Hypercholesterolemia

DiseaseDisorder infobox
Name = Hypercholesterolemia


Caption = Cholesterol
ICD10 = ICD10|E|78|0|e|70
ICD9 = ICD9|272.0
ICDO =
OMIM =
DiseasesDB = 6226
MedlinePlus =
eMedicineSubj = med
eMedicineTopic = 1073
MeshID = D006937

Hypercholesterolemia (literally: high blood cholesterol) is the presence of high levels of cholesterol in the blood cite journal |author=Durrington P |title=Dyslipidaemia |journal=Lancet |volume=362 |issue=9385 |pages=717–31 |year=2003 |pmid=12957096 |doi=10.1016/S0140-6736(03)14234-1] . 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).

Elevated cholesterol in the blood is due to abnormalities in the levels of lipoproteins, the particles that carry cholesterol in the bloodstream. This may be related to diet, genetic factors (such as LDL receptor mutations in familial hypercholesterolemia) and the presence of other diseases such as diabetes and an underactive thyroid. The type of hypercholesterolemia depends on which type of particle (such as low density lipoprotein) is present in excess.

High cholesterol levels are treated with diets low in cholesterol, medications, and rarely with other treatments including surgery (for particular severe subtypes). This is also increased emphasis on other risk factors for cardiovascular disease, such as high blood pressure.

igns 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 (deposition of cholesterol in patches on the skin or in tendons), "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: coronary artery disease (angina pectoris, heart attacks), stroke and short stroke-like episodes and peripheral vascular disease. [cite journal |author=Grundy SM, Balady GJ, Criqui MH, "et al" |title=Primary prevention of coronary heart disease: guidance from Framingham: a statement for healthcare professionals from the AHA Task Force on Risk Reduction. American Heart Association |journal=Circulation |volume=97 |issue=18 |pages=1876–87 |year=1998 |pmid=9603549 |url=http://circ.ahajournals.org/cgi/content/full/97/18/1876]

Diagnosis

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. In 1980, the original methods, developed by research work in the mid-1970s cost about $5,000, in 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.

Classification

Fredrickson classification

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.

econdary causes

There are a number of secondary causes for high cholesterol:
* Diabetes mellitus and metabolic syndrome
* Kidney disease (nephrotic syndrome)
* Hypothyroidism
* Anorexia nervosa
* Zieve's syndrome
* Family history
* Diet: Saturated fat raises blood cholesterol levels. Although dietary cholesterol exerts some influence, the regulatory mechanism of the liver upon absorption of cholesterol decreases the effect of dietary cholesterol on total cholesterol levels. Thus it is mainly by limiting the amount of saturated fat in one's diet that helps lower total serum cholesterol.Fact|date=February 2007
*Body Weight. Being overweight is a definite risk factor for heart disease. It also tends to increase your cholesterol. Losing weight can help lower your LDL and total cholesterol levels, as well as raise your HDL and lower your triglyceride levels.
*Physical Activity. Lack of physical activity is a risk factor for heart disease. Regular physical activity can also help lower LDL (bad) cholesterol and raise HDL (good) cholesterol levels. It also helps you lose weight.

All three of these activities done together can have a positive effect on one's blood cholesterol level.

Dietary influence

While part of the circulating cholesterol originates from diet, and restricting cholesterol intake may reduce blood cholesterol levels, there are various other links between the dietary pattern and cholesterol levels. The American Heart Association also compiles a list of the acceptable/unacceptable foods for those who are diagnosed with hypercholesterolemia.

Dietary changes can potentially be very strong: when a group of Tarahumara Indians from Mexico with no obesity and cholesterol problems were exposed to a Western diet, their risk profile worsened significantly, with cholesterol levels rising over thirty percent.cite journal |author=McMurry MP, Cerqueira MT, Connor SL, Connor WE |title=Changes in lipid and lipoprotein levels and body weight in Tarahumara Indians after consumption of an affluent diet |journal=N. Engl. J. Med. |volume=325 |issue=24 |pages=1704–8 |year=1991 |pmid=1944471 |doi=|url=http://content.nejm.org/cgi/content/abstract/325/24/1704]

Carbohydrates

Evidence is accumulating that eating more carbohydrates - especially simpler, more refined carbohydrates - increases levels of triglycerides in the blood, lowers HDL, and may shift the LDL particle distribution pattern into unhealthy atherogenic patterns.

Trans fats

An increasing number of researchers are suggesting that a major dietary risk factor for cardiovascular diseases is trans fatty acids, and in the US the FDA has revised food labeling requirements to include listing trans fat quantities. [cite journal |author=Mozaffarian D, Katan MB, Ascherio A, Stampfer MJ, Willett WC |title=Trans fatty acids and cardiovascular disease |journal=N. Engl. J. Med. |volume=354 |issue=15 |pages=1601–13 |year=2006 |month=April |pmid=16611951 |doi=10.1056/NEJMra054035]

Treatment

Any decision to treat elevated risk

[http://clinicalevidence.com Clinical Evidence] has summarized treatment for both primary prevention cite journal |author=Pignone M |title=Primary prevention: dyslipidaemia |journal=Clin Evid |volume= |issue= |pages=142–50 |year= |pmid=16620402 | url=http://clinicalevidence.com/ceweb/conditions/cvd/0215/0215.jsp] and secondary prevention cite journal |author=Gami A |title=Secondary prevention of ischaemic cardiac events |journal=Clin Evid |volume= |issue= |pages=195–228 |year= |pmid=16973010 | url=http://clinicalevidence.com/ceweb/conditions/cvd/0206/0206_guidelines.jsp] . Two factors to consider when choosing therapy are the patient's risk of coronary disease and their lipoprotein pattern.

