OBJECTIVE

To compare the prevalence in metabolic syndrome (MetSyn) between 1988–1994 and 1999–2006 among U.S. adults of different races or ethnicities.

RESEARCH DESIGN AND METHODS

Analysis of data on 6,423 adult men and nonpregnant women aged ≥20 years from Third National Health and Nutrition Examination Survey (NHANES III) and 6,962 participants from the combined NHANES 1999–2006 were done. The revised National Cholesterol Education Program Adult Treatment Panel III definition was used to calculate MetSyn.

RESULTS

Both the unadjusted prevalence (27.9 ± 1.1% to 34.1 ± 0.8%, P < 0.001) and age-adjusted prevalence (29.2 ± 1.0% to 34.2 ± 0.7%, P < 0.001) increased from NHANES III to NHANES 1999–2006, respectively. Although MetSyn prevalence was highest in Mexican Americans, significant increases in prevalence occurred among non-Hispanic whites and non-Hispanic blacks, especially among younger women.

CONCLUSIONS

The persistent increase of MetSyn among U.S. adults is a serious public health concern because it raises the likelihood of increased prevalence of type 2 diabetes.

The metabolic syndrome (MetSyn) is a constellation of metabolic abnormalities and is associated with increased risk of developing diabetes (1), cardiovascular disease (2), and higher mortality from all causes (3). Among the few studies using nationally representative samples on MetSyn (4,,,,9), Ford et al. (9) estimated an increasing trend of MetSyn prevalence by comparing the Third National Health and Nutrition Examination Survey (NHANES III) and NHANES 1999–2000 data. However, because of the smaller sample size of NHANES 1999–2000, the change in MetSyn prevalence for various subpopulations, which is necessary to track age and ethnicity specific trends, was not estimated. Therefore, the objective of this study is to compare the prevalence of MetSyn between NHANES III and NHANES 1999–2006 among U.S. adults of different races or ethnicities.

We identified the cases of MetSyn using the revised American Heart Association/National Cholesterol Education Program Adult Treatment Panel III definition (10), including medication uses for appropriate MetSyn criteria. Data for this study were obtained from public-use datasets of the NHANES III, NHANES 1988–1994 (data release 11#1A), and four continuous NHANES data releases: 1999–2000, 2001–2002, 2003–2004, and 2005–2006. Details of survey and laboratory procedure of NHANES are published elsewhere (11,13). Data from NHANES 1999–2006 were combined for this study to produce estimates of MetSyn for demographic subpopulations (e.g., sex-age-race/ethnicity) with greater statistical reliability. Because the data on fasting triglycerides and fasting glucose were required to identify MetSyn and those measurements were done on a subsample population, the sample weights for the subsample were used in this study.

The appropriate sample weights for combined NHANES 1999–2006 were constructed using National Center for Health Statistics guidelines (14). To maintain the consistency of blood pressure data between the two surveys, the procedure described by Ford et al. (9) was followed.

The continuous NHANES measured fasting glucose and serum triglycerides from blood samples drawn in the morning; therefore, only participants who attended a morning examination session for NHANES III were included in this analysis. Otherwise, the sample includes men and nonpregnant women aged ≥20 years who fasted for at least 8 h. The number of participants in the final analysis was 6,423 for NHANES III and 6,962 for NHANES 1999–2006. Statistical analyses to calculate prevalence were performed using the survey procedures in SAS software version 9.1 (SAS Institute, Cary, NC). The statistical significance of the change in MetSyn prevalence between the two surveys was examined by Student t test, in which the square root of the sum of the squared standard errors was utilized to calculate the pooled standard error of the difference in the mean.

The age-adjusted prevalence of four of the five metabolic abnormalities of MetSyn increased significantly between the surveys for women: abdominal obesity 46.0 ± 1.4% to 58.0 ± 1.1%, P < 0.001; hypertriglyceridemia 24.7 ± 1.2% to 27.6 ± 0.8%, P = 0.042; high blood pressure (HBP) 27.8 ± 0.9% to 36.6 ± 0.8%, P < 0.001; high fasting glucose 24.2 ± 1.2% to 29.2 ± 1.0%, P = 0.002. However, for men, age-adjusted prevalence significantly increased in abdominal obesity (30.4 ± 1.6% to 41.1 ± 1.1%, P < 0.001) and HBP (32.0 ± 0.8% to 40.0 ± 0.7%, P < 0.001) only. The age-adjusted prevalence of low HDL cholesterol significantly decreased in both sexes (men: 36.4 ± 1.7% to 27.6 ± 1.0%, P < 0.001; women: 39.6 ± 1.4% to 33.8 ± 1.1%, P = 0.001) between the surveys.

