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What is it?

Metabolic syndrome is a set of risk factors that includes: abdominal obesity, a decreased ability to process glucose (insulin resistance), dyslipidaemia, and hypertension. Patients who have this syndrome have been shown to be at an increased risk of developing cardiovascular disease and/or type 2 diabetes. Metabolic syndrome is a common condition that goes by many names (dysmetabolic syndrome, syndrome X, insulin resistance syndrome and obesity syndrome) but few outside the medical community have heard of it. Most patients have been educated about the importance of checking their cholesterol levels, watching for signs of diabetes, having their blood pressure monitored, and exercising – but there has been little to tie all of these factors together except pursuit of a 'healthier lifestyle'.

According to the AusDiab Study which was reported in 2012 found that the prevalence of the metabolic syndrome was 31.0% in Australia with an annual rate of occurrence of new cases in 2.6% of men and 1.7% of women. The rate of occurrence of new cases of the metabolic syndrome between the ages of 25 and 64 was higher in men than in women. However, after the age of 65 years, the rate of occurrence of new cases of the metabolic syndrome was higher in women than in men. The rate of occurrence of new cases was found to increase with age and with increasing waist circumference.

Various diagnostic criteria have been proposed by different organizations over the past twenty years

The World Health Organization (WHO) was the first to publish an internationally accepted definition for metabolic syndrome in 1998. Subsequently a number of other groups produced their own slightly different definitions.
In order to provide more consistency in both patient care and research, the International Diabetes Federation,  The National Heart, Lung and Blood Institute (NHLBI), the American Heart Association (AHA), World Heart Federation, and the International Association for the Study of Obesity published a joint statement in 2009 that describes a "harmonized" definition of metabolic syndrome which is widely used in Australia. The presence of any 3 of 5 risk factors listed below constitutes a diagnosis of metabolic syndrome.

Table 1. Criteria for clinical diagnosis of the metabolic syndrome according to the Joint Statement on the metabolic syndrome.

  • Elevated waist circumference- Population and country specifics (see Table 2).
  • Raised triglycerides  ≥1.7mmol/L (≥ 150 mg/dL) (or drug treatment for elevated triglycerides)
  • Fasting triglycerides greater than or equal to 1.69 mmol/L (150 mg/dL)
  • Reduced HDL cholesterol <1.0mmol/L (<40mg/dL) in men, <1.3mmol/L (<50mg/dL) in women.
  • Elevated blood pressure (or drug treatment for hypertension) ≥ 130 systolic or ≥85 diastolic.
  • Elevated Fasting glucose (fasting plasma glucose) ≥5.6 mmol/L (≥100mg/dL) or previously diagnosedd type 2 diabetes.

Table 2
Recommended threshold in waist circumference for abdominal obesity (high risk) 3,4,5     
Population Men Women
European/North American ≥102 cm ≥88 cm
Asian ≥90 cm ≥80 cm
Central and South American ≥90 cm ≥80 cm
Middle Eastern/Mediterranean ≥94 cm ≥80 cm
Sub-Saharan African ≥94 cm ≥80 cm


Also frequently seen with metabolic syndrome are prothrombotic (blood clotting) and proinflammatory tendencies. While these combined criteria and risk factors do not usually cause symptoms that are obvious to the affected person, they are a warning of an increased likelihood of clogged arteries, heart disease, stroke, diabetes, kidney disease, and even premature death. If left untreated, complications from untreated metabolic syndrome can develop in as few as 15 years. Those patients who have metabolic syndrome and also smoke tend to have an even poorer prognosis.

Another feature commonly present in metabolic syndrome but not included in the diagnostic criteria is hyperuricaemia (an increased level of uric acid in the blood). In many patients this does not cause any symptoms but excessive amounts of uric acid can be associated with gout.

The root cause of most cases of metabolic syndrome can be traced back to poor eating habits and a sedentary lifestyle. Some cases occur in those already diagnosed with hypertension and in those with poorly controlled diabetes; a few are thought to be linked to genetic factors that are still being studied.

All of the factors associated with metabolic syndrome are interrelated. Obesity and lack of exercise tend to lead to insulin resistance. Insulin resistance has a negative effect on lipid production, increasing VLDL (very low-density lipoprotein), LDL (low-density lipoprotein – the ‘bad’ cholesterol), and triglyceride levels in the bloodstream and decreasing HDL (high-density lipoprotein – the ‘good’ cholesterol). This can lead to fatty plaque deposits in the arteries which over time can lead to cardiovascular disease, blood clots and strokes. Insulin resistance also leads to increased insulin and glucose levels in the blood. Excess insulin increases sodium retention by the kidneys, which increases blood pressure and can lead to hypertension. Chronically elevated glucose levels in turn damage blood vessels and organs, such as the kidneys.
 

New References


1. (AusDiab) study - Baker Institute https://www.baker.edu.au/Assets/Files/Baker%20IDI%20Ausdiab%20Report_interactive_FINAL.pdf
2. Cameron AJ et al. The metabolic syndrome in Australia: prevalence using four definitions. Diabetes Res Clin Pract. 2007 Sep;77(3):471-8.
3. Alberti KG, Eckel RH, Grundy SM, et al. Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. Circulation. Oct 20 2009;120(16):1640-1645
4. RACGP - The metabolic syndrome https://www.racgp.org.au/afp/2013/august/the-metabolic-syndrome/
5. World Health Organization. Obesity: preventing and managing the global epidemic. Report on an WHO consultation. Geneva: WHO, 2000.


Last Review Date: October 25, 2018