Heart rate variability in relation to cognition and behavior in neurodegenerative diseases: A systematic review and meta-analysis

Fig. 1. PRISMA flow diagram.

Fig. 2. Forest plot showing Pearson correlation coefficients between vagally-mediated HRV and cognition/behavior measures reported by all included studies (N = 18). ‘Total’ denotes the sample size, COR and 95% CI denote the Pearson correlation coefficients and associated 95% confidence interval, and Weight is the adjusted random-effects weight using the Sidik-Jonkman estimator, for each study.

Fig. 3. Forest plot showing Pearson correlation coefficients between task-related HRV reactivity/change and cognition/behavior measures. The participant population in all studies was amnestic MCI. Correlations were between HF-HRV rate of change (quadratic term) and processing speed, attention and working memory (Lin_2017 (Lin et al., 2017a)), reduced mental fatigability (Lin_2016 (Lin et al., 2016)) reduced perceived chronic stress severity (McDermott_2019 (McDermott et al., 2019)), between HF-HRV reactivity (HRV task minus HRV rest) and executive function (Lin_2017ii (Lin et al., 2017b), and between change in HR-HRV task (controlled for HRV rest) and processing speed and attention (Lin_2020 (Lin et al., 2020)). As McDermott_2019 stated that a higher HRV quadratic term (greater rate of change) indexed worse acute stress adaptation, which was in contrast to the other studies, it was conservatively interpreted to be the opposite (i.e. higher quadratic term indicating better adaptation) in this analysis for consistency. ‘Total’ denotes the sample size, COR and 95% CI denote the Pearson correlation coefficients and associated 95% confidence interval, and Weight is the adjusted random-effects…

Fig. 4. Forest plot showing Pearson correlation coefficients between resting vagally-mediated HRV and cognition/behavior measures. Only studies that reported measuring HRV during spontaneous breathing in a sitting or supine position were included. All studies employed ECG apart from Guo et al. (2016) which used pulse oximetry. ‘Total’ denotes the sample size, COR and 95% CI denote the Pearson correlation coefficients and associated 95% confidence interval, and Weight is the adjusted random-effects weight using the Sidik-Jonkman estimator, for each study.

Fig. 5. Forest plot showing Pearson correlation coefficients between vagally-mediated HRV and executive function measures. ‘Total’ denotes the sample size, COR and 95% CI denote the Pearson correlation coefficients and associated 95% confidence interval, and Weight is the adjusted random-effects weight using the Sidik-Jonkman estimator, for each study.

Fig. 6. Funnel plot showing low risk of small sample bias across studies included in the meta-analysis. Plot asymmetry was not detected using Egger’s test (p = 0.627).