Analysis of Reasons For Readmission of Diabetic Patients: 2015-2019

Background: Among patients with diabetes who had been hospitalized, 30% had twice or more hospitalisations rate, accounting for more than 50% of total hospitalizations and hospitalization expense. The purpose of our study was to to nd available strategies to reduce the readmission rate of diabetics in rural areas. Methods: This retrospective single-center study used the data from Yongchuan Hospital of Chongqing Medical University. The t-test and the chi-square test or Fisher's exact test were used to compare continuous and categorical variables, respectively. We used the Spearman correlation coecient to examine the relationship between variables. Multiple linear regression was performed to analyze the inuencing factors of hospitalisation time, and dummy variables were set for categorical independent variables. Results: There were a total of 1721 readmissions during a ve-year period; among them, 829 were females and 892 males. The readmission rate of diabetic patients in the endocrinology department was 32.40%. The age, times of hospitalisation, and duration of all subjects were 64.67 ± 13.82, 2.69 ± 1.41 and 10.60 ± 6.78, respectively. Among all the diabetic patients, type 2 diabetes accounted for 98.55% (n = 1696). Most of the patients were readmitted due to poor glycemic control, infection, edema, dizziness, and weakness, accounting for approximately 56%. During the 5-year period, the majority of readmitted diabetic patients were hospitalized twice. Times of hospitalisation was weakly positively correlated with age (Rho = 0.206, P ≤ 0.001), diabetic duration (Rho = 0.248, P ≤ 0.001) and hospitalisation expenses (Rho = 0.008, P = 0.035) by Spearman correlation analysis. Age, duration of diabetes, systolic blood pressure (SBP), diastolic blood pressure (DBP) and alanine aminotransferase (ALT) were the main factors affecting times of hospitalisation in diabetes patients (all P < 0.05). Compared with current smokers, non-smokers and cessation smokers had high hospitalisations rate (all P for trend < 0.05). When taking diabetic foot infection as a reference, edema was more accountable than diabetic foot infection for hospitalisation times, which was statistically signicant (P for trend = 0.048). Conclusion: Age, duration of diabetes and hospitalisation costs were positively correlated with times of hospitalisation. Age, duration of diabetes, blood pressure, ALT, smoking status and edema are the inuencing factors of hospitalisation times. The most common causes of hospitalisation for diabetics are poor glycemic control, infection, edema, dizziness, and weakness. Controlling these factors may be key to developing rational health strategies for rural diabetics.


Introduction
Diabetes, a chronic non-communicable disease, affects thousands of people all over the world. It is reported that there will be an estimated 693 million (9.9%) adult diabetics globally by 2045 [1]. Due to urbanization, aging, increased prevalence of overweight and obesity and genetic susceptibility of Chinese people, the prevalence of diabetes in China is rapidly increasing. Presently, China has become the country with the most diabetes patients in the world.
Diabetes mellitus (DM) can be accompanied by acute and chronic complications, leading to organ dysfunction and failure, and even disability or death. DM is not only a serious health problem facing the world with high disability rate, morbidity and mortality, but also a huge economic burden on individuals, family and society. The total global healthcare expenditure due to diabetes was estimated to be USD 850 billion in 2017, and will increase by 7% to USD 958 billion by 2045 [1]. Analogously, the total annual medical cost of diabetes treatment in China was about 85-100 billion RMB (USD 12.93-15.21 billion) in 2013 [2]. Nevertheless, the health systems in most of the low-or middle-income developing countries are not su ciently equipped to handle the rapidly rising burden of diabetes [3].
Diabetic patients have a higher risk of hospitalisation than non-diabetic subjects, and a large proportion of these hospitalisations are due to diabetes-related complications [4][5][6]. Complications from diabetes are a serious threat to the healthcare system and one of the top ten reasons for readmission in public hospitals worldwide [7]. Among patients with diabetes who had been hospitalized, 30% had twice or more hospitalisations rate, accounting for more than 50% of total hospitalisations and hospitalisation expenses [8]. Therefore, this population-based study aims to analyze the causes of the rehospitalisation of diabetic patients, and proposed guidelines for treatment and follow-up to reduce the number of hospitalisations and the cost of health care.

De nition
We de ned two or more hospitalisations as readmission.

