SEARCH

SEARCH BY CITATION

Keywords:

  • metabolic syndrome;
  • population surveillance;
  • public health surveillance;
  • risk factors

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Background:  Recently, a Joint Scientific Statement bridged differences between previous definitions of metabolic syndrome. Our objective was to estimate the prevalence of metabolic syndrome in a representative sample of US adults and to examine its correlates.

Methods:  We analyzed data for up to 3461 participants aged ≥20 years of the 2003–2006 National Health and Nutrition Examination Survey.

Results:  Using waist circumference thresholds of ≥102 cm for men and ≥88 cm for women, the age-adjusted prevalence of metabolic syndrome was 34.3% among all adults, 36.1% among men, and 32.4% among women. Using racial- or ethnic-specific International Diabetes Federation criteria for waist circumference, the age-adjusted prevalence of metabolic syndrome was 38.5% for all participants, 41.9% for men, and 35.0% for women. Prevalence increased with age, peaking among those aged 60–69 years. Prevalence was lower among African American men than White or Mexican American men, and lower among White women than among African American or Mexican American women. In a multivariate regression model, significant independent associations were noted for age (positive), gender (men higher than women), race or ethnicity (African Americans and participants of another race lower than Whites), educational status (inverse), hypercholesterolemia (positive), concentrations of C-reactive protein (positive), leisure time physical activity (inverse), microalbuminuria (positive), and hyperinsulinemia (positive). Additional adjustment for body mass index weakened many of the associations, with educational status and microalbuminuria no longer significant contributors to the model.

Conclusion:  Metabolic syndrome continues to be highly prevalent among adults in the US.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Metabolic syndrome remains a subject of considerable interest because of the large number of people who have clustering of cardiometabolic factors and because of the increased risk for diabetes and cardiovascular disease.1,2 First given a definition by the World Health Organization in 1998,3 metabolic syndrome has been variously defined by major public health and professional organizations (Table 1).4–10 Recently, an attempt was made to bridge the differences between two of the most commonly used definitions,11 namely that published by the American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI) in 200510 and that published by the International Diabetes Federation (IDF).9

Table 1.   Definitions of metabolic syndrome*
 WHO 19983WHO 19994EGIR 19995NCEP 20016NHLBI/AHA 20048AHA/NHLBI 200510IDF 20059Harmonizing definition 200911
  1. *The definition of the American Association of Clinical Endocrinologists has not been included because of complex criteria.7

  2. ACR, albumin:creatinine ratio; AHA, American Heart Association; DBP, diastolic blood pressure; DM, diabetes mellitus; EGIR, European Group for the Study of Insulin Resistance; FPG, fasting plasma glucose; HDL-C, high-density lipoprotein–cholesterol; IDF, International Diabetes Federation; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; IR, insulin resistance; NCEP, National Cholesterol Education Program; NHLBI, National Heart, Lung, and Blood Institute; SBP, systolic blood pressure; T2DM, Type 2 diabetes mellitus; TG, triglycerides; UAER, urinary albumin excretion rate; WC, waist circumference; WHO, World Health Organization; WHR, waist:hip ratio.

GlucoseDM, IGT, or IFG as per WHO criteriaDM, IGT, or IFG as per WHO criteriaFPG ≥ 110 mg/dLFPG ≥ 110 mg/dLFPG ≥ 100 mg/dLFPG ≥ 100 mg/dL or treatmentFPG ≥ 100 mg/dL or previously diagnosed T2DMFPG ≥ 100 mg/dL or treatment
Insulin resistanceGlucose uptake below lowest quartileGlucose uptake below lowest quartileIR or fasting hyperinsulinemia (top 25%)
Blood pressureSBP ≥ 160, DBP ≥ 90 mmHgSBP ≥ 140, DBP ≥ 90 mmHgSBP ≥ 140, DBP ≥ 90 mmHg or treatmentSBP ≥ 130, DBP ≥ 85 mmHgSBP ≥ 130, DBP ≥ 85 mmHgSBP ≥ 130, DBP ≥ 85 mmHg or treatmentSBP ≥ 130, DBP ≥ 85 mmHg or treatmentSBP ≥ 130, DBP ≥ 85 mmHg or treatment
DyslipidemiaTG ≥ 150 mg/dL and/or HDL-C < 35 mg/dL in men, <39 mg/dL in womenTG ≥ 150 mg/dL and/or HDL-C < 35 mg/dL in men, <39 mg/dL in womenTG > 177 mg/dL or HDL-C < 39 mg/dL or treatment
TriglyceridesTG ≥ 150 mg/dLTG ≥ 150 mg/dLTG ≥ 150 mg/dL or treatmentTG ≥ 150 mg/dL or treatmentTG ≥ 150 mg/dL or treatment
HDL-CHDL-C < 40 mg/dL in men, <50 mg/dL in womenHDL-C < 40 mg/dL in men, <50 mg/dL in womenHDL-C < 40 mg/dL in men, <50 mg/dL in women or treatmentHDL-C < 40 mg/dL in men, <50 mg/dL in women or treatmentHDL-C < 40 mg/dL in men, <50 mg/dL in women or treatment
AnthropometryWHR > 0.90 in men, >0.85 in women and/or BMI >30 kg/m2WHR > 0.90 in men, >0.85 in women and/or BMI >30 kg/m2WC ≥ 94 cm in men, ≥80 cm in womenWC > 102 cm in men, >88 cm in womenWC > 102 cm in men, >88 cm in womenWC ≥ 102 cm in men, ≥88 cm in women; Asian Americans: ≥90 cm in men, ≥80 cm in womenCentral obesity: ethnic specificWC: population and country specific
MicroalbuminuriaUAER ≥ 20 μg/min or ACR ≥ 20 mg/gUAER ≥ 20 μg/min or ACR ≥ 30 mg/g
DefinitionGlucose intolerance, IGT, or DM and/or IR plus ≥2 other componentsGlucose intolerance, IGT, or DM and/or IR plus ≥2 other componentsIR or fasting hyperinsulinemia plus ≥2 other components≥3 of 5 components≥3 of 5 components≥3 of 5 componentsCentral obesity plus ≥2 of another 4 components≥3 of 5 components
Includes people with diabetes?YesYesNoYesYesYesYesYes

