It began from a simple and unexplained physical sensation - a change in the pattern of my heartbeat. Having suffered two years of regular sleep disturbance born of the perils of fatherhood, I began to document the specific biological changes that occurred as my body learnt to anticipate the regularity of interruption.

 

In those frequent moments of somnolent restlessness - tired beyond belief yet unable to capitalise upon any brief moments of respite - I began to notice my heartbeat change pace, and took to measuring it.  Further research uncovered that, when we rest, the heart rate changes to reflect different periods in our natural sleep cycle, and any persistent periods of sleeplessness interferes with this process.