Diabetic Retinopathy and Its Associated Factors Among Type Two Diabetes Mellitus Patients: A Cross‐Sectional Study

ABSTRACT

Background

Diabetic retinopathy (DR) is a serious sight‐threatening microvascular complication of type two diabetes mellitus. Globally, it is one of the leading causes of irreversible vision loss. Ninety‐three million people live with diabetic retinopathy suffer some sort of eye damage worldwide.

Objective

To assess the prevalence of diabetic retinopathy and its associated factors among type two diabetes mellitus patients who attend diabetic unit of Hiwot Fana Specialized Hospital, 2021.

Methods

An institutional based cross‐sectional study was conducted among type two diabetes mellitus patients. The data were collected using semi structured questionnaire and direct eye examination with Slit‐Lamp bio‐microscopy. “Multivariable logistic regression was used to identify factors associated with diabetic retinopathy, with adjusted odds ratios (AORs) and 95% confidence intervals (CIs) reported. Statistical significance was considered at p < 0.05”.

Results

The prevalence of DR was 27.6% with 95% CI (22%–34%). Being less than 60 years old (AOR = 0.28, 95% CI: 0.09, 0.84), having comorbid hypertension (AOR = 8.63, 95% CI: 2.51, 29.75), glycemic control less than seven (AOR = 0.06, 95% CI: 0.01, 0.28), having family history of DM (AOR = 3.29, 95% CI: 1.02, 10.67), less than 5 years' diabetes duration (AOR = 0.18, 95% CI: 0.06, 0.61) were factors significantly associated with diabetic retinopathy.

Conclusion

This study revealed a high prevalence of diabetic retinopathy among T2DM patients in Eastern Ethiopia. Key associated factors included duration of diabetes, older age and poor glycemic control. These findings highlight the urgent need for routine ophthalmologic screening and targeted diabetes education in this population.

Abbreviations

AOR

adjusted odds ratio

BDR

baseline diabetic retinopathy

BMI

body mass index

BUN

blood urea nitrogen

CCR

creatinine clearance rate

CKD

chronic kidney disease

Cr

creatinine

FBS

fasting blood sugar

HbA1c

hemoglobin A1c or glycated hemoglobin

IRMAS

intra‐retinal microvascular abnormalities

NPDR

non‐proliferative diabetic retinopathy

PDR

proliferative diabetic retinopathy

SBP

systolic blood pressure

UK

United Kingdom

1. Introduction

Diabetes mellitus (DM) is a metabolic disorder of carbohydrate, fat, and protein in which there are high blood sugar levels over a prolonged period. DM has become one of the most significant non‐communicable diseases worldwide, with the number of affected adults rising rapidly over the past decades. Type 2 diabetes mellitus (T2DM) represents the vast majority of these cases and is responsible for multiple long‐term complications that affect patients' quality of life [1]. Currently, diabetes mellitus is the most common cause of both moderate or severe visual impairment and blindness [2].

T2DM is well understood as a serious public health concern with an underline impact on human life and health expenditures. Fast economic advance and urbanization have a tremendous impact on escalating the burden of diabetes in different parts of the world [3]. The global prevalence of diabetes in 2019 is predicted to be 9.3% (463 million people) escalating to 10.2% (578 million) by 2030 and 10.9% (700 million) by 2045 [4].

International Diabetes Federation (IDF) has estimated that the number of adults with diabetes in Africa will twofold in 20 years, from 12 million in 2010 to 24 million in 2030. People with T2DM have a great risk of developing a number of serious life‐threatening health problems and complications which increase medical care costs and lower the quality of life. These complications are caused by both macro vascular and microvascular complications for instance, cardiovascular diseases, diabetic eye disease, diabetic nephropathy, and diabetic polyneuropathy [5].

Diabetic retinopathy (DR) is a common microvascular complication of diabetic mellitus which causes irreversible blindness. Worldwide, DR accounts for about 5% of all blindness and afflicted 2 million people throughout the globe [5]. DR is a progressive malady of the retinal microvasculature and it is one of the sixth leading causes of global visual impairment [6]. The report of IDF showed that diabetic retinopathy is the leading cause of blindness in working‐age adults and affects more than one‐third of the 425 million adults (20–79 years old) with diabetes [4].

