Table 1 summarizes the demographic data of 5,854 participants. There were 2,154 (36.80%) participants with Mets and 3,700 (63.20%) participants without Mets. Of the 2,154 participants with Mets, 1,556 (72.24%) had hypertriglyceridemia, 565 (26.63%) had low HDL-C, 1,686 (78.27%) had high blood pressure or were diagnosed with hypertension, and 1,848 (85.79%) had high FPG or were diagnosed with hyperglycemia. The mean age ± standard deviation of the people with Mets was 43.98 ± 13.58. The current study showed that older married men with smoking and alcohol abuse habits were more likely to have Mets than those without these habits (P < 0.05). The participants who were better educated had a lower prevalence of Mets (P < 0.05).
Comparisons of MMSE scores between individuals with Mets and its four components are illustrated in Fig. 1. The mean ± standard deviation of MMSE scores (28.35 ± 2.10) was significantly higher in participants with Mets than in those without Mets (28.93 ± 1.57). People with normal TGs, HDL-C, blood pressure and FPG had higher MMSE scores than those with abnormal TGs, HDL-C, blood pressure, and FPG; all differences were statistically significant (P < 0.05). (The concepts of normal and abnormal are consistent with the diagnostic criteria of Mets.)
We further investigated the risk of cognitive impairment and Mets in different age groups (60 years). Participants with Mets had 2.41-fold odds of having cognitive impairment in the crude model (OR 2.41, 95% CI: 2.01–2.88, P < 0.001), and the association was consistent when controlling for gender, current smoking, and current alcohol consumption (OR 1.51, 95% CI: 1.24–1.83, P < 0.001). After the stratified analysis, the association between Mets and cognitive impairment remained significant. In the group aged < 60 years, the unadjusted and adjusted odds ratios (ORs) and 95% CIs were 1.812 (1.39, 2.36) and 1.374 (1.04, 1.82), respectively. In the other group (age ≥ 60 years), the unadjusted and adjusted ORs and 95% CIs were 1.45 (1.10, 1.91) and 1.40 (1.05, 1.86), respectively.
Table 3 provides information on Mets, each of the 5 Mets components and the odds of cognitive impairment. Abdominal obesity, elevated TGs, elevated blood pressure, and elevated blood glucose were found to be significantly associated with cognitive impairment in Model 1 (all P < 0.001; Table 3), but this association was not seen for low HDL-C.
In Model 2, abdominal obesity had an OR of 1.48 (95% CI: 1.20–1.83, P < 0.001), elevated blood pressure had an OR of 1.46 (95% CI: 1.19–1.78, P < 0.001), and elevated blood glucose had an OR of 1.32 (95% CI: 1.06–1.66, P = 0.014). However, elevated TGs and reduced HDL-C were not associated with cognitive impairment (all P > 0.05, Table 3).
In Model 3, abdominal obesity and elevated blood pressure both had statistically significant results (OR 1.36, 95% CI: 1.09–1.70, P = 0.007; OR 1.32, 95% CI 1.07–1.63, P = 0.010). However, elevated TGs, reduced HDL-C and elevated blood glucose were not significantly associated with cognitive impairment (all P > 0.05, Table 3).
The number of Mets components was related to cognitive impairment. Compared to the reference group with 0 components, the adjusted ORs and 95% CI for subjects in the groups with 3 and 4/5 Mets components were 1.86 (1.22–2.83) and 1.76 (1.15–2.67), respectively. However, similar results were not found in the group with 1 and 2 Mets components (P > 0.05; Table 4).