This study aimed to clarify the relationship between physical activity at the time of home oxygen therapy (HOT) initiation and subsequent prognosis in patients hospitalized with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD).
A retrospective cohort study was conducted, including 91 patients (61 males, 30 females) diagnosed with COPD and ILD who were hospitalized and initiated on HOT and respiratory rehabilitation at our institution between 2019–2024. Data collected included physical function (6-minute walk test: 6MWT, Frailty Index, independence in activities of daily living), respiratory function (FEV1, FVC, %FVC, %FEV1), nutritional status (Geriatric Nutritional Risk Index: 14.89＊Albumin + 41.7 + BMI/22), comorbidities, and left ventricular ejection fraction (LVEF). Patients were divided into two groups (survivors and non-survivors) over a 5-year observation period, and various parameters were statistically compared. Univariate analysis was performed using the log-rank test. The Cox hazards analysis was used to evaluate factors associated with 1500-day mortality.
All-cause mortality occurred in 22 ILD patients (24.1%) and 13 COPD patients (14.2%) (p 0.001). Ten patients (10.1%) had lung cancer, and ILD patients were primarily treated with immunosuppressants and steroids. Multivariable Cox regression analysis identified activities of daily living (functional independence measures) as a significant risk factor for mortality (HR, 0.98; 95% CI, 0.98-0.99; p = 0.01). ADL on admission, with a cutoff value of 84 points, was independently associated with all-cause mortality risk. The log-rank test revealed a significantly higher mortality rate in ILD patients, particularly in those with an ADL score below 84 points.
As chronic respiratory diseases progress, they increasingly limit physical activity. Prognostic factors for these conditions include walking distance, oxygen desaturation during physical activity, and dyspnea. ILD is more likely than COPD to result in significant oxygen desaturation during exercise, leading to more frequent dyspnea and reductions in ADL. In addition, ILD is associated with a higher incidence of lung cancer, and side effects from medications are also thought to contribute to poor outcomes.
This study suggests that ILD patients with low ADL scores at the initiation of HOT are likely to have a poor prognosis, emphasizing the importance of preparing for end-of-life care.
ILD patients receiving HOT with an ADL score of 84 points at hospital discharge should be considered at high risk for poor outcomes and may require preparation for end-of-life care.
Activities of daily living
Frailty
