The survey research showed that the dyslipidemia prevalence among T2DM patients was 87.7%, the treatment rate was 68.0%, the overall control rates for LDL-C and non-HDL-C were 43.1% and 19.8% in Northwest China.
Dyslipidemia occurs very frequently in T2DM, influencing approximately 70.0% to 85.0% of patients [7, 8]. In this study, the dyslipidemia rate was 87.7%. The dyslipidemia rate in India was 85.5%-97.8% [11], and in Spain it was 81.2% [12], which is similar to this finding. While a study in North and East China showed dyslipidemia rate of 67.1% [6], which is lower than the dyslipidemia rate in this survey. Due to the high carbohydrate, high fat, low vegetable and low fruit diet; lack of exercise; and relatively poor economic level and medical conditions, the dyslipidemia rate is higher in Northwest China. In addition, the patient’s emphasis on self-health also affects the dyslipidemia rate. Moreover, high TG and low HDL-C contributed to the predominant dyslipidemia patterns in the subjects. Recent studies demonstrated that the common patterns of dyslipidemia included abnormal TG and HDL-C levels in patients with T2DM [13, 14]. In T2DM, insulin resistance and hyperglycemia induce elevated triglycerides, which leads to overproduction of glycerol-rich lipoproteins by the liver. The increase of triglyceride-rich lipoproteins generally correlates to a reduction in high-density lipoproteins and an addition in low-density lipoproteins [14, 15]. In turn, high TG and low HDL-C can lead to insulin resistance, resulting in poor glycemic control, which then creates a vicious cycle.
After lifestyle interventions, early medical treatment is the major approach to regulate dyslipidemia, and statins are recommended as the preferred lipid-lowering drugs according to the guidelines [3, 16]. This survey showed that 68.0% of T2DM patients with dyslipidemia were treated with lipid-lowering drugs, with a significant improvement in HDL-C level. A study in Korea showed that the treatment rate for DM was 26.9% [17], which decreased significantly compared with the results of this study. A 2015 survey in China revealed a 55.9% treatment rate among T2DM patients with dyslipidemia [6]. In the current study, the treatment rate for dyslipidemia reached 68.0%, indicating that China's attention to dyslipidemia has improved. For the lipid-lowering therapy, atorvastatin and rosuvastatin were the main drugs in this study, and the reasons are mainly related to the drug safety and efficacy [18, 19]. Although the harm of dyslipidemia is very serious, 32.0% of the patients were still untreated. Regression analysis found that non-treatment is associated with factors such as age ≤ 60 years, duration of T2DM ≤ 3 years, BMI ≥ 24, hypertension and FLD. The patients were in relatively good physical condition leading to neglect of the severity of the disease, as also demonstrated by the analysis of lipid control.
Lowering LDL-C levels is considered the primary goal for lipid management due to the significant reduction in CVD and mortality risk in DM patients, and lowering non-HDL-C levels is a secondary goal [3, 16]. This study indicated that the LDL-C control rate reached 43.1% overall, it was 51.7% for the high-risk and 36.1% for the very high-risk. However, only 19.8% of patients attained the non-HDL-C goal. An analysis in Europe and Canada showed that the TC and LDL-C control rates were 48.1% and 54.7% in the statin-using DM patients [20]. According to a survey in China by Li Yan in 2011, after treatment with lipid-lowering drugs, about 39.4% of the T2DM patients reduced the LDL-C level to below 2.6 mmol/L, and in very high-risk patients the control rate was 15.3% [6]. Compared with studies in developed countries such as Europe and Canada, the control rate of LDL-C in this present study is lower. However, compared to the results from Li Yan et al., the LDL-C control rate of this population is improved. Microvascular and macrovascular disease are common complications of T2DM. In people with complications, lipid control should be stricter in order to prevent further deterioration of the disease. However, the rate of non-HDL-C not at goal ranged from 76.0% to 83.0%, and it reached 83.0% for DKD patients. The rate of LDL-C non-attainment ranged from 54.8% to 63.9%, with the highest rate in patients with ASCVD. This result is particularly noteworthy for physicians.
The failure to achieve lipid control despite medical intervention is associated with various factors. The regression analysis found that the factors included HbA1c, age and hypertension in this study. Of these, HbA1c was the most relevant factor. Dyslipidemia has been suggested to have a linear relationship with HbA1c in recent studies, and HbA1c could reflect cholesterol and LDL levels among T2DM patients. A marked increase for TC and TG levels and a decrease for HDL-C levels compared to patients with good glycemic control [21,22,23]. For most patients with DM, the better the glycemic control, the more likely they are to exhibit a more active and healthy lifestyle that leads to better management of lipid levels [17]. The “healthy adherer-effect” [24, 25] seems to explain why the patients in this study with poor HbA1c control had lower rates of lipid control. Advanced age and high blood pressure have always been considered unfavorable factors for lipid control. However, this research found age > 60 years old and hypertension are beneficial to the treatment and lipid control. This may be related to the fact that patients who are older and in poorer physical condition are more aware of their disease and show a better treatment adherence, which leads to better lipid control. This phenomenon may be explained with “health belief model”, a theory which suggests that people believing they are sicker will adopt a healthier approach to decelerate disease progression [17].
One thousand two hundred thirty-one Chinese T2DM patient medical data were analyzed in this study. It is worth noting that the dyslipidemia prevalence in T2DM patients was 87.7%, the treatment rate was 68.0%, and the overall LDL-C and non-HDL-C control rates were 43.1% and 19.8%, respectively. Dyslipidemia should be given more attention from the public health perspective. First, early monitoring dyslipidemia is the basis for effective prevention of ASCVD. Second, lifestyle intervention is a fundamental measure for the treatment of dyslipidemia. In addition, individualised medication protocols have become the current trend in lipid intervention.
Study strength and limitation
This cross-sectional study provides the latest data on the prevalence, treatment rate and control rate of dyslipidemia among T2DM patients. This result may provide an effective therapeutic strategy for reducing CVD in patients with T2DM. Some limitations remain in this study. The cross-sectional design only can evaluate the relationship between dyslipidemia and the risk factors, and can not assess their exact causal effect. Moreover, this single-centre retrospective study had a small sample selection and number, resulting in the sample choice bias. In addition, there are no clear diagnostic criteria for dyslipidemia in patients with DM, the dyslipidemia prevalence may be lower.