To test at the population level whether people with multiple metabolic syndrome (MMS) disorders have reduced cardiac autonomic activity (CAA).
We examined the association between the level of CAA and MMS disorders, at the degree of clustering and the segregate combination levels, using a random sample of 2,359 men and women aged 45–64 years from the biracial, population-based Atherosclerosis Risk in Communities (AR1C) Study. Supine resting 2-min beat-to-beat heart rate data were collected. High-frequency (HF) (0.15–0.35 Hz) and low-frequency (LF) (0.025–0.15 Hz) spectral powers, the ratio of LF to HF, and the SD of all normal R-R intervals (SDNN) were used as the conventional indices of heart rate variability (HRV) to measure CAA. The MMS disorders included hypertension, type 2 diabetes, and dyslipidemia.
HRV indices were significantly lower in individuals with MMS disorders. The multivariable adjusted mean HF was 0.85 (beat/min)2 in subjects with all three MMS disorders, in contrast to 1.31 beat/min)2 in subjects without any MMS disorder. At the segregated combination level, the multivariable adjusted means ± SEM of HF were 1.34 ± 0.05, 1.16 ± 0.05, 1.01 ± 0.17, and 1.34 ± 0.05 (beat/min)2, respectively, for subjects without any MMS disorder, with hypertension only, with diabetes only, and with dyslipidemia only, and the means ± SEM of HF were 0.93 ± 0.04,0.70 ± 0.15, and 1.20 ± 0.05 eat/min)2, respectively, for subjects with diabetes and hypertension, diabetes and dyslipidemia, and hypertension and dyslipidemia. An increase in fasting insulin of 1 SD was associated with 88% higher odds of having a lower HF The pattern of associations was similar for LF and SDNN.
These findings suggest that MMS disorders adversely affect cardiac autonomic control and a reduced cardiac autonomic control may contribute to the increased risk of subsequent cardiovascular events in individuals who exhibit MMS disorders.