Examples of the power spectral density (PSD) of a 24 h R-R interval series in a double logarithmic plot (decadic logarithm as indicated by ‘log₁₀’).

<p>The slope β denotes the slope of the linear regression calculated using the averaged PSD (grey circles; frequency range: 10⁻⁴ to 10⁻² Hz). Top: male subject, age 7.9 years; bottom: male subject, age 18.1 years.</p

Comparison of different age groups with respect to time and frequency domain measures.

<p>R-R – mean R-R interval, SDNN – standard deviation of R-R interval series, HF – high frequency component, LF – low frequency component, VLF – very low frequency component, ULF – ultra low frequency component, ln ms² – natural logarithm of the absolute values in ms², ln LF/HF - natural logarithm of the ratio LF/HF. Each group shows three values: 24 h averages are plotted in black, night-time (left of black dot) and wake time averages (right of black dot) are plotted in grey. Note that ULF can only be calculated for the entire recording. The frequency domain measures were transformed by taking the natural logarithm to yield normal distributions (indicated by ‘ln ms²’). The symbol above a value/dot refers to comparisons within the same time period (24 h, night-time or wake time).* Group differed from 3 other groups. + Group differed from group <7 years and group 7 to 9 years. □ Group differed from group 7 to 9 years. ▵ Group differed from group 7 to 9 years and group 10 to 13 years.</p

Course of the frequency domain measures during childhood and adolescence.

<p>HF – high frequency component, LF – low frequency component, VLF – very low frequency component, ULF – ultra low frequency component, ln ms² – natural logarithm of the absolute values in ms², ln LF/HF - natural logarithm of the ratio LF/HF. The circles represent 24 h averages. Solid and dashed lines show moving average and the fitted polynomial model of order 3, respectively.</p

Comparison of different age groups with respect to scaling and complexity measures.

<p>Slope β – long-term fractal scaling properties, DFA α₂ – intermediate-term fractal scaling properties, DFA α₁ – short-term fractal scaling properties, ApEn - complexity. Each group shows three values: 24 h averages are plotted in black, night-time (left of black dot) and wake time averages (right of black dot) are plotted in grey. Note that the slope β can only be calculated for the entire recording. The symbol above a value/dot refers to comparisons within the same time period (24 h, night-time or wake time). * Group differed from 3 other groups. + Group differed from group <7 years and group 7 to 9 years. □ Group differed from group 7 to 9 years. ▵ Group differed from group 7 to 9 years and group 10 to 13 years.</p

Course of the mean R-R interval and its accompanying standard deviation (SDNN) as basic time domain measures during childhood and adolescence.

<p>The circles represent 24 h averages. Solid and dashed lines show moving average and the fitted polynomial model of order 3, respectively.</p

Course of the fractal and complexity measures during childhood and adolescence.

<p>Slope β – long-term fractal scaling properties, DFA α₂ – intermediate-term fractal scaling properties, DFA α₁ – short-term fractal scaling properties, ApEn - complexity. The dots represent 24 hour averages. Solid and dashed lines show moving average and the fitted polynomial model of order 3, respectively.</p