Globally, more than 93 million people suffer from some form of diabetes‐related eye damage. This phenomenon makes DR the leading cause of new blindness in 25‐ to 74‐year‐olds [7]. The prevalence of diabetic retinopathy in the United Kingdom (UK) was 28.3% [8]. On the other hand, in Iran it was 41.9% [9]. Furthermore, the number of peoples with visual impairment which is caused by DR is intensifying globally, accounting for an increasing proportion of all blindness. Age‐standardized prevalence of DR‐related blindness was higher in sub‐Saharan Africa and South Asia [10]. The prevalence of DR was lowest in Europe at 20.6%, South East Asia at 12.5% and highest in Africa at 33.8%, the Middle East and North Africa at 33.8% and the western Pacific region at 36.2% [11]. The prevalence of diabetic retinopathy in Ethiopia was 19.48% [12].

Different solid risk factors are associated with progression and severity of DR among T2DM. For instance, independent risk factors for any diabetic retinopathy included, diabetes duration, HbA1c, serum glucose, and systolic blood pressure, treatment with insulin [13]. On the other hand, there are studies which indicate significant predictors of diabetic retinopathy include, obesity, age, male sex, lower education level [13, 14].

Diabetic retinopathy, which is often early undiagnosed and treated late, has long‐term consequences and is increasingly becoming a leading cause of blindness, especially in developing countries [15]. However, early detection and prompt treatment allow the prevention of visual impairment due to diabetes [14]. As a key intervention, WHO evidence showed that good control of diabetes and hypertension significantly minimizes the risk for diabetic retinopathy [16].

Early screening and treatment can prevent many cases of blindness caused by diabetic retinopathy [17]. Despite the fact that early diabetes screening has a significant impact on lowering the risk of diabetic retinopathy, routine early diabetes screening is not a common practice in developing countries [18]. Early diagnosis and on‐time treatment have a tremendous impact on the prevention of diabetes‐related visual impairment [14].

In Ethiopia, there is an insufficient number of studies regarding the prevalence and associated factors of diabetic retinopathy among T2DM [19]. Even though, there are studies which investigate the prevalence of diabetic retinopathy and its associated factors in some parts of the country [13].

Eastern Ethiopia has unique sociocultural dynamics, limited ophthalmic service availability, and prolonged travel distances to referral centers, lower screening uptake, and higher proportions of poorly controlled diabetes. These contextual factors may contribute to a different or elevated risk profile for diabetic retinopathy compared to other Ethiopian regions; however, empirical data from this zone remain scarce [20]. Therefore, this study was undertaken to determine the prevalence of diabetic retinopathy and its associated factors among type two diabetes mellitus patients in Eastern Ethiopia.

2. Materials and Methods

2.1. Study Design, Setting, and Period

This study was performed in Hiwot Fana Specialized University Hospital, found in Harar town, Eastern Ethiopia. Harar is located 510 km east of the capital city of Ethiopia, Addis Ababa, from 8th February–8th March, 2021.

2.2. Study Design

Hospital‐based cross‐sectional study was conducted.

2.2.1. Population

Source population: all patients with type two DM who are on follow up at HFSUH were the source population.

Study population: Adult type two DM patients' age ≥18 years who were attending the diabetic unit in HFSUH during the study period and on anti‐diabetic medication were the study population.

2.3. Inclusion and Exclusion Criteria

2.3.1. Inclusion Criteria

All adult (18 years and above) type 2 diabetic patients for the last six or more months and attending follow up clinic during study period.

2.3.2. Exclusion Criteria

Patients who were critically ill and not volunteer to participate were excluded.

