From Wheeze to Clot

Asthma might increase risk for blood clots

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) People with asthma know that they need to be on alert for asthma attacks to make sure they get the treatment they need. A recent study showed that they may also need to look out for signs of blood clots.

Researchers wanted to find out if people with asthma had a higher chance of getting blood clots in their lungs than people without asthma.

They studied the medical records of 648 asthma patients in the Netherlands to look at how many had experienced blood clots.

People with severe asthma had a nine times higher risk for developing blood clots than people without asthma. Mild to moderate asthma patients had a 3.5 times increased risk.

Though the risk for blood clots increases with asthma, it is important to note that blood clots are still a relatively rare event.

"See your doctor if you have trouble breathing."

Christof J. Majoor, MD, of the Department of Respiratory Medicine at the Academic Medical Centre in Amsterdam, The Netherlands, and colleagues wanted to find out whether people with moderate or severe asthma had an increased risk of developing deep vein thrombosis or pulmonary embolisms.

Pulmonary embolism is a condition in which a main artery in the lung becomes blocked. These blockages are usually caused by deep vein thrombosis (DVT).

DVT is a type of blood clot which sits in the veins in the leg. When the clot breaks off and travels to the lung, it is a pulmonary embolus.

For their study, the researchers recruited 648 patients between December 1, 2010 and May 1, 2011 from asthma clinics in the Netherlands. The participants were between the ages of 18 and 88 years old.

Of the total, 365 patients had mild to moderate asthma while 283 patients had severe asthma.  

The participants were given questionnaires that asked about their history with blood clots, if they had taken any blood thinning medications and whether or not they had been taking asthma medication when they had blood clots.  

One of the types of asthma medications they asked about were oral corticosteroids. This is a type of pill that helps reduce inflammation.

If a patient reported that they had had blood clots, the researchers verified the clots in that patient's medical records.

The results showed that people with severe asthma had an almost nine times higher risk of blood clots in their lungs compared to the general population.

They also showed that people with mild to moderate asthma were 3.5 times more likely to have a blood clot in their lungs compared to people without asthma.

While this comparative risk is high, it's important to note that the actual risk for a person with severe asthma is still quite low.

Approximately one person per thousand with severe asthma will develop a blood clot, according to the study results.

Using oral corticosteroids to treat asthma, in addition to having severe asthma, was shown to be a potential risk factor for increased chances of pulmonary embolism.

People that used oral corticosteroids had a 2.82 times higher risk of developing blood clots in their lungs than people who didn't use this medication.

"This is the first time a link has been found between asthma and pulmonary embolism and we believe these results have important clinical implications,” said Dr. Majoor.

“Our findings suggest that people with severe asthma have an increased risk of pulmonary embolism and doctors should increase their awareness of the possibility of this occurrence in order to help prevent this serious event,” he said.

The study was published December 20, 2012 in the European Respiratory Journal.

The research was funded by the Dutch Asthma Foundation. The authors report no potential conflicts of interest.

Reviewed by: 
Review Date: 
February 26, 2013
Last Updated:
March 3, 2013