Cheap blood test ‘could predict risk of terrible condition that could kill you in your sleep’

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

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

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Many patients wake up choking or short of breath, while others feel extremely tired during the day.

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

If left untreated, patients are 30% more at risk of heart disease and 60% 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 someone’s likelihood of developing it.

The “simple and low-cost” health test 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 changes in the walls of blood vessels and increase the risk of heart disease, thrombosis, heart attacks and strokes.

The team from the Federal University of São Paulo studied data from 854 volunteers aged between 20 and 80 years who, in 2007, underwent a polysomnography exam to measure the apnea-hypopnea index (AHI), which counts the number of times the breathing becomes slower or for an average hour of sleep.

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

More than half of the participants (54.4 percent) were diagnosed without apnea, while 24.4 percent had mild apnea, 12.4 percent had moderate apnea and 8.8 percent had severe apnea.

The same group was also classified according to the level of homocysteine ​​in the blood.

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

“When we crossed the data, we saw that individuals with high homocysteine ​​levels also had higher AHI,” said Cavalcante-Silva.

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

This happened even considering weight, biological sex and age, added Cavalcante-Silva.

In the second stage, the researchers analyzed data from the same volunteers in 2015.

As some people dropped out, the proportions changed. Almost a third (29.8 percent) had no apnea, 31.2 percent had mild apnea, 19.4 percent had moderate apnea and 19.6 percent had severe apnea.

“At this stage, the objective was to find out whether homocysteine ​​was a risk factor for the development of apnea, so we excluded participants who had apnea in 2007 and analyzed the data of those who then slept normally,” said Cavalcante-Silva.

“In this subgroup, a 1 µmol/l increase in homocysteine ​​level in 2007 represented a 0.98 percent increase in the risk of an apnea diagnosis in 2015.”

‘Simple and low cost’

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

“The fact is that we present a new factor, easy to measure and with clinical and practical applicability.

“Now it would be interesting to do a study with a different format, in which participants were evaluated annually and we could obtain more extensive data.”

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

Professor Andersen said: “We do not yet know whether apnea causes increased blood levels of homocysteine ​​or whether increased levels of this amino acid cause severe apnea.

“Our hypothesis is that it is a bidirectional correlation.

“It would be a good idea for more doctors of all specialties to include a homocysteine ​​test in the blood tests prescribed for screening people over the age of 40.

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

The study is published in European Archives of Otorhinolaryngology.