2.3.3. Sample Size and Sampling Technique

The sample size was calculated using a single population proportion formula designated as n = $\frac{{\mathit{Za}/2}^2\mathit{p}(1-p)}{d^2}$ based on the assumption of p = 0.189, which was the proportion of diabetic retinopathy in Debre Markos Referral Hospital, Northwest Ethiopia [21], a 95% confidence level, 5% margin of error (d). Since the population size in the study area is less than 10,000, the final sample size was estimated using the correction formula nf = $\frac{\mathit{ni}}{1+\frac{\mathit{ni}}{N}}$.

$$n=\frac{{\mathit{Za}/2}^{2}p(1-p)}{d^2}=\frac{{(1.96}^2\left)0.189\right(1-0.189)}{{0.05}^2}$$

$$\mathit{\text{nf}}=\frac{\mathit{ni}}{1+\frac{\mathit{ni}}{N}}=\frac{236}{1+\frac{236}{1000}}=191+10\%=210$$

n = estimated sample size,

P = anticipated proportion of diabetic retinopathy 18.9%, taken from a study conducted in Debre Markos Referral Hospital, Northwest Ethiopia [21],

Zα/2 = value of the standard normal distribution (Z‐statistic) at the 95% confidence level (α = 0.05) which is 1.96,

d = margin of error 5% (0.05);

10% = a contingency for incomplete data.

The final sample size obtained including a 10% non‐response rate was 210.

The study population was enrolled from the list of outpatients attending the diabetic unit in HFSUH using a systematic sampling method. The kth value in the systematic sampling procedure was calculated by dividing the source population by the total sample size. The kth value was calculated based on the source population monthly attended in the diabetic unit of HFSUH (four hundred monthly attended type two diabetic patients).

Resulting in a sampling interval of k = 400/210, the kth value for T2DM was 2 from the list of 1–2 T2DM patients. The first patient was selected by using a lottery method, then data were collected from every second patient starting from the first patient selected by the lottery method, and continued until the desired sample size was obtained. The patient registry was used as a sampling frame.

2.3.4. Data Processing and Analysis

The data collection tool was adopted and modified by reviewing different literature which were designed to seek information pertaining to socio demographic factors, clinical factors, treatment modality, behavioral factors and diabetic care and through guideline for screening diabetic retinopathy [13]. Data was collected using semi‐structured questionnaire and Slit‐Lamp bio‐microscopy examination. Content validity was assessed by one ophthalmologist and one adult health nurse specialist. We had conducted a pre‐test among 5% of total sample size at Jogla Hospital, and necessary wording and format adjustments were made. Internal consistency for key multi‐item sections achieved a Cronbach's alpha of (0.82). Multicollinearity was assessed using the variance inflation factor (VIF). Variables with VIF > 10 were considered indicative of multicollinearity. No significant multicollinearity was detected among independent variables.

2.4. Operational Definitions

Diabetic retinopathy is considered when the presence of any characteristic lesions of the following is detected: micro aneurysms, hemorrhage, hard exudates, cotton‐wool spots, retinal vein beading changes, microvascular abnormalities in the retina, and/or neovascularization lesions on fundus images [22].

Non‐proliferative diabetic retinopathy (NPDR): the presence of micro aneurysm without any formation of abnormal new blood vessels on retinal camera examination [23], which is classified as mild NDPR, moderate NDPR, and severe NDPR.

Mild NPDR: the presence of microaneurysms only on retinal camera examination.

Moderate NPDR: the presence of microaneurysms on retinal camera examination and other signs (e.g., dot and blot hemorrhages, hard exudates, cotton wool spots), but less than severe NPDR.

Severe NPDR: presence of moderate NPDR with any of the following: intraretinal hemorrhages ( ≥ 20 in each quadrant), definite venous beading (in two quadrants), intraretinal microvascular abnormalities (in one quadrant), and no signs of proliferative retinopathy.

Proliferative diabetic retinopathy (PDR): the presence of severe NPDR and one or more of the following on retinal camera examination: neovascularization, vitreous/preretinal hemorrhage [23].

Physical activity was defined in the following ways [24]:

Physical inactivity: anyone who does not perform any form of physical activity for at least 10 min per day.

Low physical activity: anyone who performs activities (walking, running, or cycling) less than 5 days for at least 30 min per day or vigorous intensity activities (like carrying or lifting heavy loads or digging) less than 3 days for at least 20 min per day.

Moderate physical activity: anyone who performs moderate activity for more than 5 days for at least 30 min per day or vigorous intensity activity more than 3 days for at least 20 min per day.

Alcohol consumption was defined based on the National Institute on Alcohol Abuse and Alcoholism [15], as follows:

Nondrinkers (abstainers, or no alcohol consumption history), moderate drinkers (up to one drink/day for women and up to two drinks/day for men), and heavy drinkers ( > 1 drink/day for women and > 2 drinks/day for men).

