European Journal of Cardiovascular Medicine

Diabetic retinopathy is a microvascular complication of diabetes that can lead to irreversible vision loss if left untreated. Poor glycemic control, as reflected by elevated HbA1c levels, is a well-documented risk factor for the development and progression of DR. However, the precise correlation between HbA1c levels and the severity of DR remains an area of active investigation. This study seeks to evaluate this relationship by assessing HbA1c levels in patients with varying stages of DR.

• Study Design: Cross-sectional study
• Duration: 1 year
• Study Population: Patients diagnosed with T2DM attending an endocrinology or ophthalmology clinic

• Inclusion Criteria:
• Diagnosed cases of T2DM for at least 5 years
• Age between 40-75 years
• Availability of recent HbA1c test results (within 3 months)

• Exclusion Criteria:
• Presence of other retinal disorders (e.g., hypertensive retinopathy, macular degeneration)
• History of ocular surgery or laser treatment for DR
• Uncontrolled hypertension or kidney disease affecting microvascular outcomes

• Data Collection:
• HbA1c levels measured through standard laboratory procedures
• Diabetic retinopathy staging based on ETDRS (Early Treatment Diabetic Retinopathy Study) classification via fundoscopic examination
• Classification into No DR, Mild NPDR, Moderate NPDR, Severe NPDR, and PDR (Proliferative DR)

• Statistical Analysis:
• Mean HbA1c levels compared across DR severity groups
• Pearson’s correlation coefficient to assess strength of association
• Logistic regression to determine independent risk factors.

• Patients with no DR expected to have significantly lower mean HbA1c levels compared to those with NPDR or PDR.
• A positive correlation anticipated between increasing HbA1c levels and severity of DR.
• HbA1c > 8% may be associated with a higher likelihood of developing advanced DR.
• Additional risk factors (e.g., duration of diabetes, hypertension, lipid profile) may influence DR severity.

Table 1 Patient Demographics and Baseline Characteristics

Table 2 Distribution of Patients by Diabetic Retinopathy (DR) Stages

Table 3 Mean HbA1c Levels by DR Stage

Table 4Correlation Between HbA1c and DR Severity

Table 5 Multivariate Analysis of Risk Factors for DR

1. Patient Demographics and Baseline Characteristics

• The mean age of patients was 55.4 years, with a balanced gender distribution (55% male, 45% female).
• The average duration of diabetes was 10.2 years, suggesting that chronic hyperglycemia plays a role in DR development.
• 60% of patients had hypertension, and 45% had dyslipidemia, indicating that these comorbidities may contribute to microvascular complications like DR.
• The mean BMI was 27.5 kg/m², suggesting a trend toward overweight/obesity, which may further impact glycemic control.

2. Distribution of Patients by Diabetic Retinopathy (DR) Stages

• 40% of patients had no DR, while 60% had some form of DR, indicating a high prevalence of DR among diabetics.
• 25% had mild NPDR, while 35% had moderate to severe NPDR or PDR, highlighting the importance of early detection.
• The prevalence of PDR (7.5%) suggests that a subset of patients has progressed to sight-threatening stages.

3. Mean HbA1c Levels by DR Stage

• A clear trend was observed: increasing HbA1c levels were associated with more severe DR.
• Patients with no DR had a mean HbA1c of 6.5%, which is within the recommended range.
• Mild NPDR patients had an HbA1c of 7.2%, indicating early signs of glycemic dysregulation.
• Moderate to severe NPDR and PDR had mean HbA1c levels of 8.1%, 9.0%, and 9.8% respectively.
• Inference: Higher HbA1c levels significantly increase the risk of DR progression (p-values <0.05 to <0.001).

4. Correlation Between HbA1c and DR Severity

• A moderate to strong positive correlation (r = 0.68, p < 0.001) between HbA1c and DR severity confirms that poor glycemic control is a major determinant of DR progression.
• Clinical implication: Maintaining HbA1c below 7% can significantly reduce the risk of severe DR.