In 2001, the National Cholesterol Education Program (NCEP) approached the definition of metabolic syndrome by including five factors (waist circumference, triglycerides, high-density lipoprotein–cholesterol (HDL-C), blood pressure, and glucose), establishing a threshold for each factor, and conferring the presence of the syndrome if a person had any three of the five factors.6 Using the same five factors, the IDF focused on abdominal obesity as the key factor underlying metabolic syndrome, making its presence mandatory.9 The presence of abdominal obesity plus two or more other abnormalities constituted metabolic syndrome.9

The new joint definition11 maintains the same five factors and thresholds for four of the five factors, but eliminates the IDF requirement for the presence of abdominal obesity, opting instead to adhere to the algorithm of three or more abnormalities of the five originally presented by NCEP in 2001. One of the major distinctions between the two older definitions was the choice of threshold values for abdominal obesity. In addition to ethnic-specific thresholds, the new Joint Scientific Statement now also provides for country-specific thresholds.11 The aims of the present study were to provide updated estimates of the prevalence of metabolic syndrome among adults in the US using the guidelines of the 2009 Joint Scientific Statement,11 to examine the impact of using different thresholds for abdominal obesity on the prevalence of metabolic syndrome, and to study some of the correlates of the syndrome.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

In the present study, we used data from the National Health and Nutrition Examination Survey (NHANES) 2003–2006.12 Participants were recruited using a multistage, stratified sampling design consisting of four stages of selection: (i) counties or small groups of contiguous counties; (ii) a block or group of blocks containing a cluster of households; (iii) households; and (iv) one or more participants from households. Because of the differential probabilities of selection, sampling weights were created that reflected the base probabilities of selection, adjustment for non-response, and post-stratification. Participants were interviewed at home and were invited to attend a mobile examination center, where they were asked to complete additional questionnaires, to undergo various examinations, and to provide a blood sample. The study received human subjects approval, and participants were asked to sign an informed consent form.

Metabolic syndrome was defined using the definition presented in the 2009 Joint Scientific Statement (Table 1).11 Waist circumference was measured at the high point of the iliac crest at minimal respiration to the nearest 0.1 cm. Serum triglyceride concentrations were measured enzymatically after hydrolyzation to glycerol, and HDL-C was measured following the precipitation of other lipoproteins with a heparin–manganese chloride mixture. Plasma glucose concentrations were determined using an enzymatic reaction. Up to four attempts were made to collect three blood pressure readings in the mobile examination center. For participants who had three measurements, the average of the last two measures of blood pressure was used; for participants with only two measurements, the last measurement was used, and for participants who had one measurement, that single measurement was used to establish high blood pressure status.

The new definition for metabolic syndrome does not use a single set of criteria for waist circumference. Rather, the definition allows for criteria that are population and country specific. In the US, the 2001 NCEP definition originally set the criteria as >102 cm in men and >88 cm in women.6 These thresholds evolved to ≥102 cm in men and ≥88 cm in women in 2005 (≥94 cm in men and ≥80 cm in women for Asians living in the US).10 Because the IDF embraced waist circumference thresholds for racial and ethnic groups that were considerably lower than ≥102 cm in men and ≥88 cm in women, we created three variables for metabolic syndrome that differed only in the application of criteria for waist circumference to examine their impact on prevalence and associations. We defined metabolic syndrome once using a waist circumference of ≥102 cm in men and ≥88 cm in women. We defined metabolic syndrome a second time using a waist circumference of ≥102 cm in men and ≥88 cm in women for participants who were White, African American, or of another race and a waist circumference of ≥90 cm in men and ≥80 cm in women for participants who were Mexican American or another Hispanic ethnicity. Finally, we defined metabolic syndrome a third time using the IDF criteria for waist circumference, namely ≥94 cm in men who were White, African American, or another race or ethnicity, ≥90 cm in men who were Mexican American or of another Hispanic ethnicity, and ≥80 cm in women.

Major covariates included age, gender, race or ethnicity (White, African American, Mexican American, other Hispanic, other and mixed race), educational status (<high school, high school graduate, >high school), smoking status (never, former, current), blood pressure status, hypercholesterolemia, body mass index (BMI), leisure time physical activity, glycemic status, estimated glomerular filtration rate (GFR), urinary albumin creatinine ratio, C-reactive protein (CRP) concentrations, insulin concentrations, and histories of congestive heart failure, coronary heart disease, angina pectoris, heart attack, and stroke. In addition, we also examined concentrations of HbA1c, low-density lipoprotein–cholesterol (LDL-C), alanine transaminase, aspartate aminotransferase, alkaline phosphatase, γ-glutamyltransferase, lactic dehydrogenase, uric acid, potassium, albumin, and globulin, as well as white blood cell counts. Participants who had smoked at least 100 cigarettes during their lifetime and were currently smoking were designated as current smokers. Those who had smoked at least 100 cigarettes during their lifetime and were not currently smoking were designated as former smokers. Those who had not smoked at least 100 cigarettes during their lifetime were designated as never having smoked. Three levels of blood pressure status were included: normal [systolic blood pressure (SBP) <120 mmHg and diastolic blood pressure (DBP) <80 mmHg], prehypertension (SBP 120–139 mmHg or DBP 80–89 mmHg), and hypertension (SBP ≥140 mmHg or DBP ≥90 mmHg or self-reported current use of antihypertensive medication). The BMI (kg/m2) was calculated from measured weight and height. Serum concentrations of total cholesterol were measured enzymatically using the Roche Hitachi 717 and 912 instruments (Roche Diagnostics, Indianapolis, IN, USA). Hypercholesterolemia was defined as a concentration ≥200 mg/dL or the self-reported current use of cholesterol-lowering medications. To estimate leisure time physical activity, we calculated the number of minutes per week of moderate and vigorous leisure time physical activity, summed the number of moderate minutes and vigorous minutes multiplied by two, and dichotomized those times into ≥150 or <150 min/week.13 Four levels of glycemic status were created: normoglycemia, impaired fasting glucose (fasting plasma glucose (FPG) 100–125 mg/dL), undiagnosed diabetes (FPG ≥ 126 mg/dL), and previously diagnosed diabetes based on self-reported information. The estimated GFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration equations.14 Urinary albumin was measured by a solid-phase fluorescent immunoassay, whereas urinary creatinine was measured by a Jaffé rate reaction. Concentrations of CRP were determined by latex-enhanced nephelometry on a Behring Nephelometer (Siemens Healthcare Diagnostics, Deerfield, IL, USA). For the 2003–2004 cycle, concentrations of insulin were measured by the Tosoh AIA-PACK IRI (Tosoh Bioscience, South San Francisco, CA, USA), an immunoenzymometric assay, at the University of Missouri-Columbia (Columbia, MO, USA). For the 2005–2006 cycle, insulin concentrations were measured using the Mercodia Insulin ELISA assay (Mercodia, Winston Salem, NC, USA) at the Fairview Medical Center Laboratory (University of Minnesota, Minneapolis, MN, USA). Based on the results of a cross-over study, regression equations were developed to convert values from one method to those of the other method. The presence of a history of congestive heart failure, coronary heart disease, angina pectoris, heart attack, and stroke was determined from a series of questions posed to participants about whether they had ever been told by a doctor or other health professional that they had one of those conditions.

