Final answer:
An increase in serum LDL levels is positively correlated with an increased risk of coronary heart diseases, since LDL (bad cholesterol) leads to plaque buildup in arteries, causing atherosclerosis.
Step-by-step explanation:
An increase in serum levels of low-density lipoprotein (LDL) is indeed positively correlated with a risk of coronary heart diseases. LDL is commonly referred to as 'bad' cholesterol because it can lead to the buildup of plaque in the arteries. This buildup, known as atherosclerosis, narrows the arteries and can result in coronary artery disease. On the other hand, high-density lipoprotein (HDL) is considered the 'good' cholesterol transporter as it helps remove cholesterol from the arteries.
Unhealthy lifestyle choices such as eating foods high in saturated and trans fats, lack of physical activity, and smoking are common causes of elevated LDL levels. Maintaining a low LDL level (less than 100 mg/dL) while keeping a high HDL level is important for reducing cardiovascular disease risks. The LDL:HDL ratio is a critical marker for heart disease risk, and a higher ratio indicates a heightened risk.