A comparison of different definitions of metabolic syndrome for the risks of atherosclerosis and diabetes

Database from 1999 to 2015 from a Health Examination Program at one’s own expense at the Health Care Center of Taoyuan Chang Gung Memorial Hospital was gathered in the cross-sectional population-based study. In our recent report, the database and the selection criteria have been described previously to test the weight of different WC cut-off values of the MetS diagnosis for the risks of atherosclerosis and diabetes in a Chinese population [16]. Briefly, every subject was demanded to be asymptomatic for infection and to complete a uniform protocol, containing well-designed questionnaires revealing their family and personal lifestyle patterns and medical histories, as well as measurements of body weight, height, BP, WC, and brachial-ankle PWV/ankle-brachial index (baPWV/ABI), applied to estimate the severity of arterial stiffness. The inclusion guide was obtainable information of fasting plasma glucose, and 171,839 subjects in all were sifted. The exclusion guides were less than 20 years old, an ABI value less than 0.9, or any missing information of the other 4 MetS components, post-prandial plasma glucose or baPWV (Fig. 1). The included subjects were diagnosed as the MetS or not on the basis of the ATP III/AHA/NHLBI and IDF criteria.

All subjects were required to give their written informed consent. The Ethics Committee of the Institutional Review Board of Chang Gung Memorial Hospital (Approval Number: 102-4175B) approved the study, and we did on basis of the ethical principles of the Declaration of Helsinki.

A baPWV more than or equal to 1400 cm/s was set as a higher level indicating more serious arterial stiffness [17]. A high fasting plasma glucose level more than or equal to 6.99 mmol/L or postprandial plasma glucose level more than or equal to 11.10 mmol/L was set as diabetic-level hyperglycemia indicating an increased risk of diabetes [18].

On the basis of the 2005 ATP III/AHA/NHLBI [10] and 2005 IDF [11] criteria, the MetS diagnosis and scores were concluded. The former contains: (1) raised WC (≥ 102 cm for men or ≥ 88 cm for women); (2) elevated BP (≥ 130/85 mmHg); (3) raised fasting plasma glucose level (≥ 5.55 mmol/L); (4) decreased plasma high-density lipoprotein cholesterol level (HDL-C) (< 1.0 mmol/L for men or < 1.3 mmol/L for women); and (5) raised plasma triglyceride level (≥ 1.7 mmol/L). Any 3 of the above 5 components established the ATP III/AHA/NHLBI-MetS diagnosis. All components in the IDF definition were the same as in the ATP III/AHA/NHLBI except for the WC cutoff value (≥ 90 cm for men or ≥ 80 cm for women, considering abdominal obesity as its core component). Abdominal obesity plus any 2 of the other 4 components established the IDF-MetS diagnosis. Each component contributed one point to the ATP III/AHA/NHLBI- and IDF-MetS scores for each subject. For the IDF-MetS score, all subjects who did not meet the WC cutoff value were given a score of 0.

Brachial BP measured by an appropriately sized cuff was recorded in duplicate, and values were reported as a mean of two recordings. WC was measured at the midpoint between the iliac crest and lowest rib when a subject was in a standing position with feet 15 cm apart. All subjects underwent laboratory measurements, and after fasting overnight for 12 h, venous serum samples were gathered to test in the early morning. The biochemical measurements contained tests of fasting plasma glucose, HDL-C, and triglyceride at the only laboratory of our hospital. We supplied the uniform food and drink for every subject, and tested their post-prandial plasma glucose after 2 h.

An automated machine (Colin VP-1000, Omron, Japan) were applied to achieve measurements of baPWV. Details were recorded in our previous report [19]. Briefly, all subjects were demanded not to consume any stimulant something, including cigarette, coffee or alcoholic drinks overnight. The special examination room was kept at a control atmospheric temperature. The technicians operating at our single center were well-disciplined and familiar with their work. Both baPWVs were computed as the distance/duration between both ankles and the right arm, and their average was represented as the last reported baPWV [16, 19, 20].