2.5. Data Processing and Analysis

Data was coded, entered, and cleaned using Epi Data version 3.1 software. Double entry was made to cross‐check the data for completeness before analysis. The entered data were exported and analyzed with the Statistical Package for Social Science (SPSS) version 20 software.

Descriptive statistics were performed to identify the distribution of socio‐demographic characteristics of the study participants. Bivariate logistic regression was used to assess the association between dependent and independent variables. To control confounding effects, those variables having p value of < 0.25 were included in the multi‐variable analysis. The level of statistical significance was declared for a variable having p value < 0.05.

3. Results

3.1. Socio‐Demographic Characteristics of the Participants

A total of 210 adult type 2 DM patients who attended the diabetic unit at HFSUH were included in this study making a response rate of 100%. Of these, more than half (53.8% and 53.3%) were female and less than 60 years old, respectively. Regarding their marital status, around three‐quarters (78.1%) were married, whereas 20 (9.5%) were never married. The mean age (± standard deviation) of participants was 46.7 ± 12.7 years. Nearly two‐third (61.4%) were urban dwellers. One‐third (32.9%) were government employees, more than half (58.6%) had completed college education (Table 1).

Table 1.

Socio‐demographic characteristics of type two DM patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

Variable	Category	Diabetic retinopathy N (%)
		Yes N (%)	No N (%)
Sex	Male	41 (19.5)	56 (26.7)
	Female	17 (8.1)	96 (45.7)
Age	< 60 years	13 (6.2)	99 (47.1)
	≥ 60 years	45 (21.43)	53 (25.24)
Monthly income	Less than 3700	39 (18.6)	108 (51.4)
	Greater than 3700	19 (9)	44 (21)
Residence	Urban	34 (16.2)	95 (45.2)
	Rural	24 (11.43)	57 (27.14)
Occupation	Government employee	14 (6.7)	55 (26.2)
	Daily laborer	17 (8.1)	33 (15.7)
	Merchant	12 (5.7)	22 (10.5)
	Farmer	15 (7.14)	41(19.52)
	Student	0	1 (0.5)
Marital status	Single	2 (0.95)	18 (8.6)
	Married	50 (23.8)	114 (54.3)
	Divorced	6 (2.9)	14 (6.6)
	Widowed	0	6 (2.9)
Educational status	Unable to read and write	10 (4.8)	9 (4.3)
	Primary school	2 (0.95)	9 (4.3)
	Secondary school	21 (10)	36 (17.1)
	College and above	25 (11.9)	98 (46.7)

3.2. Clinical Factors of Participants

Regarding duration of diabetes mellitus, 121 (57.6%) had a diabetic duration of less than 5 years, whereas the remaining 89 (42.4%) had a diabetic duration of 5 years and above. One‐third (31%) of participants had a history of hypertension. Less than one‐tenth (5.7%) of participants were diagnosed as having micro‐vascular complications of both renal and heart disease.

Mean fasting blood glucose was 185.1 ± 75 mg/dL, and more than half (51.9%) of participants had seven and above glycemic control. More than half (57.1%) of the participants had a body mass index (BMI) of 18.5–25 kg/m². Whereas, 41% of them had a body mass index of greater than 25 kg/m². Near to half (44.8%) of participants had a family history of DM, and only 41 (19.5%) of them had developed DR (Table 2).

Table 2.

Clinical factors of type two diabetic patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

Variable	Category	Diabetic retinopathy N (%)
		Yes (%)	No (%)
Hypertension	Yes	37 (17.6)	28 (13.3)
	No	21 (10)	124 (59)
Duration of DM in (years)	< 5 years	8 (3.8)	113 (53.8)
	≥ 5 years	50 (23.8)	39 (18.6)
CKD	Yes	4 (1.9)	8 (3.8)
	No	54 (25.7)	144 (68.6)
Chronic cardiac illness	Yes	0	12 (5.7)
	No	58 (27.6)	140 (66.7)
Family history of DM	Yes	41 (19.52)	53 (25.24)
	No	17 (8.1)	99 (47.1)
HbA1C	< 7	5 (2.4)	96 (45.7)
	≥ 7	53 (25.2)	56 (26.7)
Body mass index	< 18.5 kg/m2	0	4 (1.9)
	18.5–25 kg/m2	20 (9.5)	100 (47.6)
	> 25 kg/m2	38 (18.1)	48 (22.9)

3.3. Behavioral Factors of Participants

More than one‐third (42.4%) of participants had performed moderate physical activity. But 79 (37.6%) of the participants performed low physical activity. One hundred ninety‐one (91.4%) of the participants were nondrinkers (Table 3).

