes type | | | | |
Type 2 | 0.377 | 0.362 | 0.393 | < 0.0001 |
Type 1 | Ref. | - | - | - |
Comorbidities | | | | |
Hypertension | 2.300 | 2.234 | 2.368 | < 0.0001 |
Hyperlipidemia | 1.294 | 1.275 | 1.314 | < 0.0001 |
Obesity | 1.235 | 1.214 | 1.257 | < 0.0001 |
Depression | 1.093 | 1.071 | 1.115 | < 0.0001 |
Arthritis | 0.806 | 0.789 | 0.824 | < 0.0001 |
Principal payer | | | | |
Medicare | 1.850 | 1.799 | 1.900 | < 0.0001 |
Medicaid | 1.833 | 1.765 | 1.904 | < 0.0001 |
VAa, TriCare, gov’t | 1.330 | 1.262 | 1.401 | < 0.0001 |
Uninsured | 0.958 | 0.908 | 1.010 | 0.1104 |
Non-payment | 0.981 | 0.899 | 1.069 | 0.6586 |
Other | 1.568 | 1.401 | 1.754 | < 0.0001 |
Private | Ref. | - | - | - |
Presence of social security number (SSN) | | | | |
No SSN on admission | 1.111 | 1.069 | 1.154 | < 0.0001 |
SSN on admission | Ref. | - | - | - |
Admission year | | | | |
2017 | 0.918 | 0.900 | 0.936 | < 0.0001 |
2018 | 0.935 | 0.916 | 0.952 | < 0.0001 |
2019 | 0.989 | 0.970 | 1.008 | 0.2613 |
2016 | Ref. | - | - | - |
Neighborhood Deprivation Index quartile | | | | |
Lower 3 quartiles | 1.094 | 1.066 | 1.124 | < 0.0001 |
Least deprived quartile | Ref. | - | - | - |
Coefficients for linear and quadratic age terms in the final model had opposite signs, such that the odds of severe diabetes complications were higher for older patients, but the magnitude of this effect diminished as age increased. Racial and ethnic differences in the odds of severe diabetes complications differed by gender. For instance, among males, the odds of severe complications were 21% lower for Asian patients compared to non-Hispanic White patients (95% confidence interval [CI]: 0.72, 0.87, p < 0.0001), but a significant difference was not observed among female patients (p = 0.0718). On the other hand, while Hispanic male patients also had lower odds of severe complications compared to non-Hispanic White male patients (odds ratio [OR] = 0.86, 95% CI: 0.84, 0.89, p < 0.0001), the magnitude of the difference between these groups was greater among females (OR = 0.78, 95% CI: 0.76, 0.81, p < 0.0001). In contrast, both male (OR = 1.20, 95% CI: 1.17, 1.23, p < 0.0001) and female (OR = 1.27, 95% CI: 1.23, 1.31, p < 0.0001) non-Hispanic Black patients had higher odds of severe diabetes complications compared to non-Hispanic White patients.
Several clinical factors were associated with the severity of diabetes complications among hospitalized adult patients with diabetes. For instance, the odds of severe diabetes complications were 62% lower for patients with Type 2 compared to Type 1 diabetes (95% CI: 0.36, 0.39, p < 0.0001). Diagnoses of hypertension (OR = 2.30, 95% CI: 2.23, 2.37, p < 0.0001), hyperlipidemia (OR = 1.29, 95% CI: 1.27, 1.31, p < 0.0001), obesity (OR = 1.24, 95% CI: 1.21, 1.26, p < 0.0001) and depression (OR = 1.09, 95% CI: 1.07, 1.11, p < 0.0001) were associated with higher odds of severe diabetes complications, while arthritis was associated with lower odds of severe complications (OR = 0.81, 95% CI: 0.79, 0.82, p < 0.0001).
Lack of health insurance coverage was not a significant predictor of the severity of diabetes complications when compared to private insurance (p = 0.1104). However, patients with Medicare (OR = 1.85, 95% CI: 1.80, 1.90, p < 0.0001), Medicaid (OR = 1.83, 95% CI: 1.77, 1.90, p < 0.0001), VA and other government insurance (OR = 1.33, 95% CI: 1.26, 1.40, p < 0.0001), and other insurance sources (OR = 1.57, 95% CI: 1.40, 1.75, p < 0.0001) did have higher odds of severe complications compared to private insurance. Absence of an SSN upon hospital admission was also positively associated with severe diabetes complications (OR = 1.11, 95% CI: 1.07, 1.15, p < 0.0001). Patients admitted in 2017 (OR = 0.92, 95% CI: 0.90, 0.94, p < 0.0001) and 2018 (OR = 0.94, 95% CI: 0.92, 0.95, p < 0.0001) had slightly lower odds of severe complications than those admitted in 2016.