:Risk of coronary disease. To calculate the benefit of treatment, there are two online calculators that can estimate baseline risk cite web |url=http://www.med-decisions.com/ |title=med-decisions.com |accessdate= |accessmonthday=Feb 26 |accessdaymonth = |accessyear=2007 |author= Pignone MP |last= |first= |authorlink= |coauthors= Sheridan SL |date= |year= |month= |format= |work= |publisher= |pages= |language= |archiveurl= |archivedate= |quote= ] cite web |url=http://hp2010.nhlbihin.net/atpiii/calculator.asp?usertype=prof |title=10-year CVD Risk Calculator (Risk Assessment Tool for Estimating 10-year Risk of Developing Hard CHD (Myocardial Infarction and Coronary Death) Version) |accessdate= |accessmonthday=Feb 26 |accessdaymonth = |accessyear=2007 |author= National Cholesterol Education Program |last= |first= |authorlink= |coauthors= |date= |year= |month= |format= |work= |publisher= |pages= |language= |archiveurl= |archivedate= |quote= ] . Combining the baseline risk with the relative risk reduction of a treatment can lead to the absolute risk reduction of number needed to treat. For example, one of the calculators projects that a patient had a 10% risk of coronary disease over ten years. As noted below, the relative risk reduction of a statin is 30%. Thus, after 4-7 years of treatment with a statin, a patient's risk will drop to 7%. This equates to an absolute risk reduction of 3%, or a number needed to treat of 33. Thirty three such patients must be treated for 4-7 years for one to benefit.

:Lipoprotein patterns. ("See hyperlipoproteinemia for details") The treatment depends on the type of hypercholesterolemia. Clinical trials, starting in the 1970s, have repeatedly and increasingly found that "normal" cholesterol values do not necessarily reflect healthy cholesterol values. This has increasingly lead to the newer concept of dyslipidemia, despite normo-cholesterolemia. Thus there has been increasing recognition of the importance of "lipoprotein subclass analysis" as an important approach to better understand and change the connection between cholesterol transport and atherosclerosis progression. Fredrickson Types IIa and IIb can be treated with diet, statins (most prominently rosuvastatin, atorvastatin, simvastatin, or pravastatin), cholesterol absorption inhibitors (ezetimibe), fibrates (gemfibrozil, bezafibrate, fenofibrate or ciprofibrate), vitamin B3 (niacin), bile acid sequestrants (colestipol, cholestyramine), LDL apheresis and in hereditary severe cases liver transplantation.

Multiple clinical trials, each, by design, examining only one of multiple relevant issues, have increasingly examined the connection between these issues and atherosclerosis clinical consequences. Some of the better recent randomized human outcome trials include ASTEROID, ASCOT-LLA, REVERSAL, PROVE-IT, CARDS, Heart Protection Study, HOPE, PROGRESS, COPERNICUS, and especially a newer research approach utilizing a synthetically produced and IV administered human HDL, the Apo A-I Milano TrialFact|article|date=February 2007.

Diet

In strictly controlled surroundings, such as a hospital ward dedicated to metabolsim problems, a diet can reduce cholesterol levels by 15%. In practice, dietary advice can provide a modest decrease in cholesterol levels and may be sufficient in the treatment of mildly elevated cholesterol. [cite journal |author=Tang JL, Armitage JM, Lancaster T, Silagy CA, Fowler GH, Neil HA |title=Systematic review of dietary intervention trials to lower blood total cholesterol in free-living subjects |journal=BMJ |volume=316 |issue=7139 |pages=1213–20 |year=1998 |month=April |pmid=9552999 |pmc=28525 |doi= |url=http://www.bmj.com/cgi/content/abstract/316/7139/1213]

Medications

Many primary physicians and heart specialists will initially prescribe medication in combination with diet and exercise. According to various resources, statins are the most commonly used and effective forms of medication for the treatment of high cholesterol. The [http://www.ahrq.gov/clinic/uspstfix.htm U.S. Preventive Services Task Force (USPSTF)] estimated that after 5 to 7 years of treatment, the relative risk reduction by statins on coronary heart disease events is decreased by approximately 30% More recently, a meta-analysis reported an almost identical relative risk reduction of 29.2% in low risk patients treated for 4.3 years cite journal |author=Thavendiranathan P, Bagai A, Brookhart M, Choudhry N |title=Primary prevention of cardiovascular diseases with statin therapy: a meta-analysis of randomized controlled trials |journal=Arch Intern Med |volume=166 |issue=21 |pages=2307–13 |year=2006 |pmid=17130382 |doi=10.1001/archinte.166.21.2307] . A relative risk reduction of 19% in coronary mortality was found in a meta-analysis of patients at all levels of risk.cite journal |author=Baigent C, Keech A, Kearney PM, "et al" |title=Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins |journal=Lancet |volume=366 |issue=9493 |pages=1267–78 |year=2005 |pmid=16214597 |doi=10.1016/S0140-6736(05)67394-1]