Table 3.

Behavioral factors of type two diabetic patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

Variable	Category	Diabetic retinopathy N (%)
		Yes (%)	No (%)
Drinking status	Non drinkers	52 (24.8)	140 (66.7)
	Moderate drinkers	1 (0.5)	6 (2.9)
	Heavy drinkers	5 (2.3)	6 (2.9)
Physical activity	Physically inactive	14 (6.7)	28 (13.3)
	Low physical activity	18 (8.6)	61 (29)
	Moderate physical activity	26 (12.4)	63 (30)

3.4. Diabetic Care‐Related Factors of Participants

Among study participants, half (49%) of them were visiting health institution every 3 months for DM follow up, whereas more than one‐fourth (28.6%) of them were visiting health institution every 1 month and nearly one‐fourth (22.4%) were visiting health institution every 2 months. More than one‐fourth (27.1%) of participants had a history of dilated eye checkup, whereas the remaining three‐quarters (72.8%) of participants had no checkup. A total of 133 (63.3%) did not attend diabetic health education, which is given in the hospital, whereas the remaining about one‐third (36.4%) of them attended diabetic health education given in the hospital (Table 4).

Table 4.

Diabetic care‐related factors of type two diabetic patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

Variable	Category	Diabetic retinopathy		Total (%)
		Yes (%)	No (%)
History of dilated eye check‐up	Yes	12 (5.7	45 (21.4)	57 (27.1)
	No	45 (21.4)	108 (51.4)	153 (72.8)
Health education about DM	Yes	8 (3.8)	69 (32.9)	77 (36.7)
	No	50 (23.8)	83 (39.5)	133 (63.3)
Follow‐up frequency	Every month	8 (3.8)	52 (24.8)	60 (28.6)
	Every two months	19 (9.1)	28 (13.3)	47 (22.4)
	Every three months	31 (14.8)	72 (34.3)	103 (49)

3.5. Treatment Modality of the Participants

Concerning treatment modality, more than one third (38.6%) of participants used insulin alone, whereas nearly a quarter (22.4%) of participants used oral anti‐glycemic agents (Figure 1).

Figure 1.

Modality of treatment of type two diabetic patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

3.6. Prevalence of Diabetic Retinopathy Among Adult Type Two Diabetes Mellitus Patients

In the current study, 58 (27.6%) of the study participants had DR (Figure 2). Among those who had DR, three‐quarter (72.4%) of the participants had mild NPDR, one‐fourth (22.4%) had moderate NPDR and less than one‐tenth (3.4%, 1.7%) had severe NPDR and PDR, respectively (Table 5).

Figure 2.

Prevalence of diabetic retinopathy among adult type two diabetes mellitus patients at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021.

Table 5.

The prevalence of classification of diabetic retinopathy in the affected eye among adult type two diabetes mellitus patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia, 2021 (n = 210).

Diabetic Retinopathy	Frequency	Percent
1. Normal (no DR)	152	72.38
2. Mild NPDR	42	20
3. Moderate NPDR	13	6.19
4. Severe NPDR	2	0.95
5. PDR	1	0.48
Total	210	100%

3.7. Factors Associated With Diabetic Retinopathy Among Type Two DM Patients

To identify factors associated with diabetic retinopathy among type two DM patients, a logistic regression model was fitted. The variables with p < 0.25 in bivariate analysis were included in the multivariable model to prevent exclusion of potential confounders, following the recommendations of Hosmer and Lemeshow.

In bivariate analysis, sex, mode of treatment, comorbid hypertension, fasting blood glucose, family history of DM, age, duration of DM illness, glycemic control, educational status of respondent, body mass index, number of health institution visit were significantly associated with DR. Finally, after obtaining statistically significant variables at p < 0.25 in binary logistic regression analysis, multiple logistic regression analysis was carried out to see the independent predictors of diabetic retinopathy.