Both age-adjusted and age-specific prevalence of MetSyn for NHANES 1999–2006 were significantly higher than for NHANES III (Table 1). The unadjusted (P = 0.012) and age-adjusted (P = 0.046) prevalence increased significantly between the two surveys for men; however, there was no significant change in any of the three age-groups. For women, both unadjusted and age-adjusted (P < 0.001) prevalence increased significantly between the two surveys, with a significant increase noted in all three age-groups. Among non-Hispanic White (NHW) subjects, both men and women showed significant increases in unadjusted (men: P = 0.010; women: P = 0.001) and age-adjusted (men: P = 0.048; women: P = 0.007) prevalence of MetSyn. However, when classified by age-groups, only women aged 20–39 years showed significant increase (P = 0.010). Prevalence of MetSyn did not change significantly among non-Hispanic Black (NHB) men (P > 0.050) between the two surveys, but NHB women aged 20–39 years showed a significant increase in prevalence (P = 0.036). The age-adjusted prevalence of MetSyn in NHANES 1999–2006 was highest among Mexican Americans (men: 36.6 ± 1.9%; women: 42.6 ± 1.7%) with little change in this group from NHANES III. Using the unadjusted prevalence rates from combined sample population of NHANES 1999–2006, we estimated that about 32.4 million men and 35.3 million women in U.S. had MetSyn. Among U.S. adults with MetSyn, ∼50.6 million were NHW, ∼6.3 million were NHB, and ∼4.6 million were Mexican Americans.

Table 1

Age-specific (unadjusted) and age-adjusted (adjusted) prevalence of the metabolic syndrome among U.S. adults aged ≥20 years in the NHANES III and NHANES 1999–2006

