Sleep Apnea Linked to High Blood Pressure in Lungs of Adults With Scleroderma

Obstructive sleep apnea (OSA) is associated with an increased risk of pulmonary hypertension in people with scleroderma, a study suggests.

The study, “Impact of concomitant obstructive sleep apnea on pulmonary involvement and main pulmonary artery diameter in adults with scleroderma,” was published in the journal Sleep and Breathing.

Up to 90% of people with scleroderma experience some form of lung involvement. For instance, up to 40% of people with scleroderma will develop pulmonary arterial hypertension (PAH), which refers to high blood pressure within the lungs.

OSA occurs when the muscles of the throat relax abnormally during sleep, causing the airways to become blocked. Although the association of OSA with inflammatory disease has been suggested, the link between OSA and scleroderma, with or without pulmonary involvement, is less clear.

“It is also unclear to which extent a concomitant OSA is associated with pulmonary hypertension in scleroderma patients,” the researchers wrote.

To address this, they conducted a clinical trial (NCT02740569) reporting data for 62 people with scleroderma (58 women, mean age 48 years) who underwent sleep assessments as well as tests of lung function. Forty-three participants had limited scleroderma, and 19 had diffuse scleroderma.

The gold standard for detecting PAH is right heart catheterization, where a thin tube is inserted into the blood vessels near the heart. However, since this method is invasive, the researchers used high-resolution computed tomography (HRCT) imaging to measure main pulmonary artery diameter (mPAD) — the width of the primary artery connecting the heart with the lungs. An enlarged mPAD, defined as a minimum of 27 millimeter (mm) in women and at least 29 mm in men, is thought to be predictive of PAH.

Lung involvement, more generally, was also derived from HRCT data by calculating the Warrick score, which rates the severity of abnormalities. A Warrik score of 7 or greater was defined as pulmonary involvement.

Individuals with diffuse scleroderma were more likely than those with limited scleroderma to have lung involvement, as indicated by both a higher mean Warrick score (17.1 vs. 10) and a greater percentage of individuals with a Warrick score of 7 or above (84.2% vs. 55.8%).

In the overall group, 20 participants (32.3%) had OSA, 17 of whom had limited scleroderma and three had diffuse disease. Patients with OSA were significantly older (mean age 55.14 vs. 45.3) and had a higher rate of obesity (55% vs. 23.8%) and hypertension (35% vs. 9.5%).

The rate of lung involvement did not significantly differ based on OSA status: about two-thirds of participants with OSA had lung involvement, and a similar rate was found for patients who did not have OSA. Also, no significant differences were seen in average scores of lung function tests, such as forced vital capacity.

A significantly higher rate of enlarged mPAD was found among individuals with OSA (50%) than without (14.3%). In addition, participants with OSA had a higher mean mPAD (27.8 mm) than those without OSA (24.2 mm).

Additional analyses showed that having OSA correlated with a 4.7 times greater risk for enlarged mPAD, after accounting for factors such as age and body mass index.

“We conclude that OSA was associated with risk for pulmonary hypertension independent of pulmonary involvement in this cohort,” the researchers wrote.

However, the limited number of participants and the fact this was a single-center study warrant further research to validate the results, they added.

Also, the data do not suggest that OSA causes high lung blood pressure, but rather that the two are associated. As such, it is impossible to predict if treating OSA would have benefits for pulmonary hypertension based on the current results.

“Whether or not the treatment of concomitant OSA in patients with scleroderma reduces this risk [of pulmonary hypertension] needs to be further evaluated,” the scientists wrote.