Normative references of heart rate variability and salivary alpha-amylase in a healthy young male population - PubMed (original) (raw)

Normative references of heart rate variability and salivary alpha-amylase in a healthy young male population

Hiromitsu Kobayashi et al. J Physiol Anthropol. 2012.

Abstract

Background: This study aimed to present normative reference values of heart rate variability and salivary alpha-amylase in a healthy young male population with a particular focus on their distribution and reproducibility.

Methods: The short-term heart rate variability of 417 young healthy Japanese men was studied. Furthermore, salivary alpha-amylase was measured in 430 men. The average age of the subjects were 21.9 years with standard deviation of 1.6 years. Interindividual variations in heart rate variability indices and salivary alpha-amylase levels were plotted as histograms. Data are presented as the mean, median, standard deviation, coefficient of variation, skewness, kurtosis, and fifth and 95th percentiles of each physiological index.

Results: Mean recorded values were heart period 945.85 ms, log-transformed high frequency component 9.84 ln-ms2, log-transformed low frequency component 10.42 ln-ms2, log-transformed low frequency to high frequency ratio 0.58 ln-ratio, standard deviation of beat-to-beat interval 27.17 ms and root mean square of successive difference 37.49 ms. The mean value of raw salivary alpha-amylase was 17.48 U/mL, square root salivary alpha-amylase 3.96 sqrt[U/mL] and log-transformed salivary alpha-amylase 2.65 ln[U/mL]. Log-transformed heart rate variability indices exhibited almost symmetrical distributions; however, time-domain indices of heart rate variability (standard deviation of beat-to-beat interval and root mean square of successive difference) exhibited right-skewed (positive skewness) distributions. A considerable right-skewed distribution was observed for raw salivary alpha-amylase. Logarithmic transformation improved the distribution of salivary alpha-amylase, although square root transformation was insufficient. The day-to-day reproducibility of these indices was assessed using intraclass correlation coefficients. Intraclass correlation coefficients of most heart rate variability and salivary indices were approximately 0.5 to 0.6. Intraclass correlation coefficients of raw salivary markers were approximately 0.6, which was similar to those of heart rate variability; however, log transformation of the salivary markers did not considerably improve their reproducibility. Correlations between sympathetic indicators of heart rate variability and salivary alpha-amylase were not observed.

Conclusion: Because the sample population examined in this study involved limited age and gender variations, the present results were independent of these factors and were indicative of pure interindividual variation.

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Figures

Figure 1

Figure 1

Histograms of the interindividual variation of heart period, log-transformed heart rate variability indices and time-domain heart rate variability indices. HRV indices included lnHF, lnLF and ln(LF/HF). Right-skewed distributions were observed for lnHF and the time-domain indices (SDNN and rMSSD).

Figure 2

Figure 2

Histograms of the interindividual variation of salivary alpha-amylase. From left to right, the distributions of raw, square root-, and natural logarithmic-transformed sAA values are presented. The histogram of raw amylase exhibited a markedly skewed distribution. Numerical transformations (square root and natural logarithm) improved skewness, although square root transformation appeared insufficient.

Figure 3

Figure 3

Correlation between sympathetic indicators of heart rate variability and salivary alpha-amylase. The left panel shows the correlation of log-transformed sAA to lnLF of HRV. The right panel shows the correlation of log-transformed sAA to ln(LF/HF) of HRV. There were no significant correlations between sAA and the sympathetic indicators of HRV.

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