NHANES III
NHANES 1999–2006
Absolute change %Relative change %P
n%(SEM)n%(SEM)
Total          
        Unadjusted 6,423 27.9 (1.1) 6,962 34.1 (0.8) 6.3 22.6 <0.001 
        Adjusted 6,423 29.2 (1.0) 6,962 34.2 (0.7) 5.0 17.0 <0.001 
    Men          
        Unadjusted 3,059 29.3 (1.6) 3,582 34.2 (1.1) 4.9 16.8 0.012 
        Adjusted 3,059 31.4 (1.4) 3,582 34.9 (1.0) 3.5 11.2 0.046 
        Aged 20–39 years 1,217 15.7 (2.1) 1,229 20.2 (1.4) 4.4 28.1 0.080 
        Aged 40–59 years 839 36.3 (2.3) 1,114 41.2 (1.7) 5.0 13.7 0.083 
        Aged 60+ years 1,003 50.3 (2.3) 1,239 49.9 (2.0) −0.4 −0.8 0.899 
    Women          
        Unadjusted 3,364 26.5 (1.4) 3,380 34.1 (1.10) 7.5 28.4 <0.001 
        Adjusted 3,364 27.1 (1.2) 3,380 33.3 (1.0) 6.2 22.8 <0.001 
        Aged 20–39 years 1,447 10.7 (1.7) 1,061 16.7 (1.2) 6.0 55.5 0.003 
        Aged 40–59 years 943 30.2 (2.3) 1,113 36.3 (1.7) 6.2 20.4 0.033 
        Aged 60+ years 974 50.2 (2.2) 1,206 56.8 (1.9) 6.6 13.1 0.022 
NHW          
    Men          
        Unadjusted 1,284 30.8 (2.0) 1,881 37.0 (1.3) 6.3 20.3 0.010 
        Adjusted 1,284 32.1 (1.9) 1,881 36.5 (1.2) 4.4 13.8 0.048 
        Aged 20–39 years 337 16.6 (2.8) 523 22.3 (2.0) 5.8 35.0 0.090 
        Aged 40–59 years 361 37.1 (3.0) 618 42.2 (2.0) 5.1 13.7 0.164 
        Aged 60+ years 586 50.4 (2.5) 740 51.4 (2.4) 1.0 2.1 0.762 
    Women          
        Unadjusted 1,462 26.5 (1.6) 1,725 33.3 (1.4) 6.8 25.6 0.001 
        Adjusted 1,462 26.2 (1.4) 1,725 31.4 (1.3) 5.2 20.0 0.007 
        Aged 20–39 years 446 9.1 (1.9) 483 16.0 (1.8) 6.8 74.5 0.010 
        Aged 40–59 years 411 29.4 (2.7) 543 33.0 (2.2) 3.7 12.6 0.292 
        Aged 60+ years 605 50.2 (2.5) 699 55.2 (2.1) 5.0 9.9 0.121 
NHB          
    Men          
        Unadjusted 762 20.2 (1.2) 634 22.0 (1.6) 1.8 8.8 0.372 
        Adjusted 762 23.1 (1.4) 634 24.9 (1.6) 1.9 8.0 0.388 
        Aged 20–39 years 375 13.9 (1.5) 261 11.9 (2.0) −2.0 −14.1 0.439 
        Aged 40–59 years 210 24.3 (3.10) 192 26.6 (3.2) 2.3 9.3 0.613 
        Aged 60+ years 177 36.9 (3.3) 181 44.6 (3.3) 7.7 21.0 0.098 
    Women          
        Unadjusted 913 26.4 (1.7) 656 34.3 (1.7) 7.9 30.0 0.001 
        Adjusted 913 30.6 (1.7) 656 36.5 (1.6) 5.9 19.3 0.014 
        Aged 20–39 years 472 12.6 (1.6) 244 18.9 (2.5) 6.3 49.8 0.036 
        Aged 40–59 years 268 35.6 (2.7) 230 40.7 (3.4) 5.1 14.2 0.241 
        Aged 60+ years 173 53.3 (4.0) 182 59.9 (2.7) 6.6 12.3 0.180 
Mexican American          
    Men          
        Unadjusted 893 28.5 (2.2) 810 29.4 (2.2) 0.9 3.3 0.767 
        Adjusted 893 37.8 (2.1) 810 36.6 (1.9) −1.2 −3.1 0.671 
        Aged 20–39 years 457 17.6 (2.7) 324 18.9 (2.8) 1.3 7.3 0.743 
        Aged 40–59 years 226 48.0 (3.5) 228 44.4 (3.0) −3.6 −7.5 0.433 
        Aged 60+ years 210 56.1 (5.4) 258 54.5 (3.6) −1.6 −2.8 0.810 
    Women          
        Unadjusted 853 33.1 (1.6) 741 36.4 (2.2) 3.3 10.0 0.222 
        Adjusted 853 41.7 (1.7) 741 42.6 (1.7) 0.9 2.2 0.701 
        Aged 20–39 years 475 19.8 (1.9) 241 20.9 (2.9) 1.1 5.3 0.758 
        Aged 40–59 years 217 51.4 (3.2) 244 49.6 (3.3) −1.8 −3.5 0.699 
        Aged 60+ years 161 63.6 (3.8) 256 68.6 (3.9) 5.1 8.0 0.352 
Other          
    Men          
        Unadjusted 120 25.8 (4.7) 257 28.9 (3.3) 3.1 12.0 0.590 
        Adjusted 120 30.5 (4.3) 257 31.9 (3.2) 1.4 4.5 0.798 
        Aged 20–39 years 48 9.1 (5.3) 121 17.5 (3.2) 8.4 92.8 0.177 
        Aged 40–59 years 42 33.5 (0.8) 76 46.5 (7.1) 13.0 38.9 0.316 
        Aged 60+ years 30 62.3 (0.5) 60 33.0 (4.8) −29.3 −47.1 0.012 
    Women          
        Unadjusted 136 22.7 (4.6) 258 37.9 (4.2) 15.2 67.1 0.015 
        Adjusted 136 24.0 (3.9) 258 39.3 (3.8) 15.3 63.6 0.005 
        Aged 20–39 years 54 15.6 (7.5) 93 14.8 (4.6) −0.8 −4.9 0.931 
        Aged 40–59 years 47 21.7 (8.3) 96 48.8 (4.6) 27.1 124.4 0.005 
        Aged 60+ years 35 42.2 (7.7) 69 66.1 (6.8) 23.9 56.6 0.021 
