1. A method of analyzing a ballistocardiogram to detect an arrhythmia comprising: selecting a first time window of interest of the ballistocardiogram, said first time window comprising a cardiac component signal incorporating a plurality of heart beats; defining a reference energy content including one of: determining a heart rate from said first time window and calculating the reference energy content by integrating an area under the cardiac component signal of a part of the cardiac component signal incorporating a single heart beat and multiplying the calculated energy content by the determined heart rate and first time window duration, OR defining a further time window of the ballistocardiogram by displacing the first time window by a predefined amount of time and determining the reference energy content by integrating an area under the cardiac component signal over the further time window; calculating an actual energy content including one of: determining a heart rate from said first time window and calculating the actual energy content by integrating an area under the cardiac component signal of a part of the cardiac component signal incorporating a single heart beat and multiplying the calculated energy content by the determined heart rate and first time window duration, OR defining a further time window of the ballistocardiogram by displacing the first time window by a predefined amount of time and determining the actual energy content by integrating an area under the cardiac component signal over the further time window, comparing the calculated actual energy content with the determined reference energy content; and generating an arrhythmia signal when a difference between the actual energy content and the reference energy content exceeds a predefined threshold.