The association between HBA1C level and the outcome of hernia surgery in diabetic patients managed at a tertiary center: A retrospective cohort study

Introduction

Hernia is a prevalent condition worldwide, with an estimated 20 million hernia repair surgeries performed annually and a 2% lifetime risk of abdominal wall hernia development in men.^1,2 A 2016 systematic review titled “Diabetes and Risk of Surgical Site Infection” reported an increased risk of surgical site infections across most types of surgeries among diabetic patients, excluding obstetrical and gynecological procedures.³ Additionally, a study conducted at the Department of Surgery, Mount Sinai Beth Israel, United States, involving 2,200 patients divided into two groups based on their HbA1C levels, found that elevated HbA1C (>6.5%) combined with dirty wounds or advanced age significantly increased the likelihood of postoperative infections.⁴ Despite these findings, there is limited research on the relationship between HbA1C levels and the risk of infection or complications following hernioplasty, both globally and in Saudi Arabia. This retrospective study aims to investigate the association between HbA1C levels and hernia surgery outcomes in diabetic patients treated at a tertiary hospital

Methods

A retrospective study was conducted in the Department of Surgery at King Abdulaziz Medical City (KAMC), under the Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia, from September 2017 to September 2022. The study received approval from the Institutional Review Board of the King Abdullah International Medical Research Center (KAIMRC).

It included young and adult diabetic patients, encompassing those with uncontrolled diabetes mellitus (HbA1C ≥ 7%) and those with controlled diabetes mellitus (HbA1C < 7%) as a comparison group, who underwent hernioplasty surgery and met the eligibility criteria. The study involved patients of both genders, aged 20 to 85 years, who underwent hernioplasty via open or laparoscopic techniques, with or without mesh, and received treatment at KAMC. The exclusion criteria included patients undergoing long-term steroid therapy and those receiving chemotherapy within six months prior to surgery. A formal sample size calculation was not required, as all cases meeting the study’s case definition during the specified period were considered for inclusion.

Data from 301 patients were retrieved from the “BESTcare” healthcare database (https://ngha.med.sa/English/AboutNGHA). Of these, only 140 patients fulfilled the inclusion and exclusion criteria. Patients who failed to meet the eligibility requirements, including those without recorded HbA1C levels, were excluded. The collected data were transferred to an Excel sheet for review, selection, and analysis by the research team. The dataset included demographic information (age, gender, preoperative BMI), surgical complications (postoperative wound infection, postoperative abscess, recurrence), diabetic complications, laboratory parameters (hemoglobin level, preoperative HbA1C level), the type of hernioplasty surgery (open vs. laparoscopic procedures), and diagnoses of comorbid conditions such as cardiovascular diseases, hypertension (HTN), chronic kidney disease (CKD), liver disease, or lung disease.

Recurrence was defined as a diagnosis made by a physician and documented in the healthcare system records (BestCare). Wound infection was identified based on the definition provided by the Centers for Disease Control and Prevention (CDC). Although HbA1C levels were measured preoperatively, postoperatively, and during follow-up, the statistical analysis primarily focused on preoperative HbA1C levels. This decision was made because there were no significant variations among the three measurements that would affect the results.

Statistical analysis and data management were performed using SPSS software, version 26 for Windows. Descriptive statistics were employed to summarize the dataset. Continuous variables were presented as medians with interquartile ranges, while categorical variables were reported as frequencies (n) and percentages (%). The Student's t-test was utilized to compare continuous variables, and categorical variables were analyzed using the Chi-square test or Fisher's exact test. Binary logistic regression was applied to assess the association between preoperative HbA1C (categorized) and outcomes, including wound infection and recurrence. All statistical tests were two-sided, with a significance level set at p < 0.05.

Patient confidentiality and anonymity were strictly maintained by excluding identifiers from the dataset. All data, both electronic and physical, were securely stored within the MNGHA premises and were accessible only to the research team. The STROBE checklist has been utalized to adhere to international guidelines for reporting retrospective studies.²⁰ Furthermore, the collected data has also been made available in the repository.²⁰

