Metabolic syndrome is a combination of medical disorders that increase one's risk for cardiovascular disease and diabetes. It affects a large number of people in a clustered fashion. In some studies, the prevalence in the USA is calculated as being up to 25% of the population. A condition with some similarities to human metabolic syndrome is recognised in horses, see equine metabolic syndrome. It is unknown if they have the same etiology.
The metabolic syndrome is characterized by a group of metabolic risk factors in one person. They include:
* Abdominal obesity (excessive fat tissue in and around the abdomen)
* Atherogenic dyslipidemia (blood fat disorders — high triglycerides, low HDL cholesterol and high LDL cholesterol — that foster plaque buildups in artery walls)
* Elevated blood pressure
* Insulin resistance or glucose intolerance (the body can’t properly use insulin or blood sugar)
* Prothrombotic state (e.g., high fibrinogen or plasminogen activator inhibitor–1 in the blood)
* Proinflammatory state (e.g., elevated C-reactive protein in the blood)
People with the metabolic syndrome are at increased risk of coronary heart disease and other diseases related to plaque buildups in artery walls (e.g., stroke and peripheral vascular disease) and type 2 diabetes. The metabolic syndrome has become increasingly common in the United States. It’s estimated that over 50 million Americans have it.
The dominant underlying risk factors for this syndrome appear to be abdominal obesity and insulin resistance. Insulin resistance is a generalized metabolic disorder, in which the body can’t use insulin efficiently. This is why the metabolic syndrome is also called the insulin resistance syndrome.
Other conditions associated with the syndrome include physical inactivity, aging, hormonal imbalance and genetic predisposition.
Some people are genetically predisposed to insulin resistance. Acquired factors, such as excess body fat and physical inactivity, can elicit insulin resistance and the metabolic syndrome in these people. Most people with insulin resistance have abdominal obesity. The biologic mechanisms at the molecular level between insulin resistance and metabolic risk factors aren’t fully understood and appear to be complex.
How is the metabolic syndrome diagnosed?
There are no well-accepted criteria for diagnosing the metabolic syndrome. The criteria proposed by the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III), with minor modifications, are currently recommended and widely used.
The American Heart Association and the National Heart, Lung, and Blood Institute recommend that the metabolic syndrome be identified as the presence of three or more of these components:
* Elevated waist circumference:
Men — Equal to or greater than 40 inches (102 cm)
Women — Equal to or greater than 35 inches (88 cm)
Equal to or greater than 150 mg/dL
* Reduced HDL (“good”) cholesterol:
Men — Less than 40 mg/dL
Women — Less than 50 mg/dL
* Elevated blood pressure:
Equal to or greater than 130/85 mm Hg
* Elevated fasting glucose:
Equal to or greater than 100 mg/dL
AHA Recommendation for Managing the Metabolic Syndrome:
The primary goal of clinical management of the metabolic syndrome is to reduce the risk for cardiovascular disease and type 2 diabetes. Then, the first-line therapy is to reduce the major risk factors for cardiovascular disease: stop smoking and reduce LDL cholesterol, blood pressure and glucose levels to the recommended levels.
For managing both long- and short-term risk, lifestyle therapies are the first-line interventions to reduce the metabolic risk factors. These lifestyle interventions include:
* Weight loss to achieve a desirable weight (BMI less than 25 kg/m2)
* Increased physical activity, with a goal of at least 30 minutes of moderate-intensity activity on most days of the week
* Healthy eating habits that include reduced intake of saturated fat, trans fat and cholesterol
Metabolic syndrome is a cluster of conditions that occur together, increasing your risk of heart disease, stroke and diabetes.
Having just one of these conditions — increased blood pressure, elevated insulin levels, excess body fat around the waist or abnormal cholesterol levels — isn't diagnosed as metabolic syndrome, but it does contribute to your risk of serious disease. If more than one of these conditions occur in combination, your risk is even greater.
If you have metabolic syndrome or any of the components of metabolic syndrome, you have the opportunity to make aggressive lifestyle changes. Making these changes can delay or derail the development of serious diseases that may result from metabolic syndrome.
