biostudies-literatureDu YScientific Research Foundation for Scholars of Hangzhou Normal UniversityZhejiang Provincial Natural Science Foundation of ChinaNational Natural Science Foundation of China4169https://www.ebi.ac.uk/biostudies/studies/S-EPMC12659098biostudies-literatureUnknown25(1)<h4>Background</h4>Limited evidence exists on the relationship between social isolation and lung function, with few studies exploring underlying mechanisms. This study examined the association between social isolation and lung function decline, and the mediating roles of smoking, income, physical activity, and BMI in U.S. and Chinese populations.<h4>Methods</h4>This study utilized data from adults aged ≥ 45 years in NHANES (2007-2012, cross-sectional) and CHARLS (2011 and 2015, longitudinal). Lung function metrics from NHANES included Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), and Peak Expiratory Flow (PEF), while CHARLS provided PEF data. Social isolation was assessed using marital status, living alone, and social participation in both studies, with NHANES includBMC public healthSocial isolation and lung function in middle-aged and older adults: identifying modifiable pathways across two populations.PMC12659098No. 4265C50223204066No. 82302180No. LQ24G030003No. 72404076Yuan CNi XRan XMa HCui XDu YZhao ZDing LfalseSocial isolation and lung function in middle-aged and older adults: identifying modifiable pathways across two populations.<h4>Background</h4>Limited evidence exists on the relationship between social isolation and lung function, with few studies exploring underlying mechanisms. This study examined the association between social isolation and lung function decline, and the mediating roles of smoking, income, physical activity, and BMI in U.S. and Chinese populations.<h4>Methods</h4>This study utilized data from adults aged ≥ 45 years in NHANES (2007-2012, cross-sectional) and CHARLS (2011 and 2015, longitudinal). Lung function metrics from NHANES included Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), and Peak Expiratory Flow (PEF), while CHARLS provided PEF data. Social isolation was assessed using marital status, living alone, and social participation in both studies, with NHANES includ2025-01-01T00:00:00Z2025 Nov2026-06-05T21:35:59.286Z2026-05-22T03:14:43.889ZS-EPMC126590984129948810.1186/s12889-025-25292-6