Risk Factors:

Unhealthy cholesterol levels (low HDL, high LDL, and high triglycerides) increase the risk for heart disease and heart attack. Some risk factors for cholesterol can be controlled (diet, exercise, weight) while others cannot (age, gender, and family history).

Age and Gender

From puberty on, men tend to have lower HDL (“good” cholesterol) levels than women. One reason is that the female sex hormone estrogen is associated with higher HDL levels. Because of this, premenopausal women generally have lower rates of heart disease than men. After menopause, as estrogen levels decline, women catch up in their rates of heart disease. Throughout the menopausal years, HDL levels decrease and LDL (“bad” cholesterol) and triglyceride levels increase. For men, LDL and triglyceride levels also rise as they age and the risks for heart disease increase as well. (There is some evidence that high triglyceride levels carry more risks for women than men.) Heart disease is the main cause of death for both men and women.

Children and Adolescents. Children who have abnormal cholesterol levels are at increased risk of developing heart disease later in life. However, it is difficult to distinguish “normal” cholesterol levels in children. Changes in cholesterol levels occur between the ages of 8 - 18, and vary between genders and population groups. Cholesterol levels tend to naturally rise sharply until puberty, decrease sharply, and then rise again.

Genetic Factors and Family History

Genetics play a major role in determining a person's blood cholesterol levels. (Children from families with a history of premature heart disease should be tested for cholesterol levels after they are 2 years old.) Genes may influence whether a person has low HDL levels, high LDL levels, high triglycerides, or high levels of other lipoproteins, such as lipoprotein(a).

Inherited cholesterol disorders include:

• Familial hypercholesterolemia is a genetic disorder that causes high cholesterol levels, particularly LDL, and premature heart disease. It occurs in as many as 1 in 500 people.
• Familial lipoprotein lipase deficiency is a very rare disorder that causes depletion of lipoprotein lipase. This is an enzyme that appears to be important in the removal of lipoproteins that are rich in triglycerides. People who are deficient in it have high levels of cholesterol and fat in their blood.

Lifestyle Factors

Diet. The primary dietary elements that lead to unhealthy cholesterol include saturated fats (found mainly in red meat, egg yolks, and high-fat dairy products) and trans fatty acids (found in fried foods and some commercial baked food products). Shellfish is also high in dietary cholesterol.

Weight. Being overweight or obese increases the risks for unhealthy cholesterol levels.

Exercise. Lack of exercise can contribute to weight gain, decreases in HDL levels, and increases in LDL and total cholesterol levels.

Smoking. Smoking reduces HDL cholesterol and promotes build-up of fatty deposits in the coronary arteries.

Obesity, Metabolic Syndrome, and Type 2 Diabetes

In the U.S., obesity is at epidemic levels in all age groups. The effect of obesity on cholesterol levels is complex. Overweight individuals tend to have high triglyceride and LDL levels and low HDL levels. This combination is a risk factor for heart disease. Obesity also causes other effects (high blood pressure, increase in inflammation) that pose major risks to the heart.

Obesity is particularly dangerous when it is one of the components of the metabolic syndrome, formerly known as syndrome X. This syndrome consists of obesity marked by abdominal fat, unhealthy cholesterol levels, high blood pressure, and insulin resistance. Metabolic syndrome is a pre-diabetic condition that is significantly associated with heart disease and higher mortality rates from all causes. Many doctors recommend that patients with metabolic syndrome should be aggressively treated with high-dose statin therapy to lower LDL levels.

Obesity is also strongly associated with type 2 diabetes, which itself poses a significant risk for high cholesterol levels and heart disease.

Children who are overweight are at higher risk for high triglycerides and low HDL, which may be directly related to later unhealthy cholesterol levels. Childhood LDL levels and body-mass index (BMI) are strongly associated with cardiovascular risk during adulthood. Overweight and obese children who have high cholesterol should also get tested for high blood pressure, diabetes, and other conditions associated with metabolic syndrome.

[For more information, see In-Depth Report #60: Diabetes type 2.]

Other Medical Conditions

High Blood Pressure. High blood pressure (hypertension) contributes to the thickening of the heart� ' s blood vessel walls, which can worsen atherosclerosis (accumulated deposits of cholesterol in the blood vessels.) High blood pressure, high cholesterol, and diabetes all work together to increase the risk for developing heart disease. [For more information, see In-Depth Report #14: High blood pressure.]

Hypothyroidism. Low thyroid levels (hypothyroidism) are associated with higher risk for high total and LDL cholesterol, and triglycerides. Treating the thyroid condition can significantly reduce cholesterol levels. Research is mixed on whether mild hypothyroidism (subclinical hypothyroidism) is associated with unhealthy cholesterol levels. [For more information, see In-Depth Report #38: Hypothyroidism.]

Hypothyroidism is a decreased activity of the thyroid gland which may affect all body functions. In this condition, the rate of metabolism slows, causing mental and physical sluggishness. The most severe form of hypothyroidism is myxedema, which is a medical emergency.

Polycystic Ovarian Syndrome. Women with this endocrine disorder may hav increased risks for high triglyceride and low HDL levels. This risk may be due to the higher levels of the male hormone testosterone associated with this disease.

Kidney Disease. Kidney disease increases the risk of heart disease.

Other Risk Factors

Medications. Certain medications such as specific antiseizure drugs, corticosteroids, and isotretinoin (Accutane) may increase lipid levels.