A new method for analysis of heart rate variability: counting statistics of 1/f fluctuations.

1/f fluctuations in heart rate are usually measured spectral analysis using Fast Fourier Transform. Here, we introduce a new method based on counting the number of QRS complexes in time intervals delta t of various length. For a 1/fb spectrum the variance of counts in delta t follows a power-law as delta t1+b. This method is applied to analyze long term fluctuations in heart rate variability in 10 healthy men. The results show periods of 1/f fluctuations with interpolated periods of white noise during night hours.