Procedures
The data used in this study were obtained from the medical record department of Yongchuan Hospital of Chongqing Medical University, Chongqing China, a tertiary hospital. The principal diagnosis has been coded according to the Tenth International Classi cation of Diseases (ICD-10) of the World Health Organization at the time of discharge, the information of hospitalized diabetic patients in endocrinology department during the period from January 1, 2015 to December 31, 2019 is retrieved according to the main discharge diagnosis (E10, E11). As we utilized the principal discharge diagnosis to identify diabetic patients; therefore, those patients who were not primarily hospitalized for diabetes or transferred to the endocrinology department because of diabetes-related problems were excluded (Fig. 1). Namely, subjects were admitted and discharged from the endocrinology department. Likewise, patients who were admitted in 2014 and discharged in 2015 were excluded. We used Excel to screen out the information of patients who were hospitalized twice or more. The electronic medical record system was used to search the hospitalisation information according to the patient's hospitalisation number each time. The age, gender, diabetes duration, type of diabetes, smoking, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), glucose (Glu), hemoglobin A1c (HbA1c), triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), alanine aminotransferase(ALT), aspartate aminotransferase (AST), uric acid (UA), serum creatinine (Scr), times of hospitalisation, reasons for admission, hospitalisation costs, and treatment plans were extracted.

Statistical analysis
Descriptive statistics were used to describe clinical characteristics. Continuous variables were shown as Mean±SD, and t-test was used for comparison between groups. Categorical variables were expressed as frequency and percentage, and were compared using the chi-square test or the Fisher's exact test. Spearman correlation coe cient was applied to examine the relationship between variables. Multiple linear regression was performed to analyze the in uencing factors of hospitalisation times, and dummy variables were set for categorical independent variables. A P value < 0.05 (two-tailed) was considered as statistically signi cant. All statistical analyses were performed with SPSS software version 26.0 (SPSS Inc., Chicago, IL).

Analysis of clinical characteristics
During the study period, we totally screened 1721 readmissions with a principal diagnosis of DM (Fig. 1). Further, we calculated the rate of readmission for patients with DM in the endocrinology department was 32.40%.
As shown in Table 1, a total of 829 females and 892 males were included in our study. The age, times of hospitalisation, and duration of all subjects were 64.67 ± 13.82, 2.69 ± 1.41 and 10.60 ± 6.78, respectively (Table 1). Among all the diabetic patients, type 2 diabetes mellitus accounted for 98.55% (n = 1696, Table 1). Interestingly, we found that both males and females did not smoke in the majority (69.61%, Table 1). Compared with males, females had higher BMI, SBP, TC, HDL-C, and LDL-C (P < 0.05), and low levels of DBP, ALT, AST, UA, and Scr (P < 0.05, Table 1). However, there was no signi cant difference in glucose, HbA1c, TG, and hospitalisation costs in rehospitalisation diabetes patients among different gender (Table 1).
Our study found that 773 (44.92%) patients were treated with insulin combined with non-insulin medicines in all readmissions ( Table 1). Most of the patients were readmitted due to poor glycemic control, infection, edema, dizziness, and weakness, accounting for approximately 56% (Table 1). During the 5-year period, most diabetic readmission patients were hospitalized twice (Fig. 2).

The correlation of factors and times of hospitalisation
The correlation between factors and times of hospitalisation were performed with Spearman correlation analysis. As shown in Table 2, times of hospitalisation were weakly positively correlated with age (Rho = 0.206, P ≤ 0.001), diabetic duration (Rho = 0.248, P ≤ 0.001) and hospitalisation expenses (Rho = 0.008, P = 0.035).

Association between other variables and times of hospitalisation
Multiple linear regression was used to investigate the independent correlation between other variables and times of hospitalisation. As shown in Table 3, we found that age, duration of diabetes, SBP, DBP and ALT were the main factors affecting times of hospitalisation in diabetes patients (all P < 0.05). The results showed that there was no statistical difference in the number of hospitalisations between type 1 and type 2 diabetic patients (P for trend = 0.859, Table 4), male and female subjects (P for trend =0.880, Table 4). Surprisingly, compared with current smokers, non-smokers and cessation smokers had higher hospitalisations rate (all P for trend < 0.05, Table 4).
With insulin treatment as the reference, non-insulin medicines (NIM) treatment, insulin+ NIM treatment and GS (glucose solution) treatment had no statistically signi cant effect on the number of hospitalisations (all P for trend > 0.05, Table 4).
When taking diabetic foot infection as a reference, edema was more accountable than diabetic foot infection for hospitalisation times, which was statistically signi cant (P for trend = 0.048, Table 4). However, there was no signi cant difference in the number of hospitalisations for poor glycemic control, diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic syndrome (HHS), hypoglycemia, infection, microalbuminuria, blurred vision, dizziness, headache, chest distress, precordial discomfort, palpitation, dyspnea, chest pain, extremities pain, arthralgia, numbness, paresthesia, low back pain, consciousness disorders, abdominal distention, abdominal pain, vomiting, diarrhea, constipation, urinary incontinence, melena, pruritus, weakness, hepatic dysfunction, elevated blood glucose, and the classic symptoms of DM with diabetic foot infection (all P for trend > 0.05, Table 4).

