Risk factors

In the 1960s, the investigators of the Framingham Heart Study, USA, coined the term ‘risk factors’ for the development of cardiovascular disease (CVD).1,2 They found that smoking, high cholesterol level, blood pressure and electrocardiogram abnormalities all increased the risk of CVD. In the following years, other risk factors were identified: physical inactivity, obesity, diabetes, psychosocial factors and isolated systolic hypertension. The data from the Framingham study provided a firm basis upon which further studies, such as the WHO MONICA project3 and the INTERHEART study4, could build, so that we now have a good understanding of cardiovascular risk factors.

Risk factors can be classified as non-modifiable (e.g. genetic makeup) or modifiable (e.g. diet, cholesterol levels). In order to minimise the risk of myocardial infarction, modifiable risk factors should be identified and managed appropriately.5

Major modifiable and non-modifiable risk factors for cardiovascular disease

Major  modifiable  and  non  modifiable  risk  factors  for  cardiovascular  disease             physical, clinical history and genetic makeup as risk factors for cardiovascular disease

Of course, these factors are often interrelated and rarely occur alone.

Risk factors for ischaemic heart disease rarely occur alone6

Risk  factors  for  ischaemic  heart  disease  rarely  occur  alone    Interplay between different risk factors determine the clinical course of ischaemic heart diseases

Increasing age

Older adults are more likely to die of heart disease than younger patients. Interestingly, slightly more myocardial infarctions occur in patients aged below 60 years than those over 60 years (53.2% vs. 46.8% respectively). However, when separated into male and female cases, the risk is much more for women over 60 years than for those below 60 years (32.3% vs. 67.7%), so it is difficult to separate the risk of age and gender from each other.7

Gender

Men have a higher risk of cardiovascular disease than women. The risk increases for women after the menopause, but only nears the risk for men in around the eighth decade.5,7,8

Genetic factors

The risk of cardiovascular disease is increased in individuals with a first-degree relative who has had coronary heart disease or stroke below the age of 55 years (for males) or 65 years (for females).8

Genetic variations can also affect cardiac function, blood coagulation, and lipid metabolism, or increase the risk of hypertension, diabetes, obesity, and smoking addiction.9

Racial and ethnic background

The risk of cardiovascular disease is increased in South Asians and American Blacks compared with White. African Americans are more likely to have severe high blood pressure, which is associated with heart disease. The other ethnic groups that are at increased risk have higher rates of obesity and diabetes, which are associated with heart disease.8

The INTERHEART study4 identified 9 major modifiable risk factors were responsible for more than 90% of the risk of an acute myocardial infarction, regardless of gender, ethnicity, or geographic region. The risk factors included:

  1. Smoking
  2. Abnormal blood lipids
  3. Hypertension
  4. Diabetes
  5. Abdominal obesity
  6. Psychosocial factors
  7. Low physical activity level
  8. Poor fruit/vegetable consumption
  9. Poor alcohol consumption

Smoking and second-hand smoke

Smoking cigarettes presents one of the highest risks worldwide for acute myocardial infarction. The INTERHEART study showed the increase in risk to be directly proportional to the amount of cigarettes smoked, with no upper limit.4

While not as bad as smoking cigarettes, smoking other products or inhaling second-hand smoke still increases the risk of heart disease and myocardial infarction.

Abnormal blood lipids

Abnormalities of blood lipids are directly related to the increase in risk of acute myocardial infarction, with no upper threshold. In particular, the ApoB/ApoB1 ratio seems to be the most important indicator of risk across different populations.4

Hypertension

Hypertension is responsible for the greatest number of overall cardiovascular deaths. With respect to the risk of acute myocardial infarction, hypertension carries a risk similar to diabetes, obesity, and psychosocial factors, and is only superseded by smoking and abnormal lipids.4

Diabetes mellitus

Diabetes mellitus is a metabolic disease in which the body does not produce or effectively use insulin. Even if blood sugar is well controlled, people with diabetes are at increased risk of cardiovascular disease.4,5

Abdominal obesity

Even without other risk factors, obesity or being overweight increases the risk of heart disease. The risk is more closely related to the waist/hip ratio than to the body mass index.4 In addition, obesity increases the likelihood of developing high blood pressure, high cholesterol and diabetes, which are also risk factors for heart disease.

Psychosocial factors

Psychosocial factors, such as depression, stress (including financial stress) and life events, are associated with a high risk of acute myocardial infarction.4

Lifestyle

Regular moderate to intense exercise, daily consumption of fruit or vegetables, and consumption of alcohol three or more times a week, all served to decrease the risk of acute myocardial infarction.4

Other factors

Although the rate of cardiovascular disease may be higher in developed or wealthy countries, the mortality rates for these diseases are still much higher in poorer countries. This is due to less effective healthcare and prevention in these less-developed countries as well as the fact that in wealthier countries people live longer – allowing more time for cardiovascular disease to develop.5

References: 
  1. Dawber TR. The Framingham Study: The epidemiology of atherosclerotic disease. Cambridge, MA, Harvard University Press, 1980.
  2. Mendis S. The contribution of the Framingham Heart Study to the prevention of cardiovascular disease: A global perspective. Progress in Cardiovascular Diseases 2010;53(1):10-14.
  3. Tunstall-Pedoe H, ed. World largest study of heart disease, stroke, risk factors and population trends, 1979-2002. MONICA Monograph and Multimedia Sourcebook, MONICA Project. Geneva, World Health Organization, 2003.
  4. Yusuf S et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): Case-control study. Lancet 2004;364(9438):937-952.
  5. Mendis S, Puska P, Norrving B, editors. Global Atlas on Cardiovascular Disease Prevention and Control. World Health Organization, Geneva 2011.
  6. World Health Organization. Global health risks: Mortality and burden of disease attributable to selected major risks. WHO, Geneva, 2009.
  7. Anand S, et al, on behalf of the INTERHEART Investigators. Eur Heart J 2008;29:932-940.
  8. McKay J, Mensah G. The atlas of heart disease and stroke. Risk Factors. CDC 2009. Available online at: http://www.who.int/cardiovascular_diseases/resources/atlas/en/ Accessed January 2013.
  9. Schunkert H, et al. Genetics of myocardial infarction: a progress report. Eur Heart J 2010;31:918-925.
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