Clinical practice guidelines

Various clinical practice guidelines have addressed the treatment of hypercholesterolemia. The American College of Physicians has addressed hypercholesterolemia in patients with diabetes cite journal |author=Snow V, Aronson M, Hornbake E, Mottur-Pilson C, Weiss K |title=Lipid control in the management of type 2 diabetes mellitus: a clinical practice guideline from the American College of Physicians |journal=Ann Intern Med |volume=140 |issue=8 |pages=644–9 |year=2004 |pmid=15096336 | url=http://www.annals.org/cgi/content/full/140/8/644] . Their recommendations are:
* Recommendation 1: Lipid-lowering therapy should be used for secondary prevention of cardiovascular mortality and morbidity for all patients (both men and women) with known coronary artery disease and type 2 diabetes.
* Recommendation 2: Statins should be used for primary prevention against macrovascular complications in patients (both men and women) with type 2 diabetes and other cardiovascular risk factors.
* Recommendation 3: Once lipid-lowering therapy is initiated, patients with type 2 diabetes mellitus should be taking at least moderate doses of a statin (the accompanying evidence report states "simvastatin, 40 mg/d; pravastatin, 40 mg/d; lovastatin, 40 mg/d; atorvastatin, 20 mg/d; or an equivalent dose of another statin")cite journal |author=Vijan S, Hayward RA |title=Pharmacologic lipid-lowering therapy in type 2 diabetes mellitus: background paper for the American College of Physicians |journal=Ann. Intern. Med. |volume=140 |issue=8 |pages=650–8 |year=2004 |pmid=15096337 |doi=|url=http://www.annals.org/cgi/content/full/140/8/650] .
* Recommendation 4: For those patients with type 2 diabetes who are taking statins, routine monitoring of liver function tests or muscle enzymes is not recommended except in specific circumstances.

The National Cholesterol Education Program revised their guidelinescite journal |author=Grundy SM, Cleeman JI, Merz CN, Brewer HB, Clark LT, Hunninghake DB, Pasternak RC, Smith SC, Stone NJ |title=Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III Guidelines |journal=J. Am. Coll. Cardiol. |volume=44 |issue=3 |pages=720–32 |year=2004 |pmid=15358046 |doi=10.1016/j.jacc.2004.07.001] ; however, their 2004 revisions have been criticized for use of nonrandomized, observational data.cite journal |author=Hayward RA, Hofer TP, Vijan S |title=Narrative review: lack of evidence for recommended low-density lipoprotein treatment targets: a solvable problem |journal=Ann. Intern. Med. |volume=145 |issue=7 |pages=520–30 |year=2006 |pmid=17015870 |doi=]

In the UK, the National Institute for Health and Clinical Excellence (NICE) has made recommendations for the treatment of elevated cholesterol levels, published in 2008. [NICE|67|Lipid modification|May 2008]

Alternative medicine

A [http://nccam.nih.gov/news/2004/052704.htm survey released in May 2004] by the National Center for Complementary and Alternative Medicine focused on who used complementary and alternative medicine (CAM), what was used, and why it was used in the United States by adults age 18 years and over during 2002. According to this survey, CAM was used to treat cholesterol by 1.1% of U.S. adults who used CAM during 2002 ( [http://nccam.nih.gov/news/report.pdf] table 3 on page 9). Consistent with previous studies, this study found that the majority of individuals (i.e., 54.9%) used CAM in conjunction with conventional medicine (page 6).

creening

Screening for a disease refers to testing for a disease, such as hypercholesterolemia, in 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 [http://www.ahrq.gov/clinic/uspstfix.htm U.S. Preventive Services Task Force (USPSTF)] has evaluated screening for hypercholesterolemia cite journal |author=Pignone M, Phillips C, Atkins D, Teutsch S, Mulrow C, Lohr K |title=Screening and treating adults for lipid disorders |journal=Am J Prev Med |volume=20 |issue=3 Suppl |pages=77–89 |year=2001 |pmid=11306236 | doi=10.1016/S0749-3797(01)00255-0] cite web |url=http://www.ahrq.gov/clinic/ajpmsuppl/lipidrr.htm |title=Screening for Lipid Disorders: Recommendations and Rationale |accessdate= |accessmonthday=Feb 26 |accessdaymonth = |accessyear=2007 |author=U.S. Preventive Services Task Force |last= |first= |authorlink= |coauthors= |date= |year= |month= |format= |work= |publisher= |pages= |language= |archiveurl= |archivedate= |quote= ] .

References

ee also

*Familial hypercholesterolemia