Discussion
The burden of hospitalized diabetics is huge, rapidly growing and expensive, and readmission is another large part of the burden [9]. In view of the signi cant impact on cost and quality, the hospital readmission rate is increasingly used as an indicator of health care quality and a potential source of regulatory penalties for hospitals [10]. Therefore, some countries use 30-days readmission rates to assess the quality of health care services. However, to the best of our knowledge, the readmission rate has not been taken as a measure of medical quality in China. Moreover, there is a lack of studies to investigate the diabetes readmission in China.
Our results revealed that the readmission rate of diabetic patients in the department of endocrinology at Yongchuan Hospital of Chongqing Medical University was 32.40% in 5 years, which is consistent with Friedman's research that about one-third of diabetic patients had twice or more hospitalisations [11].
Overall, the reason why smokers and non-smokers are readmitted differently is that almost all female patients do not smoke. Furthermore, our study indicated that the most common causes of readmission for patients with DM were poor glycemic control, infection, edema, dizziness, and weakness.
Due to poor blood glucose control can lead to infection and other complications, need hospital treatment, so it is one of the main reasons for readmission. Such as edema, dizziness, weakness are symptoms of chronic complications of diabetes. These symptoms indicate long duration. Our results also show that duration related to the number of hospital, so there are the main reasons for rehospitalisation.
This study ndings are consistent with those of Donnan et al [12] and Strack et al [13], that the readmission rate increases with age. Meanwhile, we also found that the duration of diabetes and hospitalisation costs were positively correlated with times of hospitalisation. Therefore, better glucose control reduction of complications and the times of hospitalisation are the key to reduce the burden of diabetes patients.
By multiple linear regression analysis, not only age and course of disease affected the number of hospitalisation, but it is also affected by blood pressure, ALT and smoking status. Moreover, the edema also affects times of hospitalisation. Although age is immutable, there may be other things they can reduce the readmission of diabetics, such as diabetes education, diabetes self-management, moderate exercise, smoking cessation, blood pressure control and so on.
A series of factors increase hospital readmission among patients with diabetes. Numerous studies that have investigated the risk factors for readmission of patients with diabetes demonstrate gender [14,15], race [8,9], insurance type [8,15], [9,13]urgent or emergent, comorbidity burden [8]. We did not collect some factors and our study period was different; therefore, we could not compare them with previous studies. However, our study helps to develop strategies for risk factors to reduce readmission.
As previous studies have shown that 27 percent of readmissions within 30 days are preventable [16], efforts are needed to reduce this frequency, especially among the elderly. Our ndings show that multiple hospitalisations do not signi cantly change the health status of patients with diabetes, but may increase the number of readmissions. Similarly, adequate discharge planning, patient education, and follow-up actions are most effective in reducing readmission, which is consistent with previous studies [17][18][19]. To reduce readmission rates, we could create structured of individualized discharge plan for each patient with diabetes, as the American Diabetes Association does [20], but we have to be aware of the fact that they rarely follow this plan seriously. Hence, primary medical institutions play an important role in diabetes ambulatory management [21], and the family physician model may make a signi cant contribution to reducing the readmission rate of diabetic patients. For developing countries, these ndings may help to plan future health strategies for diabetes management.
The study has several limitations that should be noted. First, this is a retrospective, observational, singlecenter study of outcomes data. Second, the readmission rate may be underestimated due to the fact that patients may be hospitalized in another medical institution where the hospitalisation records are not available in our hospital database, and patients die during our study period. Third, due to the limitation of China's medical insurance, people who are hospitalized for more than 30 days need to be readmitted.
Therefore, it is possible to overestimate the number of readmissions.

Conclusion
We found that age, duration of diabetes and hospitalisation costs were positively correlated with times of hospitalisation. Age, duration of diabetes, blood pressure, ALT, smoking status and edema were the in uencing factors of hospitalisation times. The most common causes of hospitalisation for diabetics, including poor glycemic control, infection, edema, dizziness, and weakness. The analysis of readmission of diabetic patients can help to plan the health strategy of diabetes management in the future, so as to reduce the readmission rate and the cost of health care.

Funding
This research did not receive any speci c grant from funding agencies in the public, commercial, or notfor-pro t sectors.

Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.    insulin and diabetic foot infection, respectively. Figure 1 Screening of readmitted diabetic patients Distribution of readmission times of diabetic patients in ve years