Clinical significance of comorbidities in idiopathic pulmonary fibrosis and hypersensitivity pneumonitis

Comorbidities are important factors influencing the course and prognosis of interstitial lung diseases (ILDs). However, comparative data on the structure and clinical significance of comorbidities in idiopathic pulmonary fibrosis (IPF) and hypersensitivity pneumonitis (HP) remain limited.

The aim was to assess the prevalence and clinical significance of comorbidities in patients with IPF and HP.

Methods. This single-center prospective observational study included 621 patients (229 with IPF, 392 with HP) with a 12-month follow-up. Clinical, demographic, functional, and radiological characteristics, comorbidities, the Charlson Comorbidity Index (CCI), and the GAP (Gender, Age, Physiology) index were analyzed. All patients underwent pulmonary function testing, the 6-minute walk test (6MWT), echocardiogram, and high-resolution computed tomography scan of the chest.

Results. Most patients (66.2%) had 1 – 3 comorbidities, while 19.6% had ≥ 4 comorbidities. Patients with IPF had significantly higher CCI scores than those with HP (p < 0.001). The most common comorbidities were hypertension, cardiovascular disease (CVD), gastroesophageal reflux disease, pulmonary hypertension, and diabetes mellitus. Emphysema and obstructive airway diseases were more frequent in IPF (p < 0.05). A higher comorbidity burden and higher CCI scores correlated with higher GAP scores, shorter 6MWT distance, and more severe dyspnea (mMRC scale). The presence of ≥ 2 comorbidities was associated with increased mortality risk (AUC 0.587, p = 0.01), as was CCI ≥ 4 (AUC 0.608, p = 0.002; log-rank p = 0.007). CVD was associated with greater functional impairment and reduced exercise tolerance, while diabetes mellitus was an independent adverse prognostic factor, particularly in HP (OR 2.58, p = 0.016).

Conclusion. Comorbidities are highly prevalent in both IPF and HP and significantly influence disease course and prognosis. Assessment of comorbidity burden, including the CCI, may serve as an additional risk-stratification tool in patients with fibrosing ILDs.

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