Research into the complex underlying process linking the group of conditions involved in metabolic syndrome is ongoing. As the name suggests, metabolic syndrome is tied to your body's metabolism, possibly to a condition called insulin resistance. Insulin is a hormone made by your pancreas that helps control the amount of sugar in your bloodstream.
Normally, your digestive system breaks down some of the foods you eat into sugar (glucose). Your blood carries the glucose to your body's tissues, where the cells use it as fuel. Glucose enters your cells with the help of insulin. In people with insulin resistance, cells don't respond normally to insulin, and glucose can't enter the cells as easily. Your body reacts by churning out more and more insulin to help glucose get into your cells. The result is higher than normal levels of both insulin and glucose in your blood.
Although perhaps not high enough to qualify as diabetes, an elevated glucose level still interferes with your body processes. Increased insulin raises your triglyceride level and other blood fat levels. It also interferes with how your kidneys work, leading to higher blood pressure. These combined effects of insulin resistance put you at risk of heart disease, stroke, diabetes and other conditions.
Combination of factors
Researchers are still learning what causes insulin resistance. It probably involves a variety of genetic and environmental factors. They think some people are genetically prone to insulin resistance, inheriting the tendency from their parents. But being overweight and inactive are major contributors.
Disagreement among experts
Not all experts agree on the definition of metabolic syndrome or whether it even exists as a distinct medical condition. Doctors have talked about this constellation of risk factors for years and have called it many names, including syndrome X and insulin resistance syndrome. Whatever it's called, and however it's precisely defined, this collection of risk factors is apparently becoming more prevalent.
The following factors increase your chances of having metabolic syndrome:
* Age. The prevalence of metabolic syndrome increases with age, affecting less than 10 percent of people in their 20s and 40 percent of people in their 60s. However, some research shows that about one in eight schoolchildren has three or more components of metabolic syndrome. And, other research has identified an association between childhood metabolic syndrome and adult cardiovascular disease decades later.
* Race. Hispanics and Asians seem to be at greater risk of metabolic syndrome than other races are.
* Obesity. A body mass index (BMI) — a measure of your percentage of body fat based on height and weight — greater than 25 increases your risk of metabolic syndrome. So does abdominal obesity — having an apple shape rather than a pear shape.
* History of diabetes. You're more likely to have metabolic syndrome if you have a family history of type 2 diabetes or a history of diabetes during pregnancy (gestational diabetes).
* Other diseases. A diagnosis of high blood pressure, cardiovascular disease or polycystic ovary syndrome — a similar type of metabolic problem that affects a woman's hormones and reproductive system — also increases your risk of metabolic syndrome.
Signs and symptoms
Having metabolic syndrome means you have several disorders related to your metabolism at the same time, including:
* Obesity, particularly around your waist (having an "apple shape")
* Elevated blood pressure
* An elevated level of the blood fat called triglycerides and a low level of high-density lipoprotein (HDL) cholesterol — the "good" cholesterol
* Resistance to insulin, a hormone that helps to regulate the amount of sugar in your body
Having one component of metabolic syndrome means you're more likely to have others. And the more components you have, the greater are the risks to your health.
What is metabolic syndrome?
An association between certain metabolic disorders and cardiovascular disease has been known since the 1940s. In the 1980s this association became more clearly defined and the term metabolic syndrome (also known as syndrome X or the dysmetabolic syndrome) was coined to designate a cluster of metabolic risk factors that come together in a single individual. In more current times, the term metabolic syndrome is found throughout medical literature and in the lay press as well. There are slight differences in the criteria of diagnosis - depending on which authority is quoted. Regardless, the concept of a clustering of risks leading to cardiovascular disease is well accepted.
The main features of metabolic syndrome include insulin resistance, hypertension (high blood pressure), cholesterol abnormalities, and an increased risk for clotting. Patients are most often overweight or obese.
Insulin resistance refers to the diminished ability of cells to respond to the action of insulin in promoting the transport of the sugar glucose, from blood into muscles and other tissues. Because of the central role that insulin resistance plays in the metabolic syndrome, a separate article is devoted to insulin resistance. Please see Insulin Resistance article for more information.
How is metabolic syndrome defined?