The analyses were limited to men and non-pregnant women aged ≥20 years who attended the morning examination and had fasted at least 8 h. Age adjustment was performed by the direct method using the projected year 2000 US population. Differences in percentages and means were calculated using Chi-squared tests and t-tests, respectively. Prevalence ratios using the log-binomial method were calculated to assess the independent association between the presence of metabolic syndrome (dependent variable) and various covariates. sudaan (Software for the Statistical Analysis of Correlated Data; Research Triangle Institute, Research Triangle Park, NC, USA) was used for analyses to account for the complex sampling design.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

A total of 3959 participants aged ≥20 years attended the morning examination. Excluding pregnant women reduced the number to 3723. Complete data for all components of metabolic syndrome to calculate the prevalence of metabolic syndrome by age groups, gender, and race or ethnicity were available for 3461 participants. Additional losses of sample size occurred for analyses involving covariates.

The age-adjusted prevalence of metabolic syndrome was 34.3% when the 102/88 cm thresholds for waist circumference were used and 35% when thresholds for waist circumference of 90/80 cm for Mexican Americans and other Hispanics were used (Table 2). Using the IDF thresholds for waist circumference boosted the prevalence of metabolic syndrome to 38.5%. Using the definition that used waist circumference thresholds of 102 cm for men and 88 cm for women, the age-adjusted prevalence was 3.7% higher among men than women (= 0.063) and was lower among African American men than White (< 0.001) and Mexican American (= 0.010) men and lower among White women than African American (= 0.034) and Mexican American (= 0.004) women. Prevalence reached a peak among both men and women aged 60–69 years, except among women when the definition that used IDF criteria for waist circumference was used.

Table 2.   Age-adjusted and age-specific prevalence of the metabolic syndrome among US adults aged ≥20 years, National Health and Nutrition Examination Survey 2003–2006
 nMetabolic syndrome*Metabolic syndromeMetabolic syndrome
  1. Data show prevalence as a percentage, with the SE in parentheses.

  2. *Metabolic syndrome was defined using waist circumference (WC) criteria of ≥102 cm in men and ≥88 in women.

  3. Metabolic syndrome was defined using WC criteria of ≥102 cm in men and ≥88 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

  4. Metabolic syndrome was defined using WC criteria of ≥94 cm in men and ≥80 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

Total346134.3 (1.2)35.0 (1.1)38.5 (1.1)
Men180336.1 (1.4)37.3 (1.3)41.9 (1.3)
Women165832.4 (1.6)32.6 (1.6)35.0 (1.6)
Men
 20–29 years31715.0 (2.6)17.5 (2.6)19.8 (2.9)
 30–39 years29127.8 (3.0)29.3 (3.1)33.0 (2.9)
 40–49 years31139.5 (2.4)40.6 (2.4)45.9 (2.6)
 50–59 years23644.6 (3.5)45.5 (3.4)49.5 (3.2)
 60–69 years28559.3 (4.2)60.1 (4.1)67.3 (4.1)
 ≥70 years36344.9 (3.3)45.2 (3.3)51.9 (2.9)
 White97638.4 (1.7)38.4 (1.7)43.2 (1.7)
 African American34525.5 (1.9)25.5 (1.9)32.5 (2.5)
 Mexican American36434.4 (2.9)44.5 (2.8)44.5 (2.8)
Women
 20–29 years24513.7 (2.3)14.0 (2.3)15.0 (2.4)
 30–39 years27016.9 (2.3)16.9 (2.3)17.5 (2.6)
 40–49 years30631.8 (2.7)31.9 (2.7)33.4 (2.8)
 50–59 years23743.3 (4.7)43.3 (4.7)46.2 (4.3)
 60–69 years29055.4 (3.6)55.4 (3.6)57.6 (3.7)
 ≥70 years31054.5 (2.8)54.8 (2.8)63.5 (2.5)
 White85931.3 (2.3)31.3 (2.3)33.8 (2.3)
 African American35238.2 (2.0)38.2 (2.0)41.1 (2.1)
 Mexican American31641.9 (2.0)44.1 (1.8)44.1 (1.8)

Among all participants, 21.2% had no cardiometabolic abnormalities and 4.4% had five cardiometabolic abnormalities (Table 3). Using the definition of metabolic syndrome that was based on waist circumference thresholds of 102/88 cm, 88% of participants with metabolic syndrome had abdominal obesity (men 81%; women 96.7%), 69.6% had hypertriglyceridemia (men 72.8%; women 65.9%), 59% had low HDL-C (men 54%; women 65.3%), 50.3% had elevated blood pressure (men 52.7%; women 45.9%), and 68.9% had hyperglycemia (men 71.7%; women 65.2%).

