It’s in the blood

11:00am Friday 5th September 2008

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In his latest article for our continuing Have A Heart campaign, Dr Robert Crook, a consultant cardiologist at York Hospital, examines the truth about cholesterol.

Cholesterol is one of the main types of fat in the blood. Its precise role is unclear, but high levels are well recognised to increase the risk of vascular disease such as heart attacks, strokes and furred up arteries in the legs.

There are two main types of cholesterol – Low Density Lipoprotein (LDL) and High Density Lipoprotein. Generally speaking, LDL is bad and potentially harmful, while HDL is regarded as good and cardio-protective.

The cholesterol level in any individual is dependant on a number of factors, including diet and lifestyle, but is largely determined by a person’s genes.

Cholesterol risks

It has long been recognised that the risks of developing (cardio) vascular disease is roughly proportional to the total blood level of cholesterol.

This relationship is more important if other risk factors are present, for example hypertension, diabetes and familial hypercholesterolaemia. While many people with vascular disease have raised cholesterol, only a minority of people with high cholesterol (and no other risk factors) go on to develop vascular disease.

Hence, the main gain in treating high cholesterol is in patients with established vascular disease or those people at risk of developing it such as diabetics, smokers, people with a positive family history of premature vascular disease, and high blood pressure.

Landmark trial

Until the late 1980s there was no satisfactory treatment for hypercholesterolaemia (high cholesterol level). While diet can reduce cholesterol in some people, there is little evidence that diet alone reduces the incidence of the consequences of vascular disease.

The 4S study (Scandinavian Simvastatin Survival Study) transformed the management of ischaemic heart disease. Published in 1994, it compared diet to diet plus Simvastatin (lipid regulating drug for lowering cholesterol) for five years in more than 4,444 patients with angina or previous heart attacks, and raised cholesterol.

There was an important reduction in death, risk of second heart attack and need for revascularisation with Simvastatin. The risk of death from heart attack was reduced by 42 per cent (ie there were 189 coronary deaths in patients on placebo vs 111 coronary deaths in patients on simvastatin). There was only one case of damage to the muscles which was reversible.

Subsequent trials

Since 4S, lipid lowering with statins has been the subject of a large number of trials, all of which have confirmed the benefit of statins, with overall a ten per cent reduction in cholesterol, resulting in a 20 per cent reduction in cardiac death and a similar reduction in myocardial infarction (heart attack). The efficiency of statins to prevent death or non-fatal stroke or MI yielded a NNT (number needed to treat) for statins of 11 in secondary prevention.

The evidence base for treatment, therefore, in patients with vascular disease, or those at risk of developing it, is overwhelming. Not only are statins effective, but they have few side-effects and a very good safety profile. In fact, statins are 1,000 times safer than aspirin.

Targets

Current recommendations are the subject of some controversy. The National Service Framework for Coronary Heart Disease has slightly different targets for treatment than the Joint British Society.

There is broad agreement that treatment for patients with established vascular disease (secondary prevention) should be aggressive. In any individual with vascular disease the total cholesterol should be lowered by 25 per cent, ideally to a total cholesterol of 4 (LDL 2).

For patients at risk the aim is at least a 20 per cent reduction, with a total cholesterol of five (LDL 3).

One could debate if the cholesterol should be measured at all if a person has no risk factors for vascular disease – the old World Health Organisation target was total cholesterol of 7.8.

Secondary hyperlipidaemia

Apart from genetics, poor diet, excess alcohol, some kidney diseases, hyperthyroidism and poorly controlled diabetes can all result in hypercholesterolaemia.

Non-drug method

Statins should always be used in combination with non-drug approachess.

A sensible low fat diet can help reduce your cholesterol and improve the LDL/HDL ratio. The department of nutrition and dietetics at York Hospital recommends the following general guidelines:

* reduction of fatty foods, particularly saturated fats such as fatty meats, lard, butter, cream, cheese, eggs, pastries, etc.

* encouraging a diet of fish, vegetables, fruit, soy protein, low glycaemic index foods (eg oats, pasta, lentils), soluble fibre (eg beans and oats), polyunsaturated fats (e.g. vegetable/sunflower oils, nuts, oily fish) and monounsaturated fats (eg olive oil).

* omega-3 fatty acids are available as tablets (Omacor) and have been shown to be beneficial post heart attack, particularly when dietary efforts with fatty fish fail.

* Flora Pro-Active (a plant sterol) and Benecol (a plant stanol) help reduce the absorption of cholesterol from the gut, and can be used as part of a cholesterol lowering diet.

* weight reduction if Body Mass Index is more than ideal.

* reduction in alcohol if more than recommended.

* low salt diet is also prudent for reducing blood pressure.

It is important to enjoy your food and be reassured that occasional indiscretions are allowed.

NICE

The National Institute for Clinical Excellence (NICE) has recently extended the recommendations for statin use. Anyone over 40 whose estimated risk of vascular disease (heart attack or stroke) is 20 per cent in the next ten years is eligible.

In particular, the importance of a family history of vascular disease has been recognised. So, for instance, if you have a first degree relative with premature (60 years of age) vascular disease, then you need a statin if your cholesterol is greater than five. This extension of the indications for statin treatment has been possible because Simvastatin has now come off patent and is now much cheaper than it was.

What should I do?

If you have angina or have had a previous heart attack or stroke, or furred-up arteries, or diabetes you will probably have had your cholesterol checked, treated and are being monitored. If you are over 40 years of age, you should see your GP for assessment. If you have a family history of premature vascular disease (in first degree relatives), high blood pressure or kidney disease you should have your cholesterol checked and treated (with a statin) if the total cholesterol is greater than five.

Statin treatment does not obviate the need for a sensible low fat diet, weight loss if required, regular exercise and not smoking.

Genetic mutation

While ischemic heart disease and high cholesterol can run in families and may be partly “genetic”, there is a specific condition called familial hypercholesterolaemia (FH) in which a specific genetic mutation results in very high cholesterol levels (typically more than ten) and a greatly increased risk of premature vascular disease. To date, this condition has not been actively screened for, but last week NICE released its recommendation (with attendant government funding) for a much more proactive process of screening and early treatment for those patients with FH. The reason for this new approach is partly as a result of a successful screening programme in Norway and also because successful treatment is now available. Conventional statins are rarely effective, but a new powerful statin (Rosuvastatin) used in combination with Ezitimibe often return the cholesterol to normal.

References

NICE (www.nice.org.uk) guidelines 48, 67 and 71.

H·E·A·R·T UK (cholestrol charity, www.heartuk.org.uk).