[Association between obesity and the risk of microvascular complications in Yinzhou District, Ningbo adults with type 2 diabetes mellitus].

Objective: To investigate the association between various obesity indices and the risk of developing microvascular complications in adult patients with Type 2 diabetes(T2DM), using cohort data derived from Yinzhou District Health Big Data Platform of China.

Methods: This study included adult patients with type 2 diabetes(T2DM) who were enrolled between January 1, 2008, and December 31, 2013, in Yinzhou District, Ningbo, and did not have any microvascular complications at baseline. Data collection encompassed demographic characteristics, lifestyle behaviors, laboratory test result, and physical examination findings, obtained at both baseline and during follow-up periods through structured epidemiological surveys and clinical assessments. Various obesity indices were calculated, including body mass index(BMI), waist-to-height ratio(WHtR), a body shape index(ABSI) and body roundness index(BRI). We also computed the coefficients of variation for these obesity indices during the follow-up period. A Cox proportional hazards regression model was used to analyze the association between obesity indices at baseline and follow-up, and the risk of developing microvascular complications. Additionally, receiver operating characteristic(ROC) curves were used to analyze the predictive efficacy of the coefficients of variation for BMI, WHtR, ABSI and BRI in relation to microvascular complications, and the areas under the curve(AUCs) were calculated.

Results: A total of 27 635 patients with type 2 diabetes(T2DM) were included, contributing to 153 717 person-years of follow-up. During this period, 12 969 new cases of microvascular complications were identified, resultsing in an incidence rate of 84.37 cases per 1000 person-years. Patients were categorized into two groups based on the occurrence of complications: those with microvascular complications and those without. There was no significant difference in blood glucose levels between the two groups at baseline. After adjusting for sociodemographic characteristics, laboratory indicators, and potential confounders such as a history of hypertension and hyperlipidemia, it was found that only the WHtR(HR=1.027, 95%CI 1.008-1.046), ABSI(HR=1.035, 95%CI 1.018-1.053) and BRI(HR=1.030, 95%CI 1.011-1.049) were independently associated with the risk of microvascular complications at baseline, while waist circumference(HR=1.010, 95%CI 0.992-1.029) and BMI(HR=0.985, 95%CI 0.967-1.002) were not significantly related(P>0.05). During the follow-up period, the coefficients of variation for all obesity indices were independently associated with an increased risk of microvascular complications. Among them, abdominal obesity indices, such as waist circumference(HR=0.063, 95%CI 1.057-1.069), WHtR(HR=1.060, 95%CI 1.054-1.066), and ABSI(HR=1.062, 95%CI 1.058-1.066), were most strongly linked to the risk of microvascular complications. Further stratified analysis based on baseline BMI revealed that the variability in abdominal obesity indices was more strongly associated with microvascular complications in patients with normal and overweight BMI compared to those with obesity. Specifically, the following result were observed: waist circumference(HR_(normal BMI)=1.074, HR_(overweight)=1.059, HR_(obesity)=1.041; P<0.01), WHtR(HR_(normal BMI)=1.069, HR_(overweight)=1.059, HR_(obesity)=1.037; P<0.01), ABSI(HR_(normal BMI)=1.065, HR_(overweight)=1.067, HR_(obesity)=1.038; P<0.01), BRI(HR_(normal BMI)=1.023, HR_(overweight)=1.020, HR_(obesity)=1.011; P<0.01). Additionally, to further explore the predictive value of various obesity indices for microvascular complications in type 2 diabetes mellitus(T2DM), we conducted stratified analyses based on sex and age(using 60 years as the cutoff). WHtR showed similar predictive performance between men(AUC = 0.794) and women(AUC=0.789). However, WHtR demonstrated stronger predictive ability in individuals over 60 years old(AUC = 0.803) compared to those aged 60 years or younger(AUC = 0.777). ABSI exhibited a higher predictive value in men(AUC = 0.752) than in women(AUC = 0.730), and again, the index performed better in the older population(AUC = 0.761) than in the younger group(AUC = 0.725). Similarly, BRI demonstrated comparable performance between sexes [men(AUC = 0.796) and women(AUC = 0.791)] with the highest predictive accuracy seen in participants over 60 years(AUC = 0.806). By contrast, BMI showed relatively lower predictive power across all subgroups. Specifically, the AUC values for BMI were 0.744 in men and 0.714 in women, 0.714 in those aged 60 years or below and 0.748 in those above 60 years.

Conclusion: Increased baseline abdominal obesity indices(WHtR, ABSI and BRI) and higher variability in obesity indices during follow-up are strongly associated with increased risks of microvascular complications in T2DM patients. In individuals with normal BMI, higher variability in abdominal obesity indices is positively correlated with the risk of microvascular complications. Furthermore, the variability in abdominal obesity indices(WHtR, ABSI and BRI) provides better predictive ability for microvascular complications compared to general obesity indices(BMI), especially in male patients and those aged over 60.