Introduction:
Interstitial lung disease (ILD) comprises a heterogeneous group of disorders characterized by progressive lung fibrosis, respiratory failure, and substantial mortality, particularly among older adults. While prior studies have described historical ILD mortality trends, comprehensive analyses incorporating future projections, detailed geographic disparities, and socioeconomic variation remain limited.

Material and methods:
We analyzed CDC WONDER underlying-cause-of-death data for US adults aged ≥ 65 years from 1999 to 2020. ILD deaths were identified using ICD-10 code J84, and age-adjusted mortality rates (AAMRs) per 100,000 population were calculated using the 2000 US standard population. Joinpoint regression was used to identify turning points in mortality trends, autoregressive integrated moving average (ARIMA) modeling was used to project AAMRs through 2030, and Socio-demographic Index (SDI)-based correlation and frontier analyses were used to evaluate geographic and socioeconomic disparities in ILD mortality.

Results:
A total of 305,452 ILD deaths were recorded among US adults aged ≥ 65 years, with an overall AAMR of 33.45 per 100,000 population. Mortality increased significantly from 1999 to 2006 and then stabilized through 2020, with ARIMA models projecting continued stability through 2030. Significant disparities persisted, with mortality rates highest among males, American Indian or Alaska Native populations, Hispanic or Latino individuals, and residents of Western and Midwestern states. State-level analyses showed that lower SDI was generally associated with higher AAMR, with several states exhibiting excess mortality relative to their socioeconomic development levels.

Conclusions:
Although ILD mortality among older US adults stabilized after the mid-2000s and is projected to remain stable through 2030, substantial disparities persist across sex, race/ethnicity, geography, and socioeconomic context. These findings suggest that future reductions in ILD mortality may depend less on broad population-level declines and more on targeted strategies focused on high-burden groups and regions.