Joint associations of long-term exposure to fine particulate constituents and muscle strength with cardiovascular diseases: a nationwide cohort study in China

Research has indicated that PM_2.5 exposure and low muscle strength may increase the risk of cardiovascular diseases (CVDs). However, inconsistent findings existed on PM_2.5 constituents and CVDs, and little is known about the interplay between PM_2.5 constituents and muscle strength. This study aimed to examine the associations of PM_2.5 and its components with the incidence of CVDs and to further investigate the joint effects of pollutants and muscle strength on CVDs in a nationwide cohort from 2011–2018. PM_2.5 and five constituents, including black carbon (BC), organic matter (OM), sulfate (SO₄²⁻), nitrate (NO₃⁻), and ammonium (NH₄⁺), were obtained from established spatiotemporal models and evaluated annually within the follow-up period. A time-varying Cox model was employed to investigate the impact of long-term exposure to PM_2.5 and its components on CVDs. The joint effects on CVDs were examined under exposure to both pollutants (high vs. low) and muscle strength (normal vs. low). During the 7-year follow-up, 1971 cases of CVD occurred among the 10,413 participants. Significant associations of CVDs with a one standard deviation increase in each pollutant were observed, with HRs (95 % CIs) of 1.15 (1.09, 1.21) for PM_2.5, 1.17 (1.11, 1.24) for OM, 1.16 (1.09, 1.22) for BC, 1.13 (1.07, 1.19) for NH₄⁺, 1.14 (1.08, 1.19) for NO₃⁻ and 1.13 (1.07, 1.19) for SO₄²⁻. Higher risks of CVDs were obtained in participants exposed to high levels of PM_2.5 constituents and low muscle strength. These findings suggest that reduced muscle strength may enhance the effects of PM_2.5 constituents on cardiovascular damage.