The definition of metabolic syndrome depends on which group of experts is doing the defining. Based on the guidelines from the 2001 National Cholesterol Education Program Adult Treatment Panel (ATP III), any three of the following traits in the same individual meet the criteria for the metabolic syndrome:
1. Abdominal obesity: a waist circumference over 102 cm (40 in) in men and over 88 cm (35 inches) in women.
2. Serum triglycerides 150 mg/dl or above.
3. HDL cholesterol 40mg/dl or lower in men and 50mg/dl or lower in women.
4. Blood pressure of 130/85 or more.
5. Fasting blood glucose of 110 mg/dl or above. (Some groups say 100mg/dl)
The World Health Organization (WHO) has slightly different criteria for the metabolic syndrome:
1. High insulin levels, an elevated fasting blood glucose or an elevated post meal glucose alone with at least 2 of the following criteria:
* Abdominal obesity as defined by a waist to hip ratio of greater than 0.9, a body mass index of at least 30 kg/m2 or a waist measurement over 37 inches.
2. Cholesterol panel showing a triglyceride level of at least 150 mg/dl or an HDL cholesterol lower than 35 mg/dl.
3. Blood pressure of 140/90 or above (or on treatment for high blood pressure).
How common is metabolic syndrome?
Metabolic syndrome is quite common. Approximately 20-30% of the population in industrialized countries have metabolic syndrome. By the year 2010, the metabolic syndrome is expected to affect 50-75 million people in the US alone.
What causes metabolic syndrome?
As is true with many medical conditions, genetics and the environment both play important roles in the development of the metabolic syndrome.
Genetic factors influence each individual component of the syndrome, and the syndrome itself. A family history that includes type 2 diabetes, hypertension, and early heart disease greatly increases the chance that an individual will develop the metabolic syndrome.
Environmental issues such as low activity level, sedentary lifestyle, and progressive weight gain also contribute significantly to the risk of developing the metabolic syndrome.
Metabolic syndrome is present in about 5% of people with normal body weight, 22% of those who are overweight and 60% of those considered obese. Adults who continue to gain 5 or more pounds per year raise their risk of developing metabolic syndrome by up to 45%.
While obesity itself is likely the greatest risk factor, others factors of concern include:
* women who are post-menopausal,
* eating an excessively high carbohydrate diet,
* lack of activity (even without weight change), and
* consuming an alcohol-free diet.
Why should I know about metabolic syndrome?
Metabolic syndrome is worth caring about because it is a condition that can pave the way to both diabetes and heart disease, two of the most common and important chronic diseases today.
Metabolic syndrome increases the risk of type 2 diabetes (the common type of diabetes) anywhere from 9-30 times over the normal population. That's a huge increase. As to the risk of heart disease, studies vary, but the metabolic syndrome appears to increase the risk 2-4 times that of the normal population.
There are other concerns as well that should be mentioned. Metabolic syndrome is associated with fat accumulation in the liver (fatty liver), resulting in inflammation and the potential for cirrhosis. The kidneys can also be affected, as there is an association with microalbuminuria -- the leaking of protein into the urine, a subtle but clear indication of kidney damage.
Other problems associated with metabolic syndrome include obstructive sleep apnea, polycystic ovary syndrome , increased risk of dementia with aging, and cognitive decline in the elderly.
How is metabolic syndrome treated?
The major goals are to treat both the underlying cause of the syndrome, and also to treat the cardiovascular risk factors if they persist. As has been discussed, the majority of people with metabolic syndrome are overweight and lead a sedentary lifestyle.
Lifestyle modification is the preferred treatment of metabolic syndrome. Weight reduction usually requires a specifically tailored multifaceted program that includes diet and exercise. Sometimes medications may be useful.
A detailed discussion of diet therapies, pros and cons of various diets etc. is beyond the scope of this article. However, there is now a trend toward the use of a Mediterranean diet -- one that is rich in “good” fats (olive oil) and contains a reasonable amount of carbohydrates and proteins (such as from fish and chicken).
