Survival Analysis on Time-To-Recovery of Diabetic Patients at Minlik Referral Hospital, Ethiopia: Retrospective Cohort Study

Aim The study aimed to determine the time to recovery of diabetic patients who have been treated in the hospital under follow-up. A retrospective cohort study design was carried out. The fast blood glucose level of diabetic patients who are under follow-up in the hospital was measured from 2016 to 2020. One thousand seven hundred diabetic patients were included in the study. Kaplan-Meier, Log-rank test, global test, Schoenfeld residuals, and Cox-PH model were used for statistical analysis. agents

There are three main types of diabetes: type I, type II, and gestational age. Of these, type II occurs in almost all cases (Grossman and Grossman, 2017;Ababa, Id and Id, 2019; 'Comparative Study Of Some Immunological Aspects Between Type I And Type II Diabetic Mellitus In Iraqi Patients Of Thi-Qar', 2020).
Diabetes is directly related to high blood pressure so that it is important to measure and treat the blood pressure (Grossman and Messerli, 2011;Muleta et al., 2017;Akalu and Belsti, 2020).
In summary, it is important to identify and treat the causes, as the disease may not be cured by nature, but may be treated with a variety of therapies and interventions. Therefore, the aim of the study is to assess the time to recovery of diabetic patients who have been treated in the hospital under follow-up.

Materials And Methods
Study design, setting and Sample size The study was conducted at Minlik Referral Hospital, Ethiopia, found in the capital city of Ethiopia, Addis Ababa. The data was measured by the blood glucose level of diabetic patients at the hospital, covering the period from 2009 to 2016, and 1278 patients were eligible for the study.
Data collection, procedure and quality control Data collectors also participated in the hospital's staff and experts in the eld. The data has been monitored and veri ed by experts based on the questionnaire checklist developed by the researchers.
Data were categorized, compiled, coded, and checked for completeness, accuracy.

Data processing and analysis
The data were entered into SPSS (version 20) and exported to R-software (version 4.06) for analysis.
Descriptive statistics have been applied to analyze patient characteristics such as mean, variance, median, percentile, and proportions of two groups (Kaplan-Meir). A survival model such as the Coxproportional model was used to assess the hazard effect of seemingly signi cant predictors of the outcome variable. The p-value <0.05 was considered statistically signi cant.

Variables of Study
The dependent variable would be divided into two categories: Time to recovery of diabetic patients is an event while withdrawal from follow-up from different reasons and death are considered as censored. When the variable is properly measured, it serves as a key pillar for data analysis and discussion, as well as conclusions. The following are the main factors that affect the outcome variable: Sex of Patients, Types of Diabetes, Age of Patients, Past Medical History, Family History, Complication, Marital Status, Employee Status, Spdrt, SBP, DBP, Weight, and Time..
Type II diabetic miletus: Type 2 diabetes mellitus (DM) is a chronic metabolic disorder in which prevalence has been increasing steadily all over the world (Olokoba, Obateru and Olokoba, 2015).
Type I diabetic mellitus: It often starts in childhood. However, it can start in adulthood (Johns Hopkins University and Johns Hopkins Health System, 2011).
Hypertension: Hypertension is de ned as a systolic blood pressure of 140 mm Hg or greater and/or a diastolic pressure of 90 mm Hg or greater in subjects who are not taking antihypertensive medication (Pardi et al., 2009).

Results
Out of the total of 1278 participants, 27.4% were censored (withdrawal from follow-up, death), and 72.6% recovered from the diabetic disease (Table 1).   Table 2 also presents the minimum and maximum follow-up per week were respectively 0 and 318. 15.6% of female patients and 11.7 % of male patients lost follow-up.
33.3% of male and 39.4% female patients recovered from diabetic disease. Generally, female patients had more time to recover from the diabetic disease (Table 2, Figure 1).
Patients with systolic blood pressure below, normal and high were 5.2%,8.7%, and 13.5% respectively censored, and 13.5%,22.5%, and 36.6% of patients with systolic blood pressure respectively were recovered from the disease(Table 3, Figure 10). Patients with diastolic pressure below, normal and high were 0.5%,10.5%, and 27.4% respectively censored, and 1.2%,27.2%, and 72.6% of patients with systolic blood pressure respectively were recovered from the disease(Table 3, Figure 9).
7.5% of patients who had a past medical history and 19.4% of patients who had no past medical history lost to follow-up. 20.9% of patients who had past medical history recovered from the disease, and 51.7% of patients who had no past medical history had recovered from diabetic disease (Table 2, Figure 4). 5% of Patients that family history and 22.4% of patients whose family history was censored. 14.2 % of patients whose family history recovered from the disease, and 58.4% of patients who had family history recovered from the disease (Table 2, Figure 5).

Discussion
The diabetic disease or diabetes is not curable. The cause of the disease is high blood sugar in the blood.
However, it is possible to treat through medication and traditional methods. The aim of the study focused on determining the time to recurrence of diabetic patients over the entire follow-up period at Minlik Referral Hospital, Ethiopia, found in Addis Ababa, headquarter of Ethiopia. The retrospective cohort study was conducted. The data were analyzed by R-software (version 4.05).
Among the total of 1278, 72.6% of diabetic patients experienced to time to recovery of diabetic patients and 27.4% loss to follow up from study. The mean and median of time to recurrence of diabetic patients respectively are 50.48 and 32. The estimated survival function curve for patients with Type II DM is above that of diabetic patients with type I DM over the entire follow-up period, giving evidence for the higher probability of survival and lower risk of recovery for patients with type II DM as compared with patients with type IDM. It indicated that patients with type II DM have better recovery time than diabetic patients with type I DM, which is consistent with the study in Palestinian (Salameh et al., 2019), Gurage Zone (Migora et al., 2021), Amhara region (Getie et al., 2021),Rwanda (Bavuma et al., 2020).
Patients with high systolic blood pressure (SBP) are high percentage to time-to-recover of diabetic patients as compared to patients with below and normal systolic blood pressure and similar results from patients with high diastolic blood pressure (Muleta et al., 2017).  Figures (2-10)). The graphs for all categorical variables are fairly at; the assumption of proportionality is not (much) violated (Figures 11, 12, 13). Thus, the global test and Schoenfeld residuals showed the assumption of the Cox proportional model is met.
Non-linearity assumption is not the problem for categorical variables, however, non-linearity assumption is a problem of continuous variables. Plotting martingale residuals is to detect the non-linearity assumption of the Cox proportional hazard model. Thus, there is no speci c pattern for the dependent variable versus the weight of patients, therefore the assumption of the model is not violated (Figure 14).  (30-44, 45-59, 60-74,>74), past medical history, family history, health complication, education status, marital status, SBP and DBP and types of diabetic Mellitus at baseline are not signi cant effect for time to recurrence of diabetic patients, hence these variables are not included in multivariable analysis (Table 7). Considered Cox-PH model ) and the result of multivariable analysis, the tted model can be: ) For interpretability, the hazard ratio for the parameter estimates estimated. For sex, The expected hazard is 1.322 times higher in male than female diabetic patients or there is a 32.2% increase in the expected hazard in males relative to female diabetic patients holding other variables are constant, which is consistent with the study done (Hanefeld et al., 1996;Icks et al., 2012;Whitaker et al., 2014;Muleta et al., 2017;Tachkov et al., 2020).  Schoenfeld residuals of Complication, past medical history, Family history and marital status Figure 13 Schoenfeld residuals for Weight, Spdrt, educational status, SBP, Employe status, DBP and Regimen Figure 14