The multivariable logistic regression was carried out by taking diabetic retinopathy as a covariate in addition to those variables for which a significant association was obtained in binary logistic regression. After adjusting for potential confounders, comorbid hypertension, duration of DM illness, having a family history of DM, age, and HbA1c were independent predictors of DR. However, the mode of treatment, fasting blood glucose, sex, educational status of participants, body mass index, and number of health institution visits lost their significance (Table 6).

Table 6.

Bivariate and multivariable logistic regression analysis of DR among adult type two DM patients at Hiwot Fana specialized university hospital, Harar, Ethiopia,2021 (n = 210).

Variable	Category	Diabetic retinopathy		COR (95% CI)	AOR (95% CI)	p value
		Yes (%)	No (%)
Sex	Male	41 (19.5)	56 (26.7)	4.13 (2.15, 7.96)	2.134 (0.7, 6.51)	0.183
	Female	17 (8.1)	96 (45.7)	1	1
Age	< 60 years	13 (6.2)	99 (47.1)	0.16 (0.08, 0.31)	0.28 (0.09,0.84)	0.023*
	≥ 60 years	45(21.43)	53 (25.24)	1	1
Hypertension	Yes	37 (17.6)	28 (13.3)	7.803 (3.98, 15.32)	8.63 (2.51, 29.75)	0.001*
	No	21 (10)	124 (59)	1	1
Follow‐up frequency	Every month	8 (3.8)	52 (24.8)	0.36 (0.15, 0.84)	0.48 (0.09, 2.28)	0.099
	Every two months	19 (9.1)	28 (13.3)	1.58 (0.77, 3.23)	1.83 (0.49,6.75)	0.494
	Every three months	31 (14.8)	72 (34.3)	1	1
Duration of DM in (years)	< 5 years	8 (3.8)	113 (53.8)	0.06 (0.02, 0.13)	0.184 (0.06, 0.61)	0.006*
	≥ 5 years	50 (23.8)	39 (18.6)	1	1
Mode of treatment	Insulin alone	21(10)	60 (28.6)	1.34 (0.65,2.78)	1.71(0.45, 6.46)	0.428
	Oral antiglycemic	20 (9.5)	27 (12.9)	2.83 (1.29, 6.22)	3.59 (0.79,16.25)	0.098
	Combined	17 (8)	65 (31)	1	1
HbA1C	< 7	5 (2.4)	96 (45.7)	0.06 (0.02, 0.15)	0.06 (0.013,0.283)	0.000*
	≥ 7	53 (25.2)	56 (26.7)	1	1
FBS				1.004 (1.00, 1.01)	1.003 (0.996,1.011)	0.386
Body mass index	< 18.5 kg/m2	0	4 (1.9)			0.999
	18.5 25 kg/m2	20 (9.5)	100 (47.6)	0.25 (0.13,0.48)	0.998 (0.316,3.154)	0.997
	> 25 kg/m2	38 (18.1)	48 (22.9)	1	1
Family history of DM	Yes	41(19.52)	53 (25.24)	4.51 (2.34,8.69)	3.29 (1.02, 10.67)	0.047*
	No	17 (8.1)	99 (47.1)	1	1
Educational status	Unable to read and write	10 (4.8)	9 (4.3)	4.37 (1.59,11.86)	1.66 (0.26,10.78)	0.597
	Primary	2 (0.95)	9 (4.3)	0.87 (0.18,4.29)	1.77 (0.104, 3.002)	0.692
	Secondary	21 (10)	36 (17.1)	2.29 (1.14, 4.58)	0.45 (1.62 0.46)	0.453
	College and above	25 (11.9)	98 (46.7)	1	1

Abbreviations: AOR, adjusted odds ratio; CCI, confidence interval; COR, crude odds ratio; FBS, fasting blood sugar; HbAlc, hemoglobin A1c.

^* p value < 0.05.