Results

This study initially included 147 diabetic patients who underwent hernia surgery at the Ministry of National Guard Health Affairs (MNGHA) in Riyadh between 2017 and 2022. However, due to missing data in some cases, the final analysis was conducted on 140 patients who met the inclusion criteria with complete data. The gender distribution was nearly equal, with males comprising 52.1% (n=73) and females 47.9% (n=67). Most patients were aged between 47 and 69 years, with a mean age of 58 years and a median age of 57 years (IQR = 14). Regarding preoperative BMI, the majority of patients were classified as obese, with a median BMI of 31.215 (IQR = 9.04). Approximately one-third of the patients 27.14% (n=38) underwent open hernia repair, while the remaining 72.86% (n=102) underwent laparoscopic repair. Recurrence occurred in 21 patients (15%) within one year post-surgery, and 7 patients (5%) developed postoperative wound infections. Preoperative HbA1C values were recorded, revealing that 91 patients had uncontrolled HbA1C levels (≥7%). Additionally, 10 patients (7.14%) were diagnosed with chronic kidney disease, and 84 patients (60%) had hypertension ( Table 1).

A statistically significant difference was found between hypertensive patients and the uncontrolled HbA1C group (p = 0.039), with hypertension (HTN) being more common in the group with HbA1C ≥ 7% ( Table 1). The incidence of wound infection was 5 cases among patients with uncontrolled HbA1C and 2 cases in the controlled HbA1C group, with no statistically significant difference between the groups (OR 0.706; 95% CI 0.132–3.784; p = 0.706). Similarly, no significant difference was observed between the two groups for hernia recurrence, with 11 (22.44%) cases of recurrence in the controlled HbA1C group and 10 (10.99%) cases in the uncontrolled HbA1C group (OR 2.345; 95% CI 0.917–5.997; p = 0.075) ( Table 2).

Discussion

The results of this retrospective study indicate that there is no significant association between different HbA1C levels, whether controlled or uncontrolled, and the outcomes of hernia surgery in diabetic patients. However, a significant relationship was observed between hypertension and wound infection in the exposed group. In Saudi Arabia, hernia is a prevalent condition affecting both male and female adults.⁵ A 2017 cross-sectional study in the northern region involving 1,567 patients found the prevalence of hernia to be 11.7%, with 85% of cases occurring in individuals aged 18 to 85 years.⁵ Additionally, a 2017 nationwide study found that 38% of 500 participants had abdominal hernias, with prevalence increasing with BMI and decreasing in younger populations.⁶

Hernia repair, whether performed through open or laparoscopic procedures, remains the primary treatment for all types of hernias. In recent years, mesh hernia repair has largely replaced non-mesh repair due to its superior postoperative outcomes.⁷ A systematic review of 25 studies involving 6,293 participants revealed that mesh hernia repair reduces the risk of recurrence compared to non-mesh repair. It also showed that mesh repair is associated with shorter surgery times, enhanced postoperative pain relief, and a lower risk of neurovascular or visceral injuries.⁸ Despite the advantages of mesh hernia repair, outcomes may still be influenced by the presence of diabetes mellitus.

Diabetes mellitus generally affects immunity and increases the risk of infections. A retrospective study conducted in Canada investigated infection rates and mortality due to bacterial infections in over 500,000 diabetic patients and age-matched controls across two separate periods. The findings revealed significantly higher infection rates among individuals with diabetes, with bacterial infections being the most prevalent.⁹ Diabetes mellitus represents a major global health concern, with an estimated 171 million diagnosed cases in 2000.¹⁰ This number has steadily risen, reaching 366 million in 2011, and is projected to surpass 522 million by 2030. This global epidemic also affects the Kingdom of Saudi Arabia (KSA). The Saudi Ministry of Health reported that in 1992, approximately 0.9 million individuals had diabetes, a figure that increased to 2.5 million by 2010, marking a 2.7-fold rise in incidence.¹⁰

The World Health Organization (WHO) has reported that Saudi Arabia ranks second in the Middle East and seventh globally in terms of diabetes prevalence. Approximately 7 million people in the country are affected by diabetes, with an additional 3 million individuals having pre-diabetes.¹¹ Diabetes mellitus is associated with a higher risk of complications, including delayed wound healing, increased susceptibility to infections, nutrient loss due to glycosuria, delayed extubation, and respiratory and circulatory abnormalities.^12,13 While several studies have highlighted differences in wound healing and postoperative outcomes between diabetic and non-diabetic patients, fewer have explored whether complications are more prominent in all diabetic patients or specifically in those with uncontrolled HbA1C levels.⁴ Determining whether a significant difference exists between diabetic patients with uncontrolled HbA1C levels (>7%) and those with controlled levels (<7%) is valuable. Such findings could assist in managing surgical outcomes, guiding surgeons' decisions regarding elective surgeries.