NHANES III
NHANES 1999–2006
Absolute change %Relative change %P
n%(SEM)n%(SEM)
Total          
        Unadjusted 6,423 27.9 (1.1) 6,962 34.1 (0.8) 6.3 22.6 <0.001 
        Adjusted 6,423 29.2 (1.0) 6,962 34.2 (0.7) 5.0 17.0 <0.001 
    Men          
        Unadjusted 3,059 29.3 (1.6) 3,582 34.2 (1.1) 4.9 16.8 0.012 
        Adjusted 3,059 31.4 (1.4) 3,582 34.9 (1.0) 3.5 11.2 0.046 
        Aged 20–39 years 1,217 15.7 (2.1) 1,229 20.2 (1.4) 4.4 28.1 0.080 
        Aged 40–59 years 839 36.3 (2.3) 1,114 41.2 (1.7) 5.0 13.7 0.083 
        Aged 60+ years 1,003 50.3 (2.3) 1,239 49.9 (2.0) −0.4 −0.8 0.899 
    Women          
        Unadjusted 3,364 26.5 (1.4) 3,380 34.1 (1.10) 7.5 28.4 <0.001 
        Adjusted 3,364 27.1 (1.2) 3,380 33.3 (1.0) 6.2 22.8 <0.001 
        Aged 20–39 years 1,447 10.7 (1.7) 1,061 16.7 (1.2) 6.0 55.5 0.003 
        Aged 40–59 years 943 30.2 (2.3) 1,113 36.3 (1.7) 6.2 20.4 0.033 
        Aged 60+ years 974 50.2 (2.2) 1,206 56.8 (1.9) 6.6 13.1 0.022 
NHW          
    Men          
        Unadjusted 1,284 30.8 (2.0) 1,881 37.0 (1.3) 6.3 20.3 0.010 
        Adjusted 1,284 32.1 (1.9) 1,881 36.5 (1.2) 4.4 13.8 0.048 
        Aged 20–39 years 337 16.6 (2.8) 523 22.3 (2.0) 5.8 35.0 0.090 
        Aged 40–59 years 361 37.1 (3.0) 618 42.2 (2.0) 5.1 13.7 0.164 
        Aged 60+ years 586 50.4 (2.5) 740 51.4 (2.4) 1.0 2.1 0.762 
    Women          
        Unadjusted 1,462 26.5 (1.6) 1,725 33.3 (1.4) 6.8 25.6 0.001 
        Adjusted 1,462 26.2 (1.4) 1,725 31.4 (1.3) 5.2 20.0 0.007 
        Aged 20–39 years 446 9.1 (1.9) 483 16.0 (1.8) 6.8 74.5 0.010 
        Aged 40–59 years 411 29.4 (2.7) 543 33.0 (2.2) 3.7 12.6 0.292 
        Aged 60+ years 605 50.2 (2.5) 699 55.2 (2.1) 5.0 9.9 0.121 
NHB          
    Men          
        Unadjusted 762 20.2 (1.2) 634 22.0 (1.6) 1.8 8.8 0.372 
        Adjusted 762 23.1 (1.4) 634 24.9 (1.6) 1.9 8.0 0.388 
        Aged 20–39 years 375 13.9 (1.5) 261 11.9 (2.0) −2.0 −14.1 0.439 
        Aged 40–59 years 210 24.3 (3.10) 192 26.6 (3.2) 2.3 9.3 0.613 
        Aged 60+ years 177 36.9 (3.3) 181 44.6 (3.3) 7.7 21.0 0.098 
    Women          
        Unadjusted 913 26.4 (1.7) 656 34.3 (1.7) 7.9 30.0 0.001 
        Adjusted 913 30.6 (1.7) 656 36.5 (1.6) 5.9 19.3 0.014 
        Aged 20–39 years 472 12.6 (1.6) 244 18.9 (2.5) 6.3 49.8 0.036 
        Aged 40–59 years 268 35.6 (2.7) 230 40.7 (3.4) 5.1 14.2 0.241 
        Aged 60+ years 173 53.3 (4.0) 182 59.9 (2.7) 6.6 12.3 0.180 
Mexican American          
    Men          
        Unadjusted 893 28.5 (2.2) 810 29.4 (2.2) 0.9 3.3 0.767 
        Adjusted 893 37.8 (2.1) 810 36.6 (1.9) −1.2 −3.1 0.671 
        Aged 20–39 years 457 17.6 (2.7) 324 18.9 (2.8) 1.3 7.3 0.743 
        Aged 40–59 years 226 48.0 (3.5) 228 44.4 (3.0) −3.6 −7.5 0.433 
        Aged 60+ years 210 56.1 (5.4) 258 54.5 (3.6) −1.6 −2.8 0.810 
    Women          
        Unadjusted 853 33.1 (1.6) 741 36.4 (2.2) 3.3 10.0 0.222 
        Adjusted 853 41.7 (1.7) 741 42.6 (1.7) 0.9 2.2 0.701 
        Aged 20–39 years 475 19.8 (1.9) 241 20.9 (2.9) 1.1 5.3 0.758 
        Aged 40–59 years 217 51.4 (3.2) 244 49.6 (3.3) −1.8 −3.5 0.699 
        Aged 60+ years 161 63.6 (3.8) 256 68.6 (3.9) 5.1 8.0 0.352 
Other          
    Men          
        Unadjusted 120 25.8 (4.7) 257 28.9 (3.3) 3.1 12.0 0.590 
        Adjusted 120 30.5 (4.3) 257 31.9 (3.2) 1.4 4.5 0.798 
        Aged 20–39 years 48 9.1 (5.3) 121 17.5 (3.2) 8.4 92.8 0.177 
        Aged 40–59 years 42 33.5 (0.8) 76 46.5 (7.1) 13.0 38.9 0.316 
        Aged 60+ years 30 62.3 (0.5) 60 33.0 (4.8) −29.3 −47.1 0.012 
    Women          
        Unadjusted 136 22.7 (4.6) 258 37.9 (4.2) 15.2 67.1 0.015 
        Adjusted 136 24.0 (3.9) 258 39.3 (3.8) 15.3 63.6 0.005 
        Aged 20–39 years 54 15.6 (7.5) 93 14.8 (4.6) −0.8 −4.9 0.931 
        Aged 40–59 years 47 21.7 (8.3) 96 48.8 (4.6) 27.1 124.4 0.005 
        Aged 60+ years 35 42.2 (7.7) 69 66.1 (6.8) 23.9 56.6 0.021 