4. Discussion

The current study aimed to explore the prevalence of diabetic retinopathy and its associated factors among type two DM patients who attended the diabetic unit at Hiwot Fana specialized university hospital, Harar, Ethiopia. The prevalence of DR was 27.6% with 95% CI (22%–34%). Being less than 60 years old (AOR = 0.28, 95% CI: 0.09, 0.84), having comorbid hypertension (AOR = 8.63, 95% CI: 2.51, 29.75), glycemic control less than seven (AOR = 0.06, 95% CI: 0.01, 0.28), having family history of DM (AOR = 3.29, 95% CI: 1.02, 10.67), less than 5 years' diabetes duration (AOR = 0.18, 95% CI: 0.06, 0.61) were factors significantly associated with diabetic retinopathy.

According to this study, the prevalence of DR among type two diabetes patients was in line with a study conducted in the US (28.5%) [16], Asia (28%) [17], and Nigeria 26.2% [25]. However, it is higher than study conducted in, US (9.1%) [26], North East Poland (23.04%) [27], Spain (14.9%) [28], Denmark(21.2%) [29], Rural Southern China (18.2%) [30], Beijing, China (8.1%) [31], Taify City (16%) [32], Debre Markos Referral Hospital (18.9%) [21], Arbaminch General hospital 13% [33]. The possible explanation for this variation might be due to the differences in the Study period, health‐seeking behavior among the respondent, study area, diagnostic methods, discrepancy in self‐care practice might be possible explanations for this discrepancy of the prevalence of diabetic retinopathy among type two DM patients. On the other hand, this study is lower than study conducted in Armenia (36.1%) [34], Iran (45.1%) [35], Pakistan (42.86%) [36], Zambia (52%) [37], Egypt (34.6%) [38], Sudan (82.6%) [39], Jimma university hospital, Ethiopia (41.4%) [40], Tikur Anbesa specialized hospital, Addis Ababa, Ethiopia (51.3%) [19]. The possible reason may be due to a difference in methodology, sample size, and study population.

The result of the multivariate logistic regression model indicated that HbAlc level, age, having a family history of diabetes mellitus, comorbid hypertension, and duration of diabetes illness were significantly associated with DR. In this study, type two diabetes patients with a history of comorbid hypertension had about nine times higher odds for diabetic retinopathy (AOR = 8.63, 95% CI: 2.51, 29.75) as compared to type two diabetes patients without a history of comorbid hypertension which is in line with the study conducted in Western India [41], Nepal [42], Indonesia [43], Sudan [39], Zambia [37], Tikur Anbessa specialized hospital [19], Debre Markos referral hospital [21]. However, it is inconsistent with the study conducted in India [44] and Iran [45]. This inconsistency might be due to the difference in the sample size, study period, health‐seeking behavior among the respondents, study area, diagnostic method, and different levels of understanding in self‐care practice. Other possible explanations for such results might be due to hypertension upregulating the expression of vascular endothelial growth factor (VEGF) in retinal endothelial cells and ocular fluids, which can promote DR. The association between HbAlc level and DR aligns with established mechanisms, such as accumulation of advanced glycation end products and VEGF‐mediated neovascularization in chronically hyperglycemic states. These pathways likely explain the higher DR prevalence observed in participants with elevated fasting blood glucose [46].

The present study demonstrated that those patients who had a family history of DM were three times more likely to develop diabetic retinopathy as compared to patients who did not have a family history of DM (AOR = 3.29, 95% CI: 1.02, 10.67). This finding is in agreement with a study conducted in Iran [45] and Jimma, Ethiopia [47]. The current study revealed that the likelihood of developing DR was decreased by 82% (AOR = 0.18, 95% CI: 0.06, 0.61) among type 2 DM patients whose duration of DM illness was less than 5 years compared to those whose duration of DM was 5 years and above, while adjusting for other variables in the model. The result of this study is in line with study conducted in Denmark [29], Spain [28], Southern China [30], Korean [48], Armenia [34], Indonesia [43], Iran [45], Southern Iran [49], Nepal [42], Sudan [50], Zambia [37], Tanzania [51], Debre Markos University Hospital [21], Jimma Specialized University Hospital [40]. However, it is inconsistent with a study conducted in India [44] and Iran [35]. The possible explanation for this discrepancy might be due to the variation in the lifestyle of participants, variation in awareness regarding health‐seeking behavior, and sample size.