Table 3.   Age-adjusted and age-specific distribution of the number of metabolic syndrome components among US adults aged ≥20 years, National Health and Nutrition Examination Survey 2003–2006
 nNumber of components
012345
  1. Data show prevalence as a percentage, with the SE in parentheses.

  2. *Estimate does not meet the standard of statistical reliability and precision (relative SE >30%).

Total346121.2 (1.0)22.9 (0.7)21.6 (0.8)19.2 (0.9)10.6 (0.6)4.4 (0.4)
Men180319.2 (1.3)23.1 (1.3)21.6 (1.1)20.2 (1.2)11.4 (1.0)4.4 (0.6)
Women165823.2 (1.4)22.9 (1.1)21.5 (1.2)18.2 (1.1)9.9 (0.9)4.4 (0.6)
Men
 20–29 years31737.6 (3.8)27.4 (2.7)20.0 (2.5)11.1 (2.2)3.5 (1.1)*0.4 (0.3)*
 30–39 years29125.9 (2.9)26.8 (1.7)19.5 (2.4)17.4 (2.4)7.8 (1.8)2.6 (1.1)*
 40–49 years31117.7 (2.6)23.4 (3.2)19.4 (3.0)20.3 (2.3)14.0 (2.4)5.3 (1.1)
 50–59 years23612.5 (2.3)20.4 (2.5)22.4 (2.7)24.8 (3.8)14.8 (3.4)5.1 (1.4)
 60–69 years2852.3 (0.9)*16.9 (3.1)21.5 (3.0)30.8 (3.6)17.5 (3.1)11.0 (2.5)
 ≥70 years3636.0 (1.4)18.7 (2.1)30.4 (3.0)23.9 (2.7)15.3 (1.9)5.7 (1.4)
 White97619.3 (1.7)22.4 (1.6)19.9 (1.4)21.5 (1.5)12.2 (1.3)4.8 (0.8)
 African American34523.6 (2.0)24.3 (1.8)26.5 (2.0)17.1 (1.6)6.2 (1.1)2.3 (0.9)*
 Mexican American36415.2 (2.3)28.8 (3.0)21.6 (2.6)18.4 (2.2)11.4 (2.0)4.5 (1.5)*
Women
 20–29 years24541.2 (3.5)28.7 (2.9)16.4 (2.5)10.8 (2.3)2.2 (0.9)*0.6 (0.6)*
 30–39 years27032.2 (3.8)29.9 (3.3)21.0 (3.2)12.2 (1.9)4.1 (1.5)*0.7 (0.5)*
 40–49 years30623.2 (2.5)21.6 (2.9)23.3 (3.0)17.5 (1.9)11.0 (2.1)3.4 (1.3)*
 50–59 years23715.3 (1.8)18.7 (2.6)22.7 (4.1)22.5 (3.3)12.6 (2.4)8.1 (2.3)
 60–69 years2906.9 (1.9)19.6 (2.8)18.1 (2.7)26.1 (2.6)21.2 (2.7)8.1 (2.1)
 ≥70 years3105.2 (1.4)12.6 (2.7)27.7 (2.4)28.5 (3.0)16.2 (2.4)9.9 (1.6)
 White85925.9 (1.8)22.8 (1.6)19.9 (1.6)17.2 (1.5)9.9 (1.3)4.3 (0.6)
 African American35211.8 (1.7)22.4 (2.5)27.6 (3.1)25.1 (1.7)10.0 (1.5)3.1 (0.7)
 Mexican American31611.5 (2.1)20.1 (1.8)26.4 (1.8)21.8 (2.4)13.9 (2.2)6.3 (1.3)

The age-adjusted and age-specific prevalence of the components of metabolic syndrome according to age group, gender, and race or ethnicity are presented in Table 4. Some noteworthy findings include that 92.5% of Mexican American women had abdominal obesity when a threshold of 80 cm was used, 47.2% of African American women had elevated blood pressure, and 50.1% of Mexican American men had hyperglycemia. Furthermore, the prevalence of hypertriglyceridemia was lowest among African American participants compared with White or Mexican American participants. In addition, a lower percentage of African American men had low levels of HDL-C than White or Mexican American men. However, similar percentages of White and African American women had low HDL-C levels. The percentages of abdominal obesity, elevated blood pressure, and hyperglycemia were very high at advanced ages.

Table 4.   Age-adjusted and age-specific prevalence of components of the metabolic syndrome among US adults aged ≥20 years, National Health and Nutrition Examination Survey 2003–2006
 nAbdominal obesity*Abdominal obesityAbdominal obesityHypertri-glyceridemiaLow HDL-CElevated blood pressureHyperglycemia
%SE%SE%SE%SE%SE%SE%SE
  1. *Waist circumference criteria of ≥102 cm in men and ≥88 in women.

