Associations of ambient ozone exposure and CD4⁺ T cell levels with mortality among people living with HIV: An eight-year longitudinal study

There has been a consistent upward trend in ground-level ozone (O-3) concentration in China. People living with HIV (PLWH) may be more vulnerable to the health impacts of O-3 exposure due to their immunosuppressed state. This study aims to investigate the association between ambient O-3 exposure and mortality among PLWH, as well as the potential exacerbating effects of a decreased CD4(+) T cell level. Daily maximum 8-hour O-3 concentrations were assigned to 7270 PLWH at a county level in Guangxi, China. Every 10-unit increase in ambient O-3 concentration was associated with a significant rise in all-cause mortality ranging from 7.3 % to 28.7 % and a significant rise in AIDS-related mortality ranging from 8.4 % to 14.5 %. When PLWH had a higher CD4(+) count (>= 350 cells/mu L), elevated O-3 concentration was associated with increased blood CD4(+) count at lag0 [percent change with 95 % confidence interval, 0.20(0.00, 0.40)], lag1 [0.26(0.06, 0.47)], and lag2 [0.23(0.03, 0.44)]; however, an opposite association was observed when CD4(+) count was <350 cells/mu L for half-year average [-2.45(-4.71, -0.14)] and yearly average [-3.42(-5.51, -1.29)] of O-3 exposure. The association of O-3 exposure with all-cause and AIDS-related mortality was more prominent among those with higher CD4(+) count. Exploratory analysis revealed possible associations between O-3 exposure and respiratory infections and clinical symptoms. These findings suggest potential synergistic effects between a compromised immune status and elevated O-3 exposure levels on mortality risk among PLWH. Ambient O-3 exposure should be considered as an emerging mortality risk factor for PLWH in the era of antiretroviral therapy, requiring further attention from researchers and healthcare professionals.