Sensitivity to mental effort and test–retest reliability of heart rate variability measures in healthy seniors

ObjectivesTo determine (1) whether heart rate variability (HRV) was a sensitive and reliable measure in mental effort tasks carried out by healthy seniors and (2) whether non-linear approaches to HRV analysis, in addition to traditional time and frequency domain approaches were useful to study such effects.MethodsForty healthy seniors performed two visual working memory tasks requiring different levels of mental effort, while ECG was recorded. They underwent the same tasks and recordings 2 weeks later. Traditional and 13 non-linear indices of HRV including Poincaré, entropy and detrended fluctuation analysis (DFA) were determined.ResultsTime domain, especially mean R-R interval (RRI), frequency domain and, among non-linear parameters – Poincaré and DFA were the most reliable indices. Mean RRI, time domain and Poincaré were also the most sensitive to different mental effort task loads and had the largest effect size.ConclusionsOverall, linear measures were the most sensitive and reliable indices to mental effort. In non-linear measures, Poincaré was the most reliable and sensitive, suggesting possible usefulness as an independent marker in cognitive function tasks in healthy seniors.SignificanceA large number of HRV parameters was both reliable as well as sensitive indices of mental effort, although the simple linear methods were the most sensitive.

► A wide variety of heart rate variability measures have been used to quantify mental effort. ► In this study, mental effort in older adults was associated with changes in heart rate variability. ► In general measures with higher test–retest reliability had greater sensitivity to mental effort. ► Time domain measures were more sensitive to mental effort than frequency domain measures. ► Among non-linear measures, Poincaré was the most sensitive to mental effort.