Neighborhood Deprivation Index (NDI) quartile was the only significant ZCTA-level predictor in the final model. Compared to patients living in ZCTAs in the least deprived quartile, patients in all other NDI quartiles had significantly higher odds of severe diabetes complications (OR = 1.09, 95% CI: 1.07, 1.12, p < 0.0001). Food environment, healthcare access, and racial composition variables were not significantly associated with severity of diabetes complications.
Discussion
This study investigated and identified predictors of severe complications among adult patients hospitalized with diabetes in Florida. The odds of severe complications increased with age, a finding that likely reflects duration of the condition, which is associated with macrovascular events in affected patients [
63]. The observed association between Type 1 diabetes and severe complications is also likely related to duration of the condition, since Type 1 diabetes tends to have an earlier age of onset than Type 2 diabetes [
5]. The diminishing magnitude of the strength of association between older age and severity of complications observed in this study might be due to survival bias since higher aDCSI values are associated with higher risks of death [
29,
37].
Several comorbidities were positively associated with severe diabetes complications, highlighting the difficulties of managing multiple chronic conditions. Patients with multiple conditions face challenges with coordination and quality of care, financial costs, and adhering to complex self-management recommendations [
64]. Hypertension and hyperlipidemia, two important cardiovascular risk factors, were predictors of severe diabetes complications, consistent with findings of a previous study which reported that hypertension and/or hypercholesterolemia in patients with diabetes were predictors of poor health status [
65]. Interestingly, having a diagnosis of arthritis was associated with lower odds of severe complications. While most evidence suggests that multiple conditions are associated with poorer quality of care, this may vary depending upon the specific combination of illnesses [
64]. Further investigation is warranted to understand the mechanism of the negative association between arthritis and severe diabetes complications observed in this study.
Higher odds of severe diabetes complications were observed among patients with a diagnosis of depression compared to those without this diagnosis. Previous research has identified a bi-directional association between diabetes and depression, and the two conditions share risk factors such as socioeconomic deprivation [
66]. The association between depression and severe diabetes complications observed in the current study could reflect the impacts of diabetes complications on quality of life [
66]. This finding may also have been driven by poorer adherence to treatment and self-management recommendations among patients with diabetes who also have depression [
66]. The association observed in this study underscores the importance of depression screening for patients with diabetes, as well as ensuring linkage to additional care when indicated [
66].
There were racial/ethnic and gender disparities in the odds of severe diabetes complications, with non-Hispanic Black patients having significantly higher odds of severe complications than non-Hispanic White patients. In addition to having higher odds of severe complications, non-Hispanic Black patients tended to be younger, with the lowest median age (62 years) of any group in the present study. In comparison, non-Hispanic White patients had a median age of 70 years. These findings are consistent with those of a New York City study that reported younger average age for Black patients with diabetes compared to White patients and lower relative proportions of Black patients in older age groups [
40]. The observed disparities in age and odds of severe complications could, in part, reflect earlier onset of diabetes among Black patients in Florida. They may also indicate disparities in the provision and quality of diabetes care [
67‐
69], and may suggest earlier diabetes-related mortality among Black patients [
40].
While previous studies have reported lower levels of glycemic control [
70] and a higher prevalence of complications [
71,
72] among Hispanic patients with diabetes compared to White patients, Hispanic patients in this study had lower odds of severe complications, a difference that was most pronounced among females. Previous research investigating predictors of severe diabetes complications in a Medicare population had the opposite finding [
61]. This discrepancy could, in part, reflect differences between the compositions of the Hispanic populations of Florida and the U.S. overall. Diabetes prevalence in the Hispanic population in the U.S. varies by country of origin, with the highest diabetes prevalence and diabetes-related mortality rates among those of Mexican descent [
70,
73,
74], who represent a much smaller percentage of the Hispanic population in Florida (13.5%) compared to the U.S. overall (59.5%) [
75]. Significantly lower diabetes prevalence and mortality have been reported among Cubans and Cuban Americans, the largest subgroup of the Hispanic population in Florida [
75]. Given the evidence of inequalities in diabetes prevalence, control, and outcomes within the Hispanic population, considering this diverse population as a single group may mask important differences between subgroups [
74,
76]. However, detailed ethnicity information was not recorded in the hospitalization data, precluding more detailed investigation in the current study.
There is mixed evidence regarding the occurrence of diabetes complications among Asian Americans, who experience higher incidence of some complications, such as end-stage renal disease, and lower incidence of others (lower extremity amputations) compared to their non-Hispanic White counterparts [
72]. In this study, Asian male patients had lower odds of severe complications compared to non-Hispanic White males, but no such difference was observed for Asian female patients, despite findings of a previous study that reported lower diabetes prevalence among females in all Asian subgroups [
77]. The observed finding may reflect gender-based differences in psychosocial factors, health behaviors, and access to healthcare as well as other resources necessary for effective management of the condition [
67,
78,
79]. However, this finding could also be a result of relative sample size in the current study. In 2019, Asian Americans represented 2.6% of Florida’s population [
31], and Asian patients comprised an even lower percentage of the study population (0.98%, 10,128 patients). It is also worth noting that previous research has reported differences in the prevalence of diabetes, as well as risk factors and comorbidities, between different subgroups of the Asian population [
77,
80]. Therefore, it is possible that differences in the severity of diabetes complications existed between subgroups of Asian patients in the current study. Unfortunately, this could not be investigated in this study because more detailed patient information was not available.
