Susceptibility of patients with chronic obstructive pulmonary disease(COPD)to cardiovascular autonomic dysfunction asso-ciated with exposure to metals in ambient fine particles(PM2.5,particulate matter with aerodynamic diameter≤2.5 μm)remains poorly evidenced.Based on the COPDB(COPD in Beijing)panel study,we aimed to compare the associations of heart rate(HR,an indicator of cardiovascular autonomic function)and exposure to metals in PM2.5 between 53 patients with COPD and 82 healthy controls by using linear mixed-effects models.In all participants,the HR levels were significantly associated with interquartile range increases in the average concentrations of Cr,Zn,and Pb,but the strength of the associations differed by exposure time(from 1.4％for an average 9 days(d)Cr exposure to 3.5％for an average 9 d Zn exposure).HR was positively associated with the average concentrations of PM2.5 and certain metals only in patients with COPD.Associations between HR and exposure to PM2.5,K,Cr,Mn,Ni,Cu,Zn,As,and Se in patients with COPD significantly differed from those in health controls.Furthermore,association between HR and Cr exposure was robust in COPD patients.In conclusion,our fiindings indicate that COPD could exacerbate difference in HR following exposure to metals in PM2.5.