  2. Waist circumference criteria of ≥102 cm in men and ≥88 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

  3. Waist circumference criteria of ≥94 cm in men and ≥80 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

  4. LDL-C, low-density lipoprotein–cholesterol.

Total346153.61.256.81.173.21.031.41.025.40.930.10.938.41.6
Men180345.81.450.41.366.91.236.51.422.91.531.31.445.81.8
Women165861.21.563.11.579.51.226.11.128.11.628.61.031.21.6
Men
 20–29 years31725.52.932.32.944.43.126.73.420.62.88.92.121.72.7
 30–39 years29140.33.746.63.660.63.332.82.723.03.617.42.536.52.9
 40–49 years31153.92.958.32.976.52.942.53.428.22.922.52.643.23.9
 50–59 years23651.93.555.33.773.43.441.93.219.51.942.54.358.53.0
 60–69 years28560.14.363.34.281.23.545.93.027.01.960.03.970.13.5
 ≥70 years36351.63.153.03.173.92.432.92.918.32.264.62.965.22.4
 White97648.61.548.61.567.11.437.61.624.22.031.51.644.72.1
 African American34536.52.936.52.957.83.021.92.512.61.737.82.641.32.3
 Mexican American36438.03.878.12.978.12.944.32.926.53.224.92.450.13.3
Women
 20–29 years24544.33.348.53.463.03.213.72.331.83.42.00.810.51.9
 30–39 years27056.14.658.34.677.02.920.12.827.63.44.11.016.42.4
 40–49 years30661.92.963.12.981.92.323.72.331.33.024.52.429.93.3
 50–59 years23768.03.769.73.584.92.832.14.227.93.743.33.842.43.6
 60–69 years29076.73.177.63.087.52.543.23.924.33.056.04.051.63.7
 ≥70 years31072.13.272.53.290.32.336.73.921.62.474.22.957.32.8
 White85958.62.258.62.277.21.626.81.527.72.026.21.228.71.9
 African American35276.72.176.72.188.01.914.61.627.22.747.22.537.72.5
 Mexican American31675.53.292.51.992.51.934.52.139.03.427.42.541.93.5

Participants with metabolic syndrome were characterized by numerous changes in anthropometric, physiological, and biochemical parameters (Table 5). Only the estimated GFR and concentrations of LDL-C, potassium, and cotinine did not differ between participants with and without metabolic syndrome.

Table 5.   Age-adjusted means of anthropometric, physiological, and biochemical parameters among US adults aged ≥20 years, according to metabolic syndrome status, National Health and Nutrition Examination Survey 2003–2006
 Metabolic syndromeNo metabolic syndromeP value
nMeanSEnMeanSE
  1. *Metabolic syndrome defined using waist circumference criteria of ≥102 cm in men and ≥88 in women.

  2. WC, waist circumference; SBP, DBP, systolic and diastolic blood pressure, respectively; TG, triglyceride; HDL-C, high-density lipoprotein–cholesterol; BMI, body mass index; GFR, glomerular filtration rate; ACR, albumin:creatinine ratio; LDL-C, low-density lipoprotein–cholesterol; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase; GGT, γ-glutamyltransferase; LDH, lactate dehydrogenase.

WC (cm)1311110.10.8215092.00.3<0.001
SBP (mmHg)1285127.10.52141118.60.5<0.001
DBP (mmHg)128573.50.5214168.10.4<0.001
Log TG (mg/dL)13115.20.0321504.60.01<0.001
HDL-C (mg/dL)131145.20.6215059.60.4<0.001
Glucose (mg/dL)1311112.11.1215095.60.6<0.001
HbA1c (%)13095.70.0421435.30.02<0.001
BMI (kg/m2)130933.00.4214626.30.1<0.001
GFR (mL/min per 1.73 m2)130893.70.6214294.70.40.123
Log urinary ACR (mg/g)13072.20.0521321.90.02<0.001
Total cholesterol (mg/dL)1311204.11.72150196.70.9<0.001
LDL-C (mg/dL)1233117.81.52133115.51.00.188
ALT (U/L)129930.70.7213224.20.4<0.001
AST (U/L)129926.80.5213224.80.40.002
ALP (U/L)130871.71.2214266.80.6<0.001
GGT (U/L)130838.24.1214224.70.60.002
LDH (U/L)1298129.11.22132125.80.70.017
Uric acid (mg/dL)13086.00.0521425.20.03<0.001
Potassium (mmol/L)13084.00.0121424.00.010.552
Albumin (g/dL)130841.70.1214242.40.1<0.001
Globulin (g/dL)13073.00.0221412.90.01<0.001
C-Reactive protein (mg/L)13115.90.421493.80.2<0.001
Leukocytes (×109/L)13117.50.121466.60.1<0.001
Log insulin (μU/L)13032.60.0321041.70.02<0.001
Cotinine (ng/mL)131074.96.1214766.64.10.241

The age-adjusted prevalence of metabolic syndrome was lower among participants whose education continued beyond high school compared with those who had not (= 0.013) or had (= 0.003) graduated from high school, was higher among former smokers than current (= 0.027) or never smokers (= 0.063), increased with level of blood pressure (< 0.001), was higher among participants with hypercholesterolemia than those without hypercholesterolemia (< 0.001), increased with BMI (< 0.001), was lower among participants who did ≥150 min/week of leisure time physical activity compared with those who did not (< 0.001), increased with degree of hyperglycemia (< 0.001), increased with CRP concentrations (< 0.001), increased with the degree of microalbuminuria (< 0.001), and was higher among participants with congestive heart failure (= 0.001), coronary heart disease (= 0.001), heart attack (< 0.001), and stroke (= 0.045) than among participants without those conditions (Table 6).

Table 6.   Age-adjusted prevalence of metabolic syndrome by selected factors among adults aged ≥20 years, National Health and Nutrition Examination Survey 2003–2006
 nMetabolic syndrome*Metabolic syndromeMetabolic syndrome
%SE%SE%SE
  1. *Metabolic syndrome was defined using waist circumference (WC) criteria of ≥102 cm in men and ≥88 in women.

