Cheap blood test ‘can predict your risk of terrifying condition that can kill you in your sleep’

A SIMPLE blood test could help predict your risk of obstructive sleep apnoea (OSA), scientists hope.

Around 1.5million adults in the UK have the condition, which causes loud snoring and can stop you breathing while you sleep.

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Many sufferers wake up choking or gasping for breath, while others feel extremely tired during the day.

In rare cases, it can be fatal, SleepApnea.org warns.

If left untreated, sufferers have a 30 per cent greater risk of heart disease and are 60 per cent more likely to have a stroke, studies show.

The most common risk factors for developing OSA include age, obesity, smoking, alcohol and type 2 diabetes.

Scientists in São Paulo, Brazil, looked at whether a blood test could also be used to predict the likelihood of someone developing it.

The “simple, low-cost” health check measures the level of homocysteine, an amino acid, in the blood.

There is strong evidence that abnormally high levels of homocysteine, known as hyperhomocysteinemia, can cause alterations in blood vessel walls and increase a person’s risk of heart disease, thrombosis, heart attacks and strokes.

The team from the Federal University of São Paulo studied data from 854 volunteers aged 20 to 80, who, in 2007, took a polysomnography test to measure their apnoea-hypopnea index (AHI), which counts the number of times breathing slows or stops during an average hour of sleep.

“Up to five events per hour is considered normal. Between five and 15 is classed as mild apnoea, 15 to 30 is moderate, and more than 30 is severe,” first author Vanessa Cavalcante-Silva said.

More than half of participants (54.4 per cent) were diagnosed with no apnoea, while 24.4 per cent had mild, 12.4 per cent had moderate, and 8.8 per cent had severe apnoea.

The same group were also classified according to the level of homocysteine in their blood.

Up to 10 µmol/l was considered normal, 10 to 15 µmol/l moderate, and more than 15 µmol/l high.

“When we cross-tabulated the data, we saw that subjects with high levels of homocysteine also had a higher AHI,” Cavalcante-Silva said.

“Those with more than 15 µmol/l had an AHI that was 7.43 higher on average than those with less than 10 µmol/l.”

This was the case even when accounting for weight, biological sex and age, Cavalcante-Silva added.

In the second stage, the researchers analysed data for the same volunteers in 2015.

As some people dropped out, the proportions changed. Almost a third (29.8 per cent) had no apnoea, 31.2 per cent had mild, 19.4 per cent had moderate, and 19.6 per cent had it severely.

“In this stage, the aim was to find out whether homocysteine was a risk factor for the development of apnoea, so we excluded participants who had apnoea in 2007 and analysed the data for those who were then sleeping normally,” Cavalcante-Silva said.

“In this subgroup, a rise of 1 µmol/l in the 2007 level of homocysteine represented a rise of 0.98 per cent in the risk of a diagnosis of apnoea in 2015.”

‘SIMPLE AND LOW-COST’

Professor Monica Levy Andersen added: “It’s a low risk, but it exists.

“The fact is that we presented a novel factor which is easy to measure and has clinical and practical applicability.

“Now, it would be interesting to conduct a study with a different format, in which the participants are assessed annually and we could obtain more extensive data.”

The authors noted that currently, they have only identified a link between the two.

Prof Andersen said: “We don’t yet know whether apnoea causes the rise in blood levels of homocysteine or the rise in levels of this amino acid causes severe apnoea.

“Our hypothesis is that it’s a two-way correlation.

“It would be a good idea for more physicians in all specialties to include a homocysteine test in the blood work prescribed for checkups of people over 40.

“It’s simple and low-cost, and the results could provide more information on this correlation, at the very least.”

The study is published in the European Archives of Oto-Rhino-Laryngology.