Body Surface Area: A New Anthropometric Measurement for Diabetic Retinopathy in Chinese Adults with Type 2 Diabetes: A Hospital Registry Case-Control Study
Diabetic retinopathy (DR) is a severe complication of diabetes mellitus, characterized by retinal microvascular damage. As the leading cause of blindness in adults, DR has emerged as a significant public health concern worldwide, threatening the outcomes of diabetic patients and even the general population. The relationship between DR and common anthropometric measurements, such as body mass index (BMI), has been controversial. Body surface area (BSA), another anthropometric index calculated using height and weight, is considered to more accurately reflect body size and distinguish between adipose and muscle tissues. Additionally, previous research has suggested that adipokines secreted from adipose tissue may play a crucial role in the mechanisms of obesity and type 2 diabetes. Specifically, lower levels of adiponectin in obese individuals may contribute to insulin resistance and diabetes. This study is the first to investigate the relationship between BSA and DR in Chinese adults with type 2 diabetes, comparing it with BMI.
The study was approved by the Institutional Review Board of the First Affiliated Hospital of China Medical University, and written informed consent was obtained from all participants. This hospital registry case-control study involved 2,454 Chinese subjects aged 18 years or older who were inpatients with type 2 diabetes. The selection of cases and controls followed a specific procedure outlined in Supplementary Figure 1. Type 2 diabetes was defined according to the American Diabetes Association standards, and DR was evaluated using the Early Treatment Diabetic Retinopathy Study and International Classification Diabetic Retinopathy Scales. DR severity was categorized into four levels: non-DR, mild non-proliferative DR (NPDR), moderate NPDR, and vision-threatening DR (VTDR). BMI was calculated as weight in kilograms divided by height in meters squared, while BSA was calculated using a specific formula.
The basic characteristics of the participants were summarized in Table 1, which included detailed assessments conducted at the time of their initial admission. One-way analysis of variance and Chi-squared tests were used to explore the correlations between variables and DR severity. Among all variables, the duration of diabetes, heart rate, systolic blood pressure, pulse pressure, weight, BMI, and BSA levels were significantly associated with DR severity. The correlation between any-severity DR and BSA was significant, with a P-value of 0.025, whereas the correlation between any-severity DR and BMI was not significant. When analyzing by gender, BSA levels decreased significantly with advanced DR severity in males but not in females, likely due to differences in body fat distribution between genders.
Receiver operating characteristic curves were used to estimate the predictive value of BMI and BSA, with the results depending on the area under the curve (AUC). BSA levels were significant in predicting VTDR in the overall population and in males, while BMI also showed significance in predicting VTDR. However, only BSA had notable predictive effects for any-severity DR. These findings suggest that BSA is more closely related to DR and its severity, particularly in males.
BSA was divided into quartiles, and variables were compared according to these quartiles. The trend of BSA quartiles and DR severity in different genders was shown in Supplementary Figure 2. Three multivariable-adjusted models were designed to investigate the associations between DR severity and BSA levels using logistic regression, with non-DR as the reference. After adjusting for age and gender, BSA was significantly associated with any-severity DR and VTDR. Further adjustments in the models did not change these significant associations. When including only male participants, the results of logistic regression were more meaningful, showing significant associations in any-severity DR and VTDR groups, as well as in the mild NPDR group.
BSA quartiles were also regarded as categorized variables, with Q1 as the reference. Logistic regressions showed a remarkable dose-response trend between BSA quartiles and any-severity DR, as well as VTDR, indicating a negative correlation between BSA quartiles and the risk of DR and VTDR. Similar dose-response relationships were statistically significant in mild NPDR for males, with odds ratios decreasing as BSA quartiles increased.
To date, few studies have explored the relationship between BSA level and diabetic microangiopathy. This study demonstrated that BSA is inversely correlated with DR severity more strongly than BMI, proving to be an independent predictor of DR in Chinese adults with type 2 diabetes. However, this association should be interpreted cautiously in females. While these findings are significant, it is not yet conclusive whether actively improving BMI or BSA levels can prevent DR. More prospective studies, including those beyond hospitalized patients, are needed to support the potential benefits of higher BSA levels for DR prevention.
doi.org/10.1097/CM9.0000000000001071
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