Association between cold spells and chronic lung disease: a nationwide spatial machine learning analysis

To investigate the longitudinal association between baseline cold spells and the risk of incident chronic lung disease (CLD) among middle-aged and elderly adults in China, and to characterize its spatial distribution and multifactorial context.

Using national data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2020), Cox proportional hazards models, logistic regression, stratified analysis and sensitivity analyses were employed to analyze the impact of nine differently defined cold spell indicators on the risk of new-onset CLD in adults aged ≥45 years. Geographically Gaussian process regression (GGPR) mapped spatial disease distribution, and GeoShapley decomposition quantified factor contributions.

In Cox models, baseline cold spell exposure was associated with a modestly elevated risk of incident CLD (fully adjusted hazard ratios [HRs] ranged from 1.10 to 1.13). This positive association was further supported by logistic regression analyses (fully adjusted odds ratios [ORs]: 1.11-1.13) and sensitivity analyses. After correction for multiple comparisons, urban residence, higher education, and cancer history modified the association. Spatial prediction models (GGPR) identified northern China as a consistent high-risk region across all nine cold spell definitions (validation AUC: 0.7077-0.7129). Notably, GeoShapley analysis revealed that air pollutants and geographic coordinates contributed more substantially to spatial prediction than did cold spell exposure, indicating that regional background factors dominate the spatial patterning of CLD risk.

Higher baseline cold spell exposure was associated with a modestly increased risk of incident CLD among Chinese adults aged ≥45 years, with northern China identified as a consistent high-risk region. The independent longitudinal association of cold spells, though not dominant in spatial prediction models, highlights their potential role as an environmental trigger warranting further investigation.