The odds of severe complications were higher among both Medicaid and Medicare patients than those with private insurance. As of July 2022, Florida is one of twelve states that have not adopted the Medicaid eligibility expansion of the Affordable Care Act, and therefore non-elderly, low-income adults in the state must meet additional criteria to be eligible for Medicaid [
81]. These criteria include blindness and disability [
82], both of which can result from complications of diabetes, which may partially explain the observed association. In addition, given the income eligibility threshold for Medicaid recipients, these patients are likely to face additional financial barriers to securing the resources and care necessary for effective diabetes control, despite having health insurance coverage. The higher odds of severe diabetes complications among Medicare patients compared to those with private insurance may reflect the older age of Medicare-eligible patients, and longer duration of diabetes in these patients. In addition, end-stage renal disease, a potential consequence of diabetic nephropathy [
5], is one of the eligibility criteria for Medicare [
83], which may also partly explain the observed association.
Lack of health insurance was not significantly associated with having severe diabetes complications when compared to private health insurance coverage. This was somewhat surprising, since health insurance coverage is a predictor of receiving quality diabetes care [
68,
84]. The reason for this finding is unclear, although it could reflect utilization of care. As inpatient hospitalization carries a large cost burden, those without health insurance coverage may decline necessary care for financial reasons. This may have, in part, accounted for the low level of uninsurance among patients in the study (4.7%) compared to the overall population of Florida, which has the fourth-highest percentage of uninsured individuals in the nation (13.4%), although this difference could also reflect the older age of the hospital patients in this study, most of whom were insured with Medicare. In addition, it is possible that some individuals who forego purchasing health insurance coverage due to cost may do so in part because of younger age and fewer health conditions, which could have contributed to the lack of observed association between uninsurance and severity of complications in this study. It is also important to note that only patients’ health insurance coverage at the time of hospitalization was available, and prior insurance status was unknown. Since diabetes complications may result from cumulative years of inadequate glycemic control and cardiovascular risk factor management [
85], and previously uninsured patients may qualify for public health insurance due to end-stage renal disease, blindness, or disability, health insurance coverage throughout the life course may be a better predictor of this outcome. Regardless, the persistence of disparities in severe diabetes complications despite controlling for health insurance suggests that barriers to diabetes control outside of the healthcare setting should also be investigated. Indeed, socioeconomic disparities in avoidable hospitalizations and lower extremity amputations due to diabetes have been reported in Canada, a country with universal access to healthcare [
86].
In addition to the observed association between Medicaid coverage and severe complications, two other findings of this study suggest that socioeconomic position is related to the occurrence of severe diabetes complications. First, the odds of severe complications were higher among patients not reporting a social security number (SSN) than among those that did. It is worth noting that patients who do not report an SSN tend to be from vulnerable groups who may have lower access to healthcare and other important resources than those who do. Such groups may include temporary workers, undocumented immigrants, and those experiencing homelessness [
38]. The higher odds of severe diabetes complications in these patients in the current study suggests that they face barriers to effective diabetes management. In addition, neighborhood deprivation, which is a function of educational attainment, housing value, occupation, poverty, and residential stability, was also a predictor of severe diabetes complications. This association underscores the importance of the living environment, which can impact the ability of patients with diabetes to effectively manage the condition and prevent complications. Residents of more deprived neighborhoods may have fewer opportunities for education and employment, and face both social and physical barriers to engaging in recommended health behaviors [
87].
Strengths and limitations
This study investigated a large sample of hospitalized adult patients with diabetes in Florida who were diverse with respect to demographic characteristics, health insurance coverage, and socioeconomic status. Previous studies that have investigated claims data from a single insurance payer have limited generalizability to patients with different insurance sources or without health insurance coverage. The use of hospital data in this study also prevented bias associated with self-reporting, a limitation of survey data. In addition, while some studies investigating the association between diabetes-related outcomes and socioeconomic position have substituted area-level measures for individual income, this analysis accounted for the nested nature of the data using population average models estimated with generalized estimating Eqs. [
88,
89].
However, this study is not without limitations. A limited number of individual-level variables that reflect individual socioeconomic position (health insurance coverage and presence of a Social Security Number) were available for analysis. Study findings may have also been affected by differences in healthcare utilization, since the financial burden of hospitalization may lead patients with limited resources to decline necessary care. Further investigation of emergency department visits and outpatient stays is warranted to assess the potential impact of healthcare utilization bias on the findings of this study. These limitations notwithstanding, this study provides valuable information for guiding the development and implementation of health programs in Florida to reduce disparities in preventable complications of diabetes in the state.
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