Numerous studies have explored the impact of diabetes mellitus on postoperative outcomes, yet the results remain inconclusive. Some research indicates that patients with high HbA1c levels, a history of diabetes, or preoperative hyperglycemia are more likely to experience increased postoperative infection rates. In fact, many surgeons suggest that individuals with diabetes often do not heal as well post-surgery as those without diabetes.^14–16 In our study, however, we found no significant association between HbA1C levels—whether controlled or uncontrolled—and postoperative outcomes. While the rate of wound infections was higher in patients with uncontrolled HbA1C, this difference was not statistically significant. Interestingly, a systematic review examining the relationship between HbA1C and sternal wound infections following adult cardiac surgery reported a substantially higher risk of infection when HbA1C levels exceeded 6-7%.¹⁷ The lack of a significant finding in our study may be attributed to the small sample size or the fact that wound infection rates are influenced by multiple risk factors, not just HbA1C levels. These factors may include the type of surgical wound (e.g., clean vs. clean-contaminated), patient age, and surgical risk classification.⁴ Our findings suggest that solely screening diabetic patients undergoing elective hernia surgery based on HbA1C levels is insufficient. A more comprehensive assessment, taking into account all relevant risk factors for wound infection and other postoperative complications, is essential.

Although previous studies have indicated a significant association between hernia recurrence and diabetes in patients undergoing open umbilical hernia repair,¹⁸ our study did not find a statistically significant difference in recurrence rates between patients with controlled and uncontrolled preoperative HbA1C levels, both postoperatively and during follow-up. This suggests that the risk of hernia recurrence may be inherent, regardless of whether the patient has controlled their HbA1C. Another possible explanation for the lack of significant differences between controlled and uncontrolled HbA1C groups could be the influence of other confounding factors, including the choice of surgical approach, BMI, age, gender, the presence of postoperative infection, smoking status, and other variables. The exact relationship between diabetes mellitus and hernia recurrence remains unclear, highlighting the need for further studies to explore this association more comprehensively.

In this study, no significant association was found between open hernia repair and a higher likelihood of wound infection compared to laparoscopic hernia repair. This aligns with the findings of a second study, which reported that laparoscopic ventral hernia repair (LVHR) was significantly associated with fewer surgical site infections (SSIs) but more clinical cases of bulging compared to open ventral hernia repair (OVHR).¹⁹ Similarly, a cohort study observed higher postoperative complications and hernia recurrence in laparoscopic procedures than in open ones, though these differences were not statistically significant.¹⁸ The discrepancies between these findings could be attributed to factors such as demographic characteristics, patients’ awareness of postoperative care, or the sample size. Larger, more inclusive studies are needed to clarify the outcomes of these different surgical approaches.

We recognize several limitations in our study. The inclusion criteria were broad, encompassing all diabetic patients who underwent hernia surgery, without specifying the type of hernia, as this would have further reduced the sample size. While we acknowledge that the sample size is relatively small, we believe that our study is the first to focus on a sufficiently small group of diabetic patients, allowing for an in-depth analysis to assess whether HbA1c levels, as an independent factor, influence postoperative infection rates specifically in hernia surgery cases.

Conclusion

Our study contributes to the existing knowledge in clean wound surgery (e.g., hernia) by demonstrating that the rates of wound infection and recurrence among patients with uncontrolled HbA1c were not statistically significant. However, a significant relationship was observed between hypertension and HbA1c levels. Future research should investigate the interaction between comorbid conditions (e.g., hypertension), HbA1c levels, and the incidence of postoperative wound infections.

Reporting guidelines

Figshare: STROBE Checklist for The association between HBA1C level and the outcome of hernia surgery in diabetic patients managed at a tertiary center: A retrospective cohort study, 10.6084/m9.figshare.28560725.²⁰

Ethics

Ethical approval was obtained in 30 May 2023 from the Institutional Review Board (IRB) of the King Abdullah International Medical Research Center (KAIMRC) with the approval number of (IRB/1297/23). Patient confidentiality and anonymity was strictly upheld, with no identifying information collected. All data, in both digital and physical formats, was secured and recorded in a password-protected Excel sheet, accessible exclusively to the research team. Furthermore, all data was securely maintained within the premises of the Ministry of National Guard Health Affairs (MNGHA).