FEB 99] UNIVERSITY OF WARWICK PRESS RELEASE
Researchers Get To The Heart Of Sleep Disorders
Using sophisticated analysis of heart rate information, researchers at the
University of Warwick have devised a way to diagnose sleep disorders that replaces the
detailed and expensive medical investigations currently used.
The number of patients coming forward with sleeping
disorders is increasing. Birmingham Heartlands Hospital alone dealt with over 400 sleep
disorder cases in the last year. The main problem is sleep apnoea which means stopping
breathing during sleep. This can occur up to 300 times in one night. Consequences of
sleep apnoea include extreme daytime sleepiness, which can result in loss of jobs and even
cause road traffic accidents. People who have sleep apnoea are more likely to suffer high
blood pressure and die from heart attacks. Most sleep disorder patients can only be
diagnosed after a complicated procedure known as polysomnography, for which patients are
admitted to hospital overnight. Whilst asleep, they are tested by an array of instruments
measuring individual leg and eye movements, electrocardiograms (ECGs), brain waves, chest
movements, oxygen level in the blood, snoring and air flow through the nose and mouth.
Every time a sleep apnoea sufferer stops breathing and
subsequently awakes, the heart rate is affected. However, doctors have not so far used
this heart rate effect as a diagnostic tool for two reasons. Firstly, healthy hearts do
not have an entirely regular heart rate, preventing detailed analysis until now. Secondly,
the wide variation across patients in the intensity of sleep apnoea means that it is
impossible to decide on a simple single quantitative measure to look for when examining
ECGs of heart activity. Now researchers at the University of Warwick, working in a cross
departmental research group applying mathematical techniques to medical problems, have
devised a single analysis of the heart rate which will greatly reduce the time - consuming
and expensive polysomnography procedure.
The researchers have combined their knowledge to use
mathematical tools to cope with the heart's irregular rate and the wide variation in the
effects of sleep apnoea on the heart rate.
They experimented with the application of two mathematical
concepts - the Non-equispaced Fourier Transform, and the Discrete Harmonic Wavelet
Transform - to the ECGs of 20 sleep apnoea patients and 20 normal subjects. They
discovered that by using these tools they could indeed simply diagnose sleep apnoea from
the ECG alone. The advantages of this new technique include:-
- The ECG data can be analysed in just 20 minutes.
Polysomnography data takes 4 - 6 hours.
- A patient can take a portable ECG monitor home. They do not
need to be admitted to hospital.
- The technique will allow non - sleep specialist doctors
looking at ECGs of patients to diagnose sleep apnoea, even if they were using the ECG to
look at other conditions.
The team are now looking at the effect of other conditions
on heart rate and believe they can refine the process for application to other heart
conditions, asthma and diabetes.
Mike Hilton, Mathematics in Medicine Initiative Fellow,
University of Warwick Tel: 01203 522844
Dr Mike Chappell, School of Engineering
01203 524309 email: firstname.lastname@example.org
Prof Keith Godfrey, School of Engineering
01203 523144 email: email@example.com
Dr Ron Bates, Dept of Statistics
01203 522062 email: R.A.Bates@warwick.ac.uk
Peter Dunn, University Press Officer