Researchers have developed a nomogram for predicting obstructive sleep apnea (OSA) in patients with pulmonary arterial hypertension (PAH). The research used to create and validate the nomogram was reported in Nature and Science of Sleep.

Recognizing that OSA often occurs in patients with PAH, whose condition may worsen due to OSA, researchers sought to create a model for predicting the occurrence of OSA in patients with PAH, thus enabling early identification and treatment of OSA in these patients.

The study enrolled patients who were diagnosed with PAH via right-heart catheterization (RHC) and had complete cardiorespiratory polygraphy (PG) data available from May 2020 to November 2021 at a center in the People’s Republic of China. The cardiorespiratory PG analysis was conducted within 7 days prior to or following the RHC procedure.

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Demographic data, fasting venous blood samples, and biochemical parameter measurements were obtained, and the degree of daytime sleepiness was assessed with the Epworth Sleepiness Scale (ESS) questionnaire. All patients had a full night of cardiorespiratory PG monitoring.

A total of 258 patients with PAH were included in the final analysis (mean age, 43 ± 16 years; 54% female). Of the cohort, 3.1% reported excessive daytime sleepiness (ESS >10), and 69 patients (26.7%) met the diagnostic criteria for OSA — 53 (76.8%) with mild OSA and 16 (23.2%) with moderate-to-severe OSA.

Patients with PAH were divided into 2 groups — those with OSA (n=69; mean age, 50.6 ± 16.5 years; 50.7% male) and those without OSA (n=189; mean age, 39.6 ± 14.5 years; 56.1% female). The OSA group had a higher body mass index (BMI) score, poorer respiratory characteristics, and a higher proportion of comorbidities such as hypertension, diabetes, and hyperlipidemia, compared with the non-OSA group (P <.05).

Using multivariable logistic regression, the researchers developed a nomogram incorporating 6 factors (age, BMI, hypertension, glycated hemoglobin, uric acid, and interleukin-6). The nomogram was validated with 1000-bootstrap analysis. The C-index was 0.760, and the corrected C-index was 0.738, exceeding 0.7 in both cases, which indicates a satisfactory performance. In receiver operating characteristic analysis when the cutoff value of the apnea-hypopnea index was 5 events/hour, the area under the curve for the nomogram was 0.760. Compared with the ESS (AUC=0.528), the nomogram had a better predictive value (P <.001).

Because the number of patients with moderate-to-severe OSA was too small to support a model with 6 predictors, the prediction value for moderate-to-severe OSA of the model was not validated.

Decision curve analysis findings on a visual basis confirmed that the nomogram had superior overall net benefits within a wide range of practical threshold probability.

The study is limited by its single-center design, retrospective nature, and sample size. Also, cardiorespiratory PG was used in the sleep evaluation instead of diagnostic polysomnography, which could lead to an underestimation of OSA prevalence. In addition, validation of the test was conducted in patients from the same institution, which limits generalizability of results to other PAH populations.

“The nomogram developed and validated in this study may facilitate an early identification of OSA in PAH patients with satisfactory performance and discrimination,” concluded the researchers.


Hu M, Duan A, Huang Z, et al. Development and validation of a nomogram for predicting obstructive sleep apnea in patients with pulmonary arterial hypertension. Nat Sci Sleep. Published online August 9, 2022. doi:10.2147/NSS.S372447