Key result
Metabolic syndrome was associated with a significant decrease in all short-term heart rate variability variables (P<0.001) after eliminating the influence of daytime physical activity.
Why the study?
Conflicting data exist on HRV in MetS subjects due to the confounding influence of physical activity when comparing resting HRV to 24 h Holter monitoring.
Does the elimination of physical activity influence using an ARX model reveal differences in 24 h heart rate variability between subjects with and without metabolic syndrome?
Observational (n=106)
Does the elimination of physical activity influence using an ARX model reveal differences in 24 h heart rate variability between subjects with and without metabolic syndrome?
p-value: p=<0.001
Eliminating the confounding effect of physical activity during 24-hour Holter monitoring reveals that metabolic syndrome is associated with significantly blunted short-term heart rate variability, reflecting reduced parasympathetic tone.
Should not yet change autonomic assessment in practice; leaves open prognostic value of activity-adjusted HRV in metabolic syndrome.
Background and Objectives: The available research shows conflicting data on the heart rate variability (HRV) in metabolic syndrome (MetS) subjects. The discrepancy suggests a methodical shortcoming: due to the influence of physical activity, the standard measuring of HRV at rest is not comparable with HRV assessment based on 24 h Holter monitoring, which is preferred because of its comprehensiveness. To obtain a more reliable measure and to clarify to what extent HRV is altered in MetS, we assessed a 24 h HRV before and after the elimination of the influence of physical activity. Materials and Methods: We investigated 69 metabolic syndrome (MetS) and 37 control subjects, aged 50–55. In all subjects, 24 h monitoring of electrocardiogram, blood pressure, and actigraphy profiles were conducted. To eliminate the influence of day-time physical activity on RR intervals (RRI), a linear polynomial autoregressive model with exogenous terms (ARX) was used. Standard spectral RRI analysis was performed. Results: Subjects with MetS had blunted HRV; the diurnal SDNN index was reliably lower in the MetS group than in control subjects. The elimination of the influence of physical activity did not reveal a significant HRV change in long-term indices (SDNN, SDANN, and SD2), whilst adjacent RRI values (RMSSD, pNN50, and SD1) and SDNN index significantly increased (p < 0.001). An increase in the latter indices highlighted the HRV difference between the MetS and control groups; a significant (p < 0.001) decrease of all short-term HRV variables was found in the MetS group (p < 0.01), and low-frequency spectral components were less pronounced in the MetS group. Conclusion: The application of a polynomial autoregressive model in 24 h HRV assessment allowed for the exclusion of the influence of physical activity and revealed that MetS is associated with blunted HRV, which reflects mitigated parasympathetic tone.
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Slušnienė et al. (2019) conducted an observational in Metabolic syndrome (n=106). Metabolic syndrome vs. Control subjects without metabolic syndrome was evaluated on Short-term heart rate variability variables (p=<0.001). Metabolic syndrome was associated with a significant decrease in all short-term heart rate variability variables (P<0.001) after eliminating the influence of daytime physical activity.
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