High blood cholesterol is the presence of high levels of cholesterol in the blood. It is not a disease but a metabolic derangement that can be secondary to many diseases and can contribute to many forms of disease, most notably cardiovascular disease. It is closely related to the terms "hyperlipidemia" (elevated levels of lipids) and "hyperlipoproteinemia" (elevated levels of lipoproteins). Familial hypercholesterolemia is a rare genetic disorder that can occur in families, where sufferers cannot properly metabolise cholesterol.
Signs and symptoms
Elevated cholesterol does not lead to specific symptoms unless it has been longstanding. Some types of hypercholesterolemia lead to specific physical findings: xanthoma (thickening of tendons due to accumulation of cholesterol), xanthelasma palpabrum (yellowish patches around the eyelids) and arcus senilis (white discoloration of the peripheral cornea).
Longstanding elevated hypercholesterolemia leads to accelerated atherosclerosis; this can express itself in a number of cardiovascular diseases:
When measuring cholesterol, it is important to measure its subfractions before drawing a conclusion on the cause of the problem. The subfractions are LDL, HDL and VLDL. In the past, LDL and VLDL levels were rarely measured directly due to cost concerns. VLDL levels are reflected in the levels of triglycerides (generally about 45% of triglycerides is composed of VLDL). LDL was usually estimated as a calculated value from the other fractions (total cholesterol minus HDL and VLDL); this method is called the Friedewald calculation; specifically: LDL ~= Total Cholesterol - HDL - (0.2 x Triglycerides).
Less expensive (and less accurate) laboratory methods and the Friedewald calculation have long been utilized because of the complexity, labor and expense of the electrophoretic methods developed in the 1970s to identify the different lipoprotein particles which transport cholesterol in the blood. As of 1980, the original methods, developed by research work in the mid-1970s cost about $5K, US 1980 dollars, per blood sample/person.
With time, more advanced laboratory analyses have been developed which do measure LDL and VLDL particle sizes and levels, and at far lower cost. These have partly been developed and become more popular as a result of the increasing clinical trial evidence that intentionally changing cholesterol transport patterns, including to certain abnormal values compared to most adults, often has a dramatic effect on reducing, even partially reversing, the atherosclerotic process. With ongoing research and advances in laboratory methods, the prices for more sophisticated analyses have markedly decreased, to less than $100, US 2004, by some labs, and with simultaneous increases in the accuracy of measurement for some of the methods.
Screening for a disease refers to testing for a disease, such as hypercholesterolemia, in a patients who have no signs or symptoms of the disease.
In patients without any other risk factors, moderate hypercholesterolemia is often not treated. According to Framingham Heart Study, people with an age greater than 50 years have no increased overall mortality with either high or low serum cholesterol levels. There is, however, a correlation between falling cholesterol levels over the first 14 years and mortality over the following 18 years (11% overall and 14% CVD death rate increase per 1 mg/dL per year drop in cholesterol levels). This, however, does not mean that a decrease in serum levels is dangerous, as there has not yet been a recorded heart attack in the study in a person with a total cholesterol below 150 mg/dL.
The U.S. Preventive Services Task Force (USPSTF) has evaluated screening for hypercholesterolemia
Classically, hypercholesterolemia was categorized by lipoprotein electrophoresis and the Fredrickson classification. Newer methods, such as "lipoprotein subclass analysis" have offered significant improvements in understanding the connection with atherosclerosis progression and clinical consequences.
If the hypercholesterolemia is hereditary (familial hypercholesterolemia), there is more often a family history of premature, earlier onset atherosclerosis, as well as familial occurrence of the signs mentioned above.
There are a number of secondary causes for high cholesterol:
All three of these activities done together can have a positive effect on one's blood cholesterol level.