A recent study published in the journal Scientific Reports assessed the associations between the change in total cholesterol (TC) levels after type 2 diabetes (T2D) diagnosis (relative to pre-diagnosis levels) and risk of cardiovascular disease (CVD).
CVD is the leading cause of death worldwide. T2D is a gateway to CVD. One study revealed higher coronary heart disease (CHD) and stroke risks in diabetic patients than in non-diabetics. The global prevalence of T2D is expected to exceed 10% by 2030. Therefore, preventing CVD in people with diabetes may be of public health importance.
Hypercholesterolemia is a significant risk factor for CVD and the adverse effects on CVD may be more pronounced in individuals with metabolic disorders, e.g. T2D. Diabetic patients may be more susceptible to the negative influence of hypercholesterolemia on the risk of cardiovascular disease. Nevertheless, the T2D diagnosis often results in positive lifestyle changes, reducing the risk of hypercholesterolemia or cardiovascular disease.
Study: Changes in Total Cholesterol Levels and Risk of Cardiovascular Disease in Patients with Type 2 Diabetes. Image Credit: Crystallight / Shutterstock
About the study
In the current study, researchers examined the relationship between the change in TC levels pre- and post-T2D diagnosis with the risk of CVD. They selected participants with T2D from 2003 to 2012 from the National Health Insurance Service – Health Screening cohort in Korea. Patients were identified using relevant International Classification of Diseases, Tenth Revision (ICD-10) codes and by antidiabetic drug history.
Circulating TC levels were estimated after an eight-hour fast. TC levels two years before and after T2D diagnosis were classified into low (< 180 mg/dL), intermediate (180 to 239 mg/dL), and high (≥ 240 mg/dL). Accordingly, participants were stratified into high-low, high-mid, high-high, mid-low, mid-mid, mid-high, low-low, low-mid, and low-high groups based on the change in TC levels after T2D diagnosis from pre-diagnosis levels.The primary endpoint was the incidence of non-fatal CVD. The secondary outcome measure was the incidence of stroke or CHD. The team calculated the cumulative probability of CVD incidence based on changes in TC levels. Hazard ratios of outcomes were calculated using the Cox proportional hazard model. In addition, the team performed a subgroup analysis based on the use of lipid-lowering drugs. Sensitivity analyzes were limited to those taking statins.
The study included 23,821 participants; 9.9% were diagnosed with CVD. The incidence of CHD and stroke was 4.9% and 5.1%, respectively. Patients with elevated TC levels after T2D diagnosis were likely to have greater use of lipid-lowering drugs, body mass index (BMI), fasting serum glucose, blood pressure, aspartate transaminase, alanine transaminase, and lower physical activity compared to those who had constant or unchanged TC levels after T2D diagnosis.
Most of the participants taking lipid-lowering drugs were on statins. The cumulative probability of the incidence of non-fatal CVD in T2D patients was significantly increased in the low-mid, low-high, and mid-high groups. Conversely, it was significantly lower in mid-low, high-mid, and high-low groups. Higher and lower TC levels after T2D diagnosis were associated with increased and decreased CVD risk, respectively.
CVD risk increased in the low-middle and low-high groups, but decreased in the high-middle group among participants not taking lipid-lowering drugs. Among patients taking these drugs, the risk of CVD was higher in the low-mid group, but lower in the high-middle and high-low groups. There was no evidence of interactions between the use of lipid-lowering drugs and the change in TC levels in the subgroup analysis.
The association of the change in TC levels was consistent for CHD or stroke risk, but differed with the use of lipid-lowering drugs in the subgroup analysis. However, the results were not different in sensitivity analyzes limited to statin users. In addition, the researchers performed analyzes on participants with data on high-density (HDL-C) or low-density lipoprotein cholesterol (LDL-C) and triglycerides.
There was no association between cardiovascular disease risk and changes in triglyceride and HDL-C levels before and after T2D diagnosis. However, a 10 mg/dL increase in LDL-C levels after T2D diagnosis relative to pre-diagnosis levels was associated with a higher risk of CVD and CHD, particularly in those taking lipid-lowering drugs.
Overall, increased TC levels in T2D patients relative to pre-diagnosis levels were associated with a higher CVD risk, while decreased TC levels were associated with a lower CVD risk, regardless of the use of lipid-lowering drugs. The results were consistent for stroke and CHD risk. Women probably did not show improvements in TC levels despite taking lipid-lowering drugs. Therefore, the findings suggest that controlling TC levels in T2D patients may be clinically significant in reducing CVD risk.