KOLKATA: Cholesterol is a fat-like substance, found in the bloodstream as well as in bodily organs and nerve fibres.
Most cholesterol in the body is made by the liver from a wide variety of foods, especially from saturated fats, such as those found in animal products.
A diet high in saturated fat content, heredity, and various metabolic conditions such as diabetes mellitus influence an individual’s level of cholesterol.
According to World Health Organization (WHO), cholesterol levels usually rise steadily with age, more steeply in women, and stabilize after middle age.
Mean cholesterol levels vary moderately between regions, although never more than 2.0 mmol/l in any age group. Cholesterol is a key component in the development of atherosclerosis, the accumulation of fatty deposits on the inner lining of arteries.
Mainly as a result of this, cholesterol increases the risks of ischaemic heart disease, ischaemic stroke and other vascular diseases. Cholesterol is transported around the blood in ‘vehicles’ called lipoproteins.
There are two types of lipoproteins:
LDL (low density lipoprotein) is the ‘bad’ type of cholesterol. If there is too much LDL cholesterol in the blood, it can slowly build in the arteries, making them narrower which increases the risk of coronary heart diseases. HDL (high density lipoprotein) is the ‘good’ type of cholesterol.
It helps to remove excess cholesterol from the bloodstream and returns it to the liver where it is broken down and passed out of the body.
HDL consists of mostly protein. Its chief action seems to be to clear cholesterol from the body by picking up cholesterol from cells and carrying it back to the liver for disposal.
Low levels of HDL cholesterol increase the risk of coronary artery disease (CAD) and other forms of atherosclerotic disease.
High levels of HDL cholesterol appear to help protect against heart disease.
Increasing levels of LDL cholesterol in the blood are associated with an increased risk of atherosclerosis (hardening of the arteries), coronary heart disease (leading to angina and heart attacks) and stroke.
LDL cholesterol consists of mostly fat and about a quarter is protein, apo B, unlike other lipoproteins that have many (apo) proteins.
LDL carries cholesterol from the liver to other parts of the body where it is needed for cell repair and other activities. This lipoprotein tends to deposit its cholesterol part into artery walls and other body tissues such as tendons.
As with blood pressure, the risks of cholesterol are continuous and extend across almost all levels seen in different populations, even those with cholesterol levels much lower than those seen in North American and European populations.
High cholesterol is estimated to cause 18 per cent of global cerebrovascular disease (mostly nonfatal events) and 56 per cent of global ischaemic heart disease. Overall this amounts to about 4.4 million deaths (7.9 per cent of total) and 40.4 million DALYs (2.8 per cent of total).
Of this total disease burden, 27 per cent occurred in SEAR-D, 18 per cent in EUR-C and 11 per cent in WPR-B. In AMR-A and Europe, 5?12 per cent of DALYs were attributable to suboptimal cholesterol levels. In most regions, the proportion of female deaths attributable to cholesterol is slightly higher than that for men.
Lowering total serum cholesterol levels is an ideal strategy for reducing the burden of cardiovascular disease. Potent, safe and highly effective cholesterol-lowering medication is available in the form of statins, and there are many low-cost methods for identifying those who need to lower their serum cholesterol.
Modelling studies suggest that lowering total serum cholesterol, either by treating elevated total serum cholesterol alone or by managing multiple risk factors, is cost-effective in many low- and middle-income countries. While the use of cholesterol-lowering medication is considered important in reducing the burden of cardiovascular disease, differences in the way various health systems are implementing this strategy are not well understood.
Comparing individual studies is difficult because the definition of a high blood cholesterol level varies among studies and, until recently, population-wide data has been lacking for many places.
The growing number of national health examination surveys that measure total serum cholesterol provides an opportunity to ascertain how well cholesterol-lowering medication is being delivered to populations at risk of cardiovascular disease. (AGENCIES)
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