The Mediterranean diet is palatable and easily sustained. In addition, recent studies have shown that when compared to a low fat diet, people on the Mediterranean diet have a greater decrease in body weight, and also had greater improvements in blood pressure, cholesterol levels, and other markers of heart disease -- all of which are important in evaluating and treating metabolic syndrome
A sustainable exercise program, fore example 30 minutes 5 days a week is reasonable to start, providing there is no medical contraindication. (If you have any special concerns in this regard, check with your doctor first.) There is a beneficial effect of exercise on blood pressure, cholesterol levels, and insulin sensitivity, regardless of whether weight loss is achieved or not. Thus, exercise in itself is a helpful tool in treating metabolic syndrome.
Cosmetic surgery to remove fat
Some people may ask: Why not just have liposuction of the abdomen and remove the large amount abdominal fat, which a big part of the problem? Data thus far shows no benefit in liposuction on insulin sensitivity, blood pressure, or cholesterol. As the saying goes, "If it's too good to be true, it probably is." Diet and exercise are still the preferred primary treatment of metabolic syndrome.
What if lifestyle changes are not enough to treat metabolic syndrome?
What if changes in lifestyle do not do the trick, what then? Drugs to control cholesterol levels, lipids, and high blood pressure may be considered.
If someone has already had a heart attack, their LDL (“bad”) cholesterol should be reduced below 100mg/dl. (Some experts now say it should be under 70mg/dl.) A person who has diabetes has a heart attack risk equivalent to that of someone who has already one and so should be treated in the same way. What remains controversial is whether metabolic syndrome should be considered a coronary equivalent or not. If you have metabolic syndrome, a detailed discussion about lipid therapy is needed between you and your doctor, as each individual is unique.
Blood pressure goals are generally set lower than 130/80. Some blood pressure medications offer more than simply lowering blood pressure. For example, a class of blood pressure drugs called ACE inhibitors has been found to also reduce the levels of insulin resistance and actually deter the development of type 2 diabetes. This is an important consideration when discussing the choice blood pressure drugs in the metabolic syndrome.
The discovery that a drug prescribed for one condition, and has other beneficial effects is not new. Drugs used to treat high blood sugar and insulin resistance may have beneficial effects on blood pressure and cholesterol profiles. A class of drugs called thiazolidinediones [pioglitazone (Actos) and rosiglitazone (Avandia)] also reduce the thickness of the walls of the carotid arteries.
Metformin (Glucophage), usually used to treat type 2 diabetes, also has been found to help prevent the onset of diabetes in people with metabolic syndrome. Indeed, in my practice, I routinely discuss metformin with my patients who have metabolic syndrome. Many of my patients who have insulin resistance associated with metabolic syndrome opt for metformin therapy. However, there are currently no established guidelines on treating metabolic syndrome patients with metformin if they do not have overt diabetes.
The term “metabolic syndrome” is a way of identifying individuals at high risk for the development of heart disease and diabetes. Intuitively we all know that obesity, high cholesterol, and hypertension are bad omens. We also know that insulin resistance precedes type 2 diabetes, and can itself be an important condition meriting treatment. Everyone reading this article knows someone who is overweight, hypertensive, or has cholesterol levels that are “a little high.” It may be a brother, sister, parent, neighbor, or even yourself.
For the physician, while the actual definition of "metabolic syndrome" may vary, the known clustering that occurs means that adults with any major cardiovascular risk should be evaluated for the presence of other risk factors. Patients at risk should receive education and counseling on lifestyle modification, and all risk factors for heart disease should be treated aggressively.
For the patient, the main point to understand is that it is important to treat the risk factors as bad things, before worse things happen. And while these changes can be addressed at a doctor's office, the other 99.999% of the time, they need to be addressed in the real world. We need to start having healthier food options readily available. We need to have time during the day to take a walk.
We basically need to restructure some fundamentals in our society. This author believes this has to happen, but it will take time. Until then, we each need to surround ourselves with people who support our goals and needs. We need to be aware of our own heath, and to make whatever changes we can to improve it.
The final take home message is:
* Find a walk buddy.
* Take a walk during your work break, even if it is just around the building.
* Go to a health food store.
* Look at what you feed your kids.
* Urge them to get outside and play.
It all adds up. Preventing metabolic syndrome really means having a healthy lifestyle.