The age-adjusted prevalence of U.S. adults reporting diabetes (other than pregnancy related) or having a fasting blood glucose ≥126 mg/dl significantly increased in both sexes (men: 8.1 ± 0.6% to 10.5 ± 0.6%, P = 0.005; women: 5.8 ± 0.6% to 8.5 ± 0.5%, P = 0.001) between the two surveys. The age-adjusted prevalence of MetSyn among U.S. men without diabetes did not change significantly (27.6 ± 1.4% to 30.6 ± 1.1%, P = 0.08); however, the prevalence significantly increased for women without diabetes (24.0 ± 1.2% to 29.4 ± 1.0%, P = 0.001), including women aged 20–39 years (10.0 ± 1.6% to 15.8 ± 1.2%, P = 0.003) and aged 40–59 years (25.8 ± 2.4% to 31.6 ± 1.7%, P = 0.049).

Ford et al. (9) estimated that ∼50 million U.S. adults in 1990 and ∼64 million in 2000 had MetSyn, representing a 28% increase in prevalence. From the combined NHANES 1999–2006 data, we estimated ∼68 million U.S. adults had MetSyn, or a further increase of 6%. The prevalence of MetSyn in U.S. adults in 1999–2006 was 34.1 ± 0.8% (after age adjustment 34.2 ± 0.7%), which is a significant increase from 1988–1994, and more so in women (28.4%) than in men (16.8%). Further, in both NHW and NHB the prevalence of MetSyn significantly increased in women, particularly younger women (aged 20–39 years). The increased prevalence of MetSyn was primarily due to increases in abdominal obesity and HBP.

An increase in MetSyn prevalence is expected to be followed by an increase in diabetes prevalence, though of a lesser magnitude. Between the two surveys, there was a 4.3% increase in age-adjusted prevalence of MetSyn among adults without diabetes and a 2.6% increase in diabetes. As we continue to see an increase in MetSyn, especially in certain ethnic groups and younger women, we will see a concomitant increase in diabetes and its comorbidities and associated medical costs.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

No potential conflicts of interest relevant to this article were reported.

A.M. and G.L. contributed equally to study design, data analysis, and manuscript writing.

We thank Paul S. Fisk, MS, North Dakota State University, for his assistance with data analysis. We also thank Subrata K. Roy, PhD, Indian Statistical Institute, Kolkata, India, for his help during the review process.

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