5. Multivariate Analysis of Risk Factors for DR

• HbA1c (%) had the highest odds ratio (OR = 2.5, p < 0.001), making it the strongest predictor of DR.
• Duration of diabetes (OR = 1.8, p < 0.01) was also a significant risk factor, reinforcing that longer exposure to hyperglycemia increases DR risk.
• Hypertension (OR = 1.6, p < 0.05) and dyslipidemia (OR = 1.4, p < 0.05) were moderate risk factors, indicating the role of vascular dysfunction.
• BMI (OR = 1.2, p = 0.08) was not statistically significant, suggesting that obesity alone may not be a direct risk factor unless accompanied by poor glycemic control.

Key Takeaways

1. HbA1c is a strong predictor of DR severity – higher levels are significantly associated with worsening DR stages.
2. Strict glycemic control (HbA1c <7%) can help prevent or slow DR progression.
3. Other risk factors like hypertension and dyslipidemia should be managed alongside diabetes to reduce DR risk.
4. Regular screening is essential for early detection and intervention, especially in patients with long-standing diabetes.

Our study investigates the association between glycated hemoglobin (HbA1c) levels and the presence and severity of diabetic retinopathy (DR) in patients with Type II Diabetes Mellitus (T2DM). The findings indicate a significant correlation between elevated HbA1c levels and the progression of DR. This section compares our results with those of ten other studies to contextualize our findings within the broader body of research.

1. Alghadyan et al. (2011): In a study conducted in Saudi Arabia, the prevalence of DR was found to be 36.1%. The researchers identified a significant association between higher HbA1c levels and the development of DR, aligning with our findings that poor glycemic control is a critical risk factor.
2. Hajar et al. (2015): This study reported a DR prevalence of 27.8% among diabetic patients. The authors concluded that elevated HbA1c levels were significantly associated with the presence of DR, supporting the notion that maintaining lower HbA1c levels may reduce DR risk.
3. El-Bab et al. (2012): Investigating DR prevalence in Medina, the study found a rate of 36.4%. A significant relationship between higher HbA1c levels and DR severity was observed, corroborating our results that suggest a positive correlation between HbA1c and DR progression.
4. Khan et al. (2016): In a cross-sectional study, the prevalence of DR was 14.8%. The researchers identified HbA1c as a significant predictor of DR, emphasizing the importance of glycemic control in preventing retinal complications.
5. Yau et al. (2012): This global meta-analysis reported a DR prevalence of 34.6% among diabetic individuals. The study highlighted that higher HbA1c levels were associated with increased DR risk, consistent with our findings.
6. Klein et al. (1984): The Wisconsin Epidemiologic Study of Diabetic Retinopathy found that higher HbA1c levels were significantly associated with the incidence and progression of DR, reinforcing the link between glycemic control and retinal health.
7. UK Prospective Diabetes Study (1998): This landmark study demonstrated that intensive blood-glucose control reduced the risk of microvascular complications, including DR, underscoring the importance of maintaining lower HbA1c levels.
8. Diabetes Control and Complications Trial (1993): The DCCT established that intensive diabetes therapy aimed at achieving near-normal HbA1c levels significantly reduced the development and progression of DR in patients with type 1 diabetes, findings that are applicable to type 2 diabetes as well.
9. Kohner et al. (1998): The EURODIAB IDDM Complications Study reported that higher HbA1c levels were associated with an increased prevalence of DR, highlighting the role of glycemic control in managing DR risk.
10. Wong et al. (2009): This study found that each 1% increase in HbA1c was associated with a 14% increase in the risk of DR, further supporting the association between higher HbA1c levels and DR development.

Collectively, these studies corroborate our findings that elevated HbA1c levels are significantly associated with both the presence and severity of DR in patients with T2DM. The consistency across diverse populations and study designs strengthens the evidence that maintaining optimal glycemic control is crucial in preventing the onset and progression of DR.

However, it is important to note that while HbA1c is a significant predictor, other factors such as the duration of diabetes, hypertension, and dyslipidemia also contribute to DR risk. Comprehensive management of these factors, alongside regular ophthalmologic screenings, is essential for effective prevention and early detection of DR.

In conclusion, our study aligns with existing literature emphasizing the critical role of glycemic control in managing DR risk. Future research should focus on longitudinal studies to further elucidate the causal relationships and explore the impact of multifactorial interventions on DR outcomes. 

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