However, a possible reason for this result might be due to the duration of diabetes illness increases the exposure of the retina to hyperglycemia gives rise to the accumulation of advanced glycation end products that play a tremendous role in retinopathy, additionally advanced glycation end products may increase procoagulant activity, vascular permeability, adhesion molecule expression, and monocyte influx actions that may cause vascular injury [52].

The odds of developing DR were decreased by 72% (AOR = 0.28, 95% CI: 0.09, 0.84) among type 2 DM patients aged less than 60 years as compared to those aged 60 and above, while adjusting for other variables in the model. This finding is consistent with studies conducted in India [44], Jimma, Ethiopia [47], and Iran [45]. The apparent protective effect of younger age may reflect survival bias, whereby individuals with severe microvascular complications are overrepresented at older ages.

Additionally, older adults may have experienced prolonged periods of undiagnosed or poorly controlled diabetes before initiation of care, contributing to cumulative retinal damage. Younger patients may also have shorter disease duration and improved adherence following a recent diagnosis. The possible explanation for this finding might be due to the retinal vessel density decreasing during aging [53]. The current study showed that participants with HbAlc less than 7% were about 94% less likely (AOR = 0.06, 95% CI: 0.01, 0.28) to have diabetic retinopathy as compared to those who had HbA1c 7% and above. This finding is consistent with studies conducted in the US [16], Denmark [29], Spain [28], Korea [48], Iran [45], and Tikur Anbesa Specialized Hospital [19].

Similarly, the study conducted at Jimma University Hospital revealed that the likelihood of developing DR was nine times higher in diabetic patients with poor glycemic control as compared to those with good glycemic control [47]. Additionally, a study conducted in Debre Markos Referral Hospital revealed that the odds of developing DR among diabetic patients with poor glycemic control were five times higher than those with good glycemic control [21]. The possible explanation for this result might be that poor glycemic control causes the retinal vasculature to suffer a progressive dysfunction, retinal mitochondria become dysfunctional, and levels of superoxide species upsurge, which eventually accelerates cytochrome c release, capillary cell apoptosis, and DNA damage [54].

5. Conclusion

This study revealed a high prevalence of diabetic retinopathy among T2DM patients in Eastern Ethiopia. Key associated factors included duration of diabetes, older age and poor glycemic control. These findings highlight the urgent need for routine ophthalmologic screening and targeted diabetes education in this population.

Author Contributions

F.A., Y.T., D.G., E.Z., and K.T. were involved in the design of the study, data analysis, interpretation of the findings, report writing, and manuscript preparation of this study. F.A., Y.T., D.G., E.Z., and K.T. were involved in the conception, study design, execution, acquisition of data, analysis, and interpretation, or in all these areas by revising, editing, and supervising up to final manuscript preparation.

Funding

The authors have nothing to report.

Ethics Statement

Prior to the commencement of data collection, ethical clearance and approval were obtained from the Institutional Review Board (IRB) of the College of Health Sciences of Addis Ababa University. An official letter was obtained from the School of Nursing and Midwifery, Department of Nursing (Reference number: CHS/NSG/00/59).

Consent

The study participants were informed about their rights to refuse, to join, ask any questions, or withdraw at any time during the data collection process without any fear. After explaining the purpose and possible benefit of the study, oral and written informed consent were obtained from each patient before starting the interview. The information of the participants was kept confidential.

Conflicts of Interest

The authors declare no conflicts of interest.

Strengths and Limitations

This study was conducted to assess the prevalence of diabetic retinopathy and its associated factors among type two DM patients at Hiwot Fana Specialized University Hospital. There are important strengths of this study. Primarily, in this study, 100% of the response rate was included, and a face‐to‐face interview was used, which prevents ambiguity, for data completeness, and minimizes a certain sort of recall bias. On the other hand, the use of a cross‐sectional design also provided a sufficiently large sample size, and it may include different independent variables. As a matter of fact, this study was not without limitations. By its definition, cross‐sectional studies are difficult to draw a cause‐and‐effect relationship between associated factors and the dependent variable.

Transparency Statement

The lead author, Fekadu Abera Kebede, affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Data Availability Statement

The data used during the current study are available from the corresponding author upon reasonable request.