Subjects
The average frequency of fish intake was 2.32 ± 1.31 days per week. Figure 2 shows the weekly frequencies of fish intake. The subject characteristics and laboratory profiles according to the MHR tertiles are shown in Table 1.
Comparison of the MHR and Lifestyle Behaviors According to the Weekly Frequency of Fish Intake
The subjects' MHR values were compared according to the weekly frequency of fish intake as categorical variables (0–1 day, 2–3 days, 4–5 days, or 6–7 days per week). The MHR was decreased significantly as the weekly frequency of fish intake was increased (Figure 3-1).
As the weekly frequency of fish intake was increased, the proportion of subjects with habitual cigarette smoking was decreased significantly and the proportion of those with an aerobic exercise habit was increased significantly. The weekly frequency of alcohol intake was also increased significantly with an increased weekly frequency of fish intake (Figure 3-2) (Figures with p-values are included).
Comparison of the Subject Characteristics with Cardiometabolic Risk According to the MHR
The body mass index, waist circumference, and proportion of subjects with metabolic syndrome was increased significantly as the MHR tertile was increased. The blood HbA1c levels were also increased significantly as the MHR tertile was increased. The serum LDL-C, TG, and non-HDL-C levels were increased significantly as the MHR tertile was increased. The serum HDL-C level was decreased significantly as the MHR tertile was increased. As the MHR tertile was increased, the proportions of subjects receiving treatment for hypertension and diabetes mellitus were increased significantly, while the proportions of those receiving treatment for hyperuricemia remained unchanged. Thus, these findings suggest that a higher MHR was associated with a worse cardiometabolic risk (Table 1). As the MHR tertile was increased, the WBC count, neutrophil count, monocyte count, and CRP level were increased significantly, while the blood lymphocyte count showed no significant change. The weekly frequency of fish intake was decreased significantly as the MHR tertile was increased. As the MHR tertile was increased, the proportion of subjects with the cigarette smoking habit was also increased significantly, while that of subjects with an aerobic exercise habit and alcohol intake habit was decreased significantly (Table 1 with p-values included).
Multiple Stepwise Regression Analysis to Identify Factors Influencing the MHR, Monocyte Count, and Serum HDL-C level
As shown in Table 2, in model 1, the multiple stepwise regression analysis identified the weekly frequency of fish intake as a negative independent determinant of the MHR. Age, waist circumference, and history of treatment for diabetes mellitus were significant positive independent determinants of the MHR. On the other hand, cigarette smoking habit, aerobic exercise habit, and alcohol intake habit were also significant independent determinants of the MHR.
However, as shown in Figure 3-2, there was a significant correlation between the frequency of fish intake and lifestyle behaviors (cigarette smoking habit, aerobic exercise habit, and alcohol intake habit); therefore, they could confound the association between the frequency of fish intake and the MHR ratio. A two-way ANOVA revealed the absence of an interaction between the weekly frequency of fish intake and the above-mentioned lifestyle behaviors in regard to the relationship with the MHR ratio (p-value for interaction = 0.332, 0.072, and 0.185). These analyses indicated that lifestyle behaviors, as well as a higher frequency of fish intake, were independent determinants of the MHR. This result verified the primary hypothesis of this study.
In model 2, the weekly frequency of fish intake was identified as a negative independent determinant of the MHR. Age, waist circumference, cigarette smoking habit, and history of treatment for diabetes mellitus were found to be significant positive independent determinants of the blood monocyte count. In model 3, the weekly frequency of fish intake was identified as an independent positive determinant of the serum HDL-C level. Waist circumference and cigarette smoking habit were negative independent determinants of the serum HDL-C level. Both aerobic exercise habit and alcohol intake habit were independent positive determinants of the serum HDL-C level (Table 2 with β-coefficient and p-values included).
These results suggest that a high frequency of fish intake may be an independent predictor of a lower blood monocyte count and higher serum HDL-C, and therefore, a lower MHR. Figure 4 shows the relationship between fish intake frequency and monocyte count, serum HDL-C level, and MHR derived from these analyses.
A Risk Stratification for ASCVD by Combining the Serum HDL-C Level with the MHR and Fish Intake Frequency
Figure 5 shows the relationship between the MHR and serum HDL-C levels (left). The vertical axis represents the MHR; the higher the MHR was, the worse the cardiometabolic risk became, as shown in Table 1, and the lower the MHR was, the lower the cardiometabolic risk became. Individual cases with the same serum HDL-C levels had different MHR values (right), and thus the risk of ASCVD could not be precisely determined from the absolute serum HDL-C level alone. The functions of HDL may be approximately deduced from this model. Figure 5 shows that there are different HMRs depending on the number of monocytes in cases with the same serum HDL-C level. Therefore, the HMR provides a risk stratification for ASCVD based on serum HDL-C levels.