  2. Metabolic syndrome was defined using WC criteria of ≥102 cm in men and ≥88 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

  3. Metabolic syndrome was defined using WC criteria of ≥94 cm in men and ≥80 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

Education
 <High school94738.91.841.01.843.81.6
 High school86238.21.739.01.743.31.7
 >High School164931.01.831.31.834.51.7
Smoking status
 Current76732.31.532.81.638.11.6
 Former94738.62.239.42.142.52.6
 Never174533.61.834.51.737.61.5
Blood pressure
 Normal129613.51.414.31.415.91.5
 Prehypertension87431.81.932.51.938.51.7
 Hypertension129165.93.067.13.070.83.0
Total cholesterol (mg/dL)
 <200151529.41.430.01.433.01.3
 ≥200194638.71.839.61.743.11.7
Body mass index (kg/m2)
 <2510658.70.88.90.813.31.0
 25–<30118932.72.134.22.040.12.1
 ≥30120159.81.860.41.860.71.8
Leisure time physical activity (min/week)
 ≥150128827.61.628.11.631.91.6
 <150217338.91.339.81.343.11.2
Glycemic status
 <100 mg/dL193015.41.115.71.118.01.1
 100–125 mg/dL105957.32.459.22.365.62.0
 Undiagnosed diabetes11781.74.583.74.386.24.2
 Previously diagnosed diabetes35278.85.779.05.781.15.7
C-Reactive protein (mg/L)
 <191319.81.520.41.424.01.3
 1–3119433.41.634.51.638.31.6
 >3135346.51.746.91.649.91.5
Glomerular filtration rate (mL/min per 1.73 m2)
 <6032436.97.037.07.040.67.0
 60–89116736.12.437.32.241.32.3
 ≥90195934.81.735.81.739.41.6
Urinary albumin:creatinine ratio (mg/g)
 <30300432.91.333.61.237.01.1
 30–<30036649.73.950.63.853.84.0
 ≥3006955.99.056.09.064.69.3
Congestive heart failure
 Yes10571.59.971.69.972.29.8
 No334233.81.234.51.138.11.1
Coronary heart disease
 Yes15956.46.156.46.158.56.1
 No328933.71.234.41.138.01.1
Angina pectoris
 Yes12640.34.540.34.542.94.3
 No332233.81.134.61.138.11.0
Heart attack
 Yes15753.84.153.84.157.43.6
 No330133.81.134.51.138.01.1
Stroke
 Yes14445.35.645.35.646.15.6
 No331433.61.134.41.137.91.0

Table 7 shows independent associations between several factors not directly related or indirectly related through high correlations (such as BMI and waist circumference) to the five factors used to define metabolic syndrome and prevalent metabolic syndrome. Based on the adjusted Wald F-tests, significant associations were noted for age (positive), gender (men higher than women), race or ethnicity, educational status, hypercholesterolemia (positive), CRP concentrations (positive), leisure time physical activity (inverse), microalbuminuria (positive), and hyperinsulinemia (positive). In a separate model that also included BMI as a continuous variable, most of the previously significant associations remained so, although the adjusted prevalence ratios weakened in some instances. Educational status, smoking status, and microalbuminuria were not significant contributors to the model.

Table 7.   Associations between selected characteristics and metabolic syndrome among 3261 US adults aged ≥20 years, National Health and Nutrition Examination Survey 2003–2006
 Metabolic syndrome*
Model 1Model 2
Adjusted prevalence ratio (95% CI)P adjusted Wald FAdjusted prevalence ratio (95% CI)P adjusted Wald F
  1. Each variable is adjusted for all other variables in table.

  2. *Metabolic syndrome was defined using waist circumference (WC) criteria of ≥102 cm in men and ≥88 in women.

  3. Metabolic syndrome was defined using WC criteria of ≥102 cm in men and ≥88 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

  4. Metabolic syndrome was defined using WC criteria of ≥94 cm in men and ≥80 in women for White, African American, and other participants and ≥90 cm in men and ≥80 cm in women for Mexican American and other Hispanic participants.

