Patients with more severe obstructive sleep apnea, measured by the apnea-hypopnea index, were more likely to have incident venous thromboembolism, researchers reported in Chest.

“We found that VTE was more common in patients with OSA, as we expected. However, much of this risk seems to be driven by obesity, which may be the common risk factor

that predisposes patients to both OSA and VTE,” Michael V. Genuardi, MD, MS, FACC, assistant professor of clinical medicine at the Center for Sleep and Cardiovascular Outcomes Research at the University of Pittsburgh School of Medicine and the division of cardiology at the Perelman School of Medicine at the University of Pennsylvania, told Healio. “Separate from obesity, patients who have low oxygen saturation levels overnight are also at increased risk of developing blood clots.”

Researchers evaluated clinical outcomes of 31,309 patients (mean age, 50.4 years; 50.1% women) who were undergoing overnight polysomnography in six sleep laboratories at the University of Pittsburgh Medical Center from July 2004 to December 2018. The researchers assessed associations between OSA severity and incident VTE.

Michael V. Genuardi, MD, MS, FACC

During a mean follow-up period of 5.3 years, 1,791 incident VTE events, the primary outcome, occurred.

Every 10-event per hour increase in the apnea-hypopnea index was associated with a 4% increase in risk for incident VTE in age- and sex-adjusted analyses (HR = 1.04; 95% CI, 1.02-1.06). However, when the researchers adjusted for BMI, the association disappeared (HR = 1.01; 95% CI, 0.99-1.03).

The researchers reported an independent association with nocturnal hypoxemia and incident VTE. Patients with more than 50% sleep time spent with oxyhemoglobin saturation of less than 90% had a 48% increased risk for VTE compared with patients without nocturnal hypoxemia (HR = 1.48; 95% CI, 1.16-1.69).

According to the researchers, the association between elevated apnea-hypopnea index and risk for VTE may be largely explained by differences in patient adiposity.

“We found that patients who have low oxygen saturation levels overnight are at higher risk of VTE,” Genuardi said. “More research is needed to understand this risk factor, since it may broadly apply to patients with multiple underlying medication conditions, including obstructive and central sleep apnea, chronic lung disease, and congestive heart failure.”