Re: “Effects of a Passive Online Software Application on Heart Rate Variability and Autonomic Nervous System Balance” by Rubik

Dear Editor:

In recent years, technology-based approaches to alternative and complementary medicine have increasingly been explored and endorsed. Appropriately, Rubik conducted the “first clinical trial” evaluating the health benefits of a “purported subtle energy technology” mobile application (Heart+ App). Hypothesized to work by interacting with the “biofield”, Rubik found that the app significantly reduces the low frequency to high frequency ratio (LF/HF) from spectral analysis of heart rate variability compared with placebo. ¹ This finding was interpreted by Rubik to indicate a beneficial effect of the app on autonomic nervous system balance. However, setting aside the contested issue of what LF/HF actually means for autonomic nervous system balance, ² the analysis in Rubik's study contained a statistical error.

Table 4 of Rubik's study reports the results of an independent sample t-test comparing LF/HF after intervention with the Heart+ App versus after intervention with a sham app. However, the degrees of freedom of the t-test was reported as 118, which indicates that each of the 60 Heart+ App observations, and each of the 60 control observations, were treated as independent (i.e., sample size was treated as 60 per intervention). This is incorrect, as measurements were made in triplicate and in reality, there were only 20 independent observations (20 subjects) per intervention. The difference between replicate measurements and independent repeats and the statistical implications of this has been covered in detail by Vaux et al. ³

Hence, using the reported means and variances, as well as the corrected sample size of 20 in each group, an independent t-test of the data demonstrates no significant difference in LR/HR after intervention with the Heart+ App compared with the sham app (mean difference = −1.29, 95% confidence interval = −2.96 to 0.38, p = 0.126). ⁴ Given the error in table 4, we also question whether the paired t-tests reported in table 2 have been performed correctly. It should further be noted that since this is a crossover trial, a paired analysis for table 4 would have been more apt than the independent t-test chosen by Rubik.

Contrary to the conclusions made by Rubik, the reported results fail to prove that the tested “subtle energy technology” affects autonomic nervous system balance.