Metabolic syndrome*
 Age (years)1.02 (1.01, 1.02)<0.0011.02 (1.02, 1.02)<0.001
 Gender
  Men1.21 (1.10, 1.33)<0.0011.24 (1.11, 1.37)<0.001
  Women1.001.00
 Race or ethnicity
  White1.000.0091.000.001
  African American0.82 (0.72, 0.94)0.77 (0.68, 0.87)
  Mexican American0.89 (0.74, 1.07)0.95 (0.79, 1.15)
  Other0.56 (0.38, 0.82)0.62 (0.41, 0.93)
 Education
  <High school1.000.0461.000.109
  High school1.03 (0.90, 1.17)0.97 (0.86, 1.10)
  >High School0.88 (0.75, 1.04)0.87 (0.75, 1.00)
 Smoking status
  Current0.88 (0.77, 1.00)0.1470.97 (0.85, 1.10)0.851
  Former0.99 (0.88, 1.11)1.01 (0.88, 1.15)
  Never1.001.00
 Total cholesterol (mg/dL)
  ≥2001.36 (1.20, 1.55)<0.0011.31 (1.16, 1.48)<0.001
  <2001.001.00
 C-Reactive protein (mg/L)
  <10.46 (0.39, 0.54)<0.0010.65 (0.55, 0.76)<0.001
  1–30.79 (0.71, 0.87)0.96 (0.86, 1.07)
  >31.001.00
 Leisure time physical activity (min/week)
  ≥1501.000.0011.000.004
  <1501.25 (1.11, 1.40)1.19 (1.06, 1.33)
 Urinary albumin (mg/g)
  <301.000.0191.000.262
  30–<3001.17 (1.02, 1.34)1.09 (0.94, 1.25)
  ≥3001.37 (1.02, 1.83)1.16 (0.82, 1.64)
 Insulin (μU/mL)
  ≥202.07 (1.84, 1.00)<0.0011.36 (1.19, 1.57)<0.001
  <201.001.00
 Body mass index (kg/m2)1.06 (1.05, 1.07)<0.001
Metabolic syndrome
 Age (years)1.02 (1.01, 1.02)<0.0011.02 (1.02, 1.02)<0.001
 Gender
  Men1.24 (1.14, 1.36)<0.0011.27 (1.15, 1.41)<0.001
  Women1.001.00 
 Race or ethnicity
  White1.00<0.0011.00<0.001
  African American0.82 (0.72, 0.94)0.77 (0.68, 0.88)
  Mexican American1.07 (0.91, 1.27)1.15 (0.97, 1.35)
  Other0.73 (0.52, 1.01)0.80 (0.56, 1.13)
 Education
  <High school1.000.0361.000.078
  High school1.03 (0.90, 1.18)0.98 (0.87, 1.10)
  >High school0.88 (0.75, 1.03)0.86 (0.74, 0.99)
 Smoking status
  Current0.87 (0.77, 0.99)0.1150.96 (0.84, 1.09)0.783
  Former0.98 (0.88, 1.10)1.00 (0.87, 1.14)
  Never1.001.00
 Total cholesterol (mg/dL)
  ≥2001.35 (1.19, 1.53)<0.0011.31 (1.16, 1.48)<0.001
  <2001.001.00
 C-Reactive protein (mg/L)
  <10.48 (0.41, 0.55)<0.0010.66 (0.57, 0.77)<0.001
  1–30.80 (0.72, 0.88)0.97 (0.87, 1.09)
  >31.001.00
 Leisure time physical activity (min/week)
  ≥1501.000.0011.000.003
  <1501.25 (1.11, 1.41)1.20 (1.07, 1.34)
 Urinary albumin (mg/g)
  <301.000.0261.000.311
  30–<3001.16 (1.02, 1.32)1.08 (0.94, 1.24)
  ≥3001.34 (1.01, 1.78)1.15 (0.82, 1.60)
 Insulin (μU/mL)
  ≥202.05 (1.82, 2.31)<0.0011.36 (1.19, 1.55)<0.001
  <201.001.00
 Body mass index (kg/m2)1.06 (1.05, 1.07)<0.001
Metabolic syndrome
 Age (years)1.02 (1.01, 1.02)<0.0011.02 (1.02, 1.02)<0.001
 Gender
  Men1.29 (1.17, 1.42)<0.0011.31 (1.19, 1.44)<0.001
  Women1.001.00
 Race or ethnicity
  White1.000.0061.00<0.001
  African American0.87 (0.78, 0.97)0.82 (0.74, 0.92) 
  Mexican American0.99 (0.84, 1.16)1.04 (0.89, 1.22) 
  Other0.67 (0.48, 0.93)0.72 (0.51, 1.01) 
 Education
  <High school1.000.0091.000.045
  High school1.04 (0.93, 1.17)1.00 (0.90, 1.11)
  >High school0.89 (0.76, 1.04)0.87 (0.76, 1.01)
 Smoking status
  Current0.92 (0.81, 1.03)0.3381.00 (0.89, 1.12)0.983
  Former0.98 (0.87, 1.10)0.99 (0.86, 1.13)
  Never1.001.00
 Total cholesterol (mg/dL)
  ≥2001.32 (1.18, 1.48)<0.0011.28 (1.14, 1.43)<0.001
  <2001.001.00
 C-Reactive protein (mg/L)
  <10.51 (0.46, 0.58)<0.0010.68 (0.60, 0.76)<0.001
  1–30.82 (0.75, 0.90)0.97 (0.88, 1.07)
  >31.001.00
 Leisure time physical activity (min/week)
  ≥1501.00<0.0011.000.002
  <1501.23 (1.11, 1.38)1.19 (1.07, 1.32)
 Urinary albumin (mg/g)
  <301.000.0061.000.119
  30–<3001.17 (1.03, 1.33)1.10 (0.97, 1.25)
  ≥3001.37 (1.10, 1.71)1.21 (0.93, 1.58)
 Insulin (μU/mL)
  ≥201.88 (1.67, 2.11)<0.0011.33 (1.16, 1.51)<0.001
  <201.001.00
 Body mass index (kg/m2)1.05 (1.04, 1.06)<0.001

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Our analyses using the newest definition of metabolic syndrome and the most recently available data provide the most current estimates of metabolic syndrome among adults in the US. The prevalence of metabolic syndrome remains high, generally ranging between 34.3% and 38.5% depending on the criteria for abdominal obesity. In 2009, the estimated number of adults aged ≥20 years in the US was approximately 223 million. Thus, the total number of adults in the US who have metabolic syndrome ranges from almost 77 million to almost 86 million. The prevalence of metabolic syndrome from the present study is similar to a recent estimate from the same dataset that used the 2004 National Heart, Lung, and Blood Institute/American Heart Association definition.15 Although the prevalence of metabolic syndrome increased as expected as the thresholds for waist circumference grew smaller, the associations between metabolic syndrome and important correlates were generally similar for the three variations of the definition we used in the present study.

Despite the high prevalence of metabolic syndrome and the intense interest in this syndrome during much of this decade, recognition by the public appears limited. A survey of 211 097 adults found that only 0.6% reported having metabolic syndrome and <15% of adults were cognizant of metabolic syndrome.16 The low percentage of respondents in that survey who reported having ever been told that they had metabolic syndrome calls into question how aggressive health care providers are in diagnosing metabolic syndrome.

The new harmonizing definition of metabolic syndrome attempts to bridge differences between two major competing definitions of this syndrome. For countries using the 102/88 cm thresholds for waist circumference, the harmonizing definition is no different than the AHA/NHLBI 2005 definition and, thus, does not represent an advance in the conceptualization of the syndrome. However, for many countries the new definition will produce different prevalence estimates than estimates based on previous definitions by the IDF or NCEP.

Nevertheless, the reconciliation between two of the major definitions of metabolic syndrome should have several salutary effects. Clinicians will no longer have to choose between competing definitions, and it is possible that removing a potential source of diagnostic uncertainty may stimulate health care providers to be more vigilant in looking for the syndrome. A single definition should also facilitate the job of researchers in conducting their research. The principal source of uncertainty in the definition of the syndrome, at least in the US, lies in the criteria to be used in defining abdominal obesity. The recent scientific statement suggested thresholds of 102 cm for men and 88 cm for women in the US.11 However, the 2005 AHA/NHLBI definition allowed for ethnic-specific thresholds to be used.

