Heart attack - Risk factors

When talking about the risk factors for myocardial infarctionDeath of an area of heart muscle due to poor blood supply., more often called a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction., it is useful to distinguish between factors that you can change (often described as modifiable risk factors) and those that you cannot change (known as non-modifiable risk factors).

Heart attacks due to modifiable risk factors are potentially preventable. Even though you cannot change some risk factors, it's still important to be aware of them so that you know the importance of taking action to reduce your overall risk.[1]

In addition to 'traditional' risk factors that have been known for some time, such as smoking and high bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure, much is being learned about more recently identified risk factors.[2] This section will outline the following categories of risk factors:

Modifiable risk factors

One major international study looked at the impact of potentially modifiable risk factors on the risk of heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. in people in 52 different countries.

Factors that were found to increase someone's risk of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. included:[3]

  • Abnormal bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. lipids
  • Smoking (the more cigarettes smoked, the higher the risk of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.)
  • High blood pressure The pressure of blood within the arteries.(hypertensionHigh blood pressure.)
  • Type 2 diabetes mellitus (this condition has been shown to increase the risk of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. by two to five times compared with the risk in the general population)[3,4]
  • Abdominal obesityExcess accumulation of fat in the body. (when someone puts on excess weight around the waist area)
  • Psychological and social factors, such as stressRelating to injury or concern. and social isolation.

Factors found to protect against heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. included:[3]

  • Daily consumption of fruits and vegetables
  • Regular physical activity
  • Moderate alcohol intake (meaning three or more times a week).

These elements were found to be important in both men and women, of all ages and races, and in all parts of the world. Combined, these factors account for more than 90 per cent of someone's risk of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..[3]

Non-modifiable risk factors

Heart attack risk factors that cannot be modified include:[1,3]

  • Being older (atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow. becomes more common with increasing age)[5]
  • Being male (women before the menopauseThe time of a woman’s life when her ovaries stop releasing an egg (ovum) on a monthly cycle. are protected by the effects of oestrogenA hormone involved in female sexual development, produced by the ovaries. on the cardiovascular systemThe body system consisting of the heart and blood vessels.)
  • Having a family history of heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..
  • Being a member of certain races (for example, African-Americans and people of South Asian descent have much higher rates of heart disease than do Caucasians, partly due to higher rates of underlying conditions such as diabetes, obesityExcess accumulation of fat in the body. and high bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure)

While you cannot change these risk factors if you have them, it is important to know about them. This is because being aware that you may be at higher risk may give you more incentive to improve those risk factors that you can change, such as your diet and exercise habits.

Recently identified risk factors

Heart attacks often occur in people who do not have 'traditional' risk factors. Atherosclerosis is associated with inflammationThe body’s response to injury. throughout the arterial system, and it has been suggested that some inflammatory conditions may lead to a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction., even in people with normal coronaryRelating to the arteries supplying the heart itself. arteries. Such conditions may include systemic lupus erythematosisAn autoimmune, inflammatory condition. and myocarditisInflammation of the heart muscle..[1,6]

Other more recently discovered influences include:[2,7]

  • Gum disease
  • Sleep disorders such as snoring and sleep apnoea
  • Long-term exposure to noise
  • Cold weather
  • Infections
  • Pollutants and other toxic chemicals.

In addition, certain bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. chemicals that seem to be linked with inflammationThe body’s response to injury. and heart disease are helping doctors to identify other people who may also be at risk. These include: [2,7]

  • Lipoprotein(a) (a type of lipidOne of a group of compounds that are an important energy source. in the bloodstream that is similar to LDL-cholesterolSubstance that carries cholesterol around the bloodstream, a form of so-called 'bad cholesterol'.)
  • Total plasmaFluid in which the blood cells are suspended. homocysteineA type of amino acid (the building block of all proteins). (a bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. protein that is associated with early-onset atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow.. High levels may be reduced by maintaining a good intake of fruit and vegetables)
  • Factors that increase the tendency of the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. to clot, including a bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. clotting protein called fibrinogenA coagulation factor, a substance in the blood that brings about clotting.
  • Increased levels of high-sensitivity C-reactive proteinA protein found in the blood. Raised levels indicate inflammation, and can be used to estimate a person's risk of cardiovascular disease. (CRPAn abbreviation for C-reactive protein, found in the blood. Raised levels of this protein suggest tissue damage or necrosis (death of cells).; a protein in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. that indicates the presence of inflammationThe body’s response to injury.)

Other factors that may suggest an increased heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. risk are:

  • Increased thickness of the inner layer of the carotid arteriesThe two main arteries in the neck. - the arteries that carry bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. to the head and neck - known as carotid intima-media thicknessA measure of the thickness of the wall of the carotid artery.. This may be measured by ultrasound scan. It can be used to estimate the degree of atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow., which may indicate the likelihood of someone developing coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. disease[8]
  • Coronary arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. score (a measure of the amount of calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. in the coronaryRelating to the arteries supplying the heart itself. arteries, which indicates atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow. and is usually calculated using CTA scan that generates a series of cross-sectional X-ray images. scanning)[9]
  • Genetic factors.

However, further research is needed to learn just how important these different new risk factors are and to determine how good they are at predicting the risk of coronaryRelating to the arteries supplying the heart itself. problems.[3] The value of some of these factors is still disputed by some experts.[7]

References: 
  1. Longmore M, Wilkinson I and Török E. Oxford Handbook of Clinical Medicine 2002; 5th edition.
  2. Evaluating novel cardiovascular risk factors: can we better predict heart attacks? Ridker PM. Ann Intern Med 1999;130:933-7.
  3. Effect of potentially modifiable risk factors associated with myocardial infarctionDeath of an area of heart muscle due to poor blood supply. in 52 countries (the INTERHEART study): case-control study. Yusuf S, Hawken S, Ôunpuu S et al. Lancet 2004;364:937-52.
  4. Prevention and early detection of vascular complications of diabetes. Marshall SM and Flyvbjerg A. BMJ 2006;333:475-80.
  5. Subclinical atherosclerosisDisease leading to fatty deposits in the inner walls of the arteries, which reduce and may eventually obstruct blood flow.: what it is, what it means and what we can do about it. Toth PP. Int J Clin Pract 2008;62(8):1246-54.
  6. Myocardial infarction with angiographically normal coronaryRelating to the arteries supplying the heart itself. arteries. Chandrasekaran B and Kurbaan AS. J R Soc Med 2002;95:398-400.
  7. New cardiovascular risk determinants do exist and are clinically useful. Smulders YM, Thijs A, Twisk JW. Eur Heart J 2008;29:436-40.
  8. Carotid intima-media thickness at different sites: relation to incident myocardial infarctionDeath of an area of heart muscle due to poor blood supply.. The Rotterdam Study. Iglesias del Sol A, Bots ML, Grobbee DE et al. European Heart Journal 2002;23:934-40.
  9. Coronary arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. score combined with Framingham score for risk prediction in asymptomatic individuals. Greenland P, LaBree L, Azen SP et al. JAMA 2004;291:210-5.