We applied SPSS version 22.0 for Windows 7 (SPSS Inc., Chicago, USA) to analyze most data which were presented as the average (± SD) or frequency in last. A p value less than 0.05 was applied to determine statistical significance. We applied the Kolmogorov–Smirnov test to assess all variables for normal distribution. Moreover, the comparisons were performed using one-way analysis of variance for continuous variables and using 2-sample proportions test for the prevalence of the both MetS. We plotted receiver operator characteristic (ROC) curves for the ATP III/AHA/NHLBI- and IDF-MetS scores to correlate with a higher baPWV and diabetic-level hyperglycemia. Next we compared the areas under the ROC curves (AUC–ROC) for the performance by applying R software version 3.3.2 (R Foundation, Austria). The optimal cutoff points of both MetS scores were obtained by computing the equation: sensitivity − (1 − specificity), when the maximum values were reached, called the Youden index [21].

In all, 26,735 adult subjects were concluded from 2006 to 2015 with an average age of 55 (± 12) years (range 20–101 years), WC of 87 (± 12) cm, SBP of 135 (± 20) mmHg, DBP of 81 (± 12) mmHg, fasting glucose level of 5.55 (± 1.55) mmol/L, post-prandial glucose level of 6.44 (± 3.00) mmol/L, HDL-C level of 1.32 (± 0.36) mmol/L, triglyceride level of 1.57 (± 1.13) mmol/L, and baPWV of 1506 (± 336) cm/s. Among them, 10,514 (39.3%) were female and 2738 (10.2%) suffered from diabetic-level hyperglycemia.

After adjusting for sex and age, a stepwise raise in the baPWV corresponded to the ATP III/AHA/NHLBI-MetS score (p for trend < 0.001) (Fig. 2a). In addition, except for a score of 0 indicating no abdominal obesity, a stepwise raise in baPWV also corresponded to the IDF-MetS score after adjusting for sex and age (p for trend < 0.001) (Fig. 2b).

After adjusting for sex and age, a stepwise raise in the prevalence of diabetic-level hyperglycemia corresponded to the ATP III/AHA/NHLBI-MetS score (p for trend < 0.001) (Fig. 2c). In addition, except for a score of 0 indicating no abdominal obesity, a stepwise raise in the prevalence of diabetic-level hyperglycemia also corresponded to the IDF-MetS score after adjusting for sex and age (p for trend < 0.001) (Fig. 2d).

The AUC-ROC for the performance of the ATP III/AHA/NHLBI-MetS score to correlate with a higher baPWV was 0.685 compared to 0.595 for the IDF-MetS score (Fig. 3a). The AUC of the former was significantly higher than that of the latter (p < 0.001) (Table 1). There was no effect of gender because of the gender-specific WC cutoff values in both MetS criteria.

The AUC-ROC for the performance of the ATP III/AHA/NHLBI-MetS score to correlate with diabetic-level hyperglycemia was 0.791 compared to 0.665 for the IDF-MetS score (Fig. 3b). The AUC of the former was significantly higher than that of the latter (p < 0.001) (Table 1). There was no effect of gender because of the gender-specific WC cutoff values in both MetS criteria.

The optimal cutoff point of the ATP III/AHA/NHLBI-MetS score to correlate with a higher baPWV was more than or equal to two, with a better sensitivity from 32.7 to 62.2% (Table 2). Likewise, that of the IDF-MetS score was more than or equal to two, with a better sensitivity from 35.0 to 49.2%.

The optimal cutoff point of the ATP III/AHA/NHLBI-MetS score to correlate with diabetic-level hyperglycemia was more than or equal to two, with a better sensitivity from 62.6 to 89.4% (Table 2). Differently from the form, the optimal cutoff point of the IDF-MetS score was more than or equal to three, which was equivalent to the current definitions with a sensitivity of 57.3%.