Abdominal obesity is the most prevalent component of metabolic syndrome. Even using the most conservative approach to define abdominal obesity, over half the adults in the US have abdominal obesity. Using the IDF criteria, almost three-quarters of adults have abdominal obesity. These stunning estimates underscore the need for effective population strategies to reduce energy intake and increase energy expenditure. Because a large percentage of adults see a physician every year, health care providers are uniquely situated to treat their patients who have metabolic syndrome. The cornerstone of such treatment is therapeutic lifestyle change. Research has demonstrated that therapeutic lifestyle change can be effective in patients with hypertension, hyperlipidemia, and hyperglycemia.17

The associations between metabolic syndrome and demographic, lifestyle, anthropometric, biochemical, and physiological factors that we found in our analyses are consistent with other reports in the literature.18,19 The demographic patterns are generally similar to those described previously among US adults, except that in the present analysis the prevalence of metabolic syndrome among Mexican American men was lower, but not significantly different, than that among White men.20 The associations with the biochemical and physiological variables underscore that numerous abnormalities are present in people with metabolic syndrome. Thus, metabolic syndrome is characterized by inflammation, insulin resistance, and, to the extent that microalbuminuria is associated with endothelial dysfunction, by endothelial dysfunction.

In conclusion, the prevalence of metabolic syndrome using the harmonizing definition of metabolic syndrome is high among adults in the US. When less-restrictive definitions of central obesity are applied, the prevalence increases, but associations with important correlates are minimally affected. Major public health and professional organizations continue to endorse the concept of metabolic syndrome, underscoring its seriousness as a public health and clinical issue.11 To the extent that metabolic syndrome can be viewed as a window on cardiometabolic health, the high prevalence of the syndrome among US adults casts a cloud on the future health of the US population. Increases in the prevalence of diabetes in the US have been documented21 and further increases are likely if the prevalence of obesity and metabolic syndrome should continue to increase. Decreasing the high prevalence of metabolic syndrome in the US necessitates tackling the obesity epidemic, reducing sedentary behavior, and improving levels of physical activity. Like a hand in a glove, both population-based and individual-based strategies can contribute to achieve these aims.

Disclosure

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

The contents of this paper have not been published elsewhere. The authors have no conflicts of interest, financial or otherwise, to report.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References
  • 1
    Ford ES. Risks for all-cause mortality, cardiovascular disease, and diabetes associated with the metabolic syndrome: a summary of the evidence. Diabetes Care. 2005; 28: 176978.
  • 2
    Ford ES, Li C, Sattar N. Metabolic syndrome and incident diabetes: current state of the evidence. Diabetes Care. 2008; 31: 1898904.
  • 3
    Alberti KG, Zimmet PZ. Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: diagnosis and classification of diabetes mellitus provisional report of a WHO consultation. Diabet Med. 1998; 15: 53953.
  • 4
    World Health Organization. Definition, diagnosis, and classification of diabetes mellitus and its complications. Report of a WHO consultation. Part I: diagnosis and clasisfication of diabetes mellitus. World Health Organization, Geneva, 1999.
  • 5
    Balkau B, Charles MA. Comment on the provisional report from the WHO consultation. European Group for the Study of Insulin Resistance (EGIR). Diabet Med. 1999; 16: 4423.
  • 6
    Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the Third Report of The National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III). JAMA. 2001; 285: 248697.
  • 7
    Bloomgarden ZT. Definitions of the insulin resistance syndrome: the 1st World Congress on the Insulin Resistance Syndrome. Diabetes Care. 2004; 27: 82430.
  • 8
    Grundy SM, Brewer HB Jr, Cleeman JI, Smith SC Jr, Lenfant C. Definition of metabolic syndrome: Report of the National Heart, Lung, and Blood Institute/American Heart Association conference on scientific issues related to definition. Circulation. 2004; 109: 4338.
  • 9
    Alberti KG, Zimmet P, Shaw J. The metabolic syndrome: a new worldwide definition. Lancet. 2005; 366: 105962.
  • 10
    Grundy SM, Cleeman JI, Daniels SR et al. Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement. Circulation. 2005; 112: 273552.
  • 11
    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. 2009; 120: 16405.
  • 12
    Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey. 2009. Available from: http://wwwcdcgov/nchs/nhaneshtm, accessed 13 July 2009.
  • 13
    US Department of Health and Human Services. 2008 Physical activity guidelines for Americans. ODPHP Publication No. U0036. 2008. Available from: http://www.health.gov/paguidelines/pdf/paguide.pdf, accessed 20 January 2010.
  • 14
    Levey AS, Stevens LA, Schmid CH et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009; 150: 60412.
  • 15
    Ervin RB. Prevalence of metabolic syndrome among adults 20 years of age and over, by sex, age, race and ethnicity, and body mass index: United States, 2003–2006. Natl Health Stat Report. 2009; (13): 17.
  • 16
    Lewis SJ, Rodbard HW, Fox KM, Grandy S. Self-reported prevalence and awareness of metabolic syndrome: findings from SHIELD. Int J Clin Pract. 2008; 62: 116876.
  • 17
    Gordon NF, Salmon RD, Franklin BA et al. Effectiveness of therapeutic lifestyle changes in patients with hypertension, hyperlipidemia, and/or hyperglycemia. Am J Cardiol. 2004; 94: 155861.
  • 18
    Laaksonen DE, Niskanen L, Lakka HM, Lakka TA, Uusitupa M. Epidemiology and treatment of the metabolic syndrome. Ann Med. 2004; 36: 33246.
  • 19
    Bonora E, Kiechl S, Willeit J et al. Metabolic syndrome: epidemiology and more extensive phenotypic description. Cross-sectional data from the Bruneck Study. Int J Obes Relat Metab Disord. 2003; 27: 12839.
  • 20
    Ford ES, Giles WH, Dietz WH. Prevalence of the metabolic syndrome among US adults: findings from the third National Health and Nutrition Examination Survey. JAMA. 2002; 287: 3569.
  • 21
    Cowie CC, Rust KF, Ford ES et al. Full accounting of diabetes and pre-diabetes in the U.S. population in 1988–1994 and 2005–2006. Diabetes Care. 2009; 32: 28794.