Heart rate variability in individuals with Down syndrome – A systematic review and meta-analysis

Introduction: Down syndrome (DS) results in many changes, including dysfunction in cardiac autonomic modulation. Heart rate variability (HRV) analysis evaluates the autonomic function and it is a predictor of adverse cardiovascular events. Objective: To present results of a systematic review and a meta-analysis about heart rate variability in individuals with DS. Method: A systematic review was performed on PubMed, PubMed Central and Web of science databases. We included articles that exhibited all the terms: “Down Syndrome” “heart rate variability” “autonomic nervous system” “autonomic dysfunction” and “cardiac autonomic modulation”. We conducted the meta-analysis to compare “DS” to “controls” during rest. Random effects models were used, as were appropriate tests for heterogeneity. Results: From 271 studies, 13 were included in our review. These are conducted with volunteers from a wide age range, of either gender, and not taking medications. Meta-analysis displayed that there were no significant differences between the groups at rest, except the RMSSD, which revealed a significant (Z = −2.80, p = 0.005) main effect (Hedge's g = −0.55, 95% CI [−0.93; −0.16]), indicating difference in individuals with DS compared with controls. Conclusion: There is autonomic dysfunction in individuals with DS, which may or may not be expressed at rest, but it is usually demonstrated in an autonomic task. Meta-analysis specified that there was no significant alteration between DS and the controls during rest, except RMSSD index which was lower in DS than controls. PROSPERO: CRD42017068647.