Results
At baseline, of the 4,905 subjects, 45.3% were men with a median age of 40.0 years (41.2 ± 11.0), while 54.7% were women with a median age of 42 years (41.7 ± 10.2). The follow-up interval was 4.78 ± 0.41 years for men and 4.81 ± 0.39 years for women, respectively. The baseline characteristics are summarised in Table 1.
The components of MetS in the population at baseline and follow-up were grouped by HDL level at baseline (Table 2, Table 3, Table 4 and Table 5). Subjects were divided into two age groups (20 to 44 (young) and 45 to 65 (old)). The incidence of MetS at follow-up was analysed by gender and HDL level at baseline (Figures 1 and 2). Young men with high-normal and normal HDL levels had a higher incidence of MetS compared with women in the same groups (2.57% versus 0.77%, and 5.95% versus 3.45%, respectively). The numbers of young men and young women were almost the same in the low HDL group (11.93% versus 10.17%). Whereas the numbers of old men and old women were almost the same in the high-normal, normal, and low HDL groups (4.55% versus 2.56%, 7.77% versus 6.05%, and 9.52% versus 8.00%, respectively).
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Figure 1.
The accumulated incidence of MetS in subjects aged 20–44, stratified by gender and high-density lipoprotein level. *Compared with high-normal HDL group of same gender using χ test, P < 0.025. Compared with male counterpart using χ test, P < 0.05.
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Figure 2.
The accumulated incidence of MetS in subjects aged 45–65, stratified by gender and high-density lipoprotein level. *Compared with high-normal HDL group of same gender using χ test, P < 0.025.
The five most common transitions in each sub-group were identified (Figure 3). As the sample size was too small after grouping by age, the association rule was applied without sub-stratification of age. The support rate of transitions (defined as the percentage changing from initial status to another status via all possible transitions) was examined in the period 2007/2008 to 2011/2012 in the different sub-groups at baseline. For visual simplicity, the five most commonly observed transitions are shown in the relevant parts of Figure 3. The most common transition in both genders with normal-high and normal HDL was "healthy" to "healthy", whereas for the low HDL group, the main transition was from "low HDL" to "healthy". The rates of transition are shown for each gender and HDL group. The confidence rate represents how many cases transitioned within a certain status. For example, 470 males were initially healthy at baseline, and 280 (60.74%) of these stayed healthy, while 54 (11.71%) transitioned to hypertension at the end of the observation period.
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Figure 3.
The support and confidence rate of the top five transitions in all subjects from 2007/2008 to 2011/2012 stratified by sex and high-density lipoprotein groups. (A) in high-normal HDL group of males; (B) in normal HDL group of males; (C) in low HDL group of males; (D) in high-normal HDL group of females; (E) in normal HDL group of females; (F) in low HDL group of females. Abbreviations: H, health, with the absence of any MetS components; BP, high blood pressure; TG, raised triglycerides level; GLU, high fasting plasma glucose; HDL, increased high-density lipoprotein level.