Ambient PM2.5 and O3 and their combined effects on prevalence of presbyopia among the elderly: A cross-sectional study in six low- and middle-income countries

Abstract

Background: Ambient air pollutant directly contacts with the eyes, however, the effect of ambient fine particulate matter (PM_2.5) and ozone (O₃) on vision impairment, such as presbyopia, has been kept largely unknown.

Methods: We surveyed a total of 36,620 participants aged 50 years and above in six low- and middle-income countries. Ambient annual concentrations of PM_2.5 and O₃ for the residential community were estimated using satellite data and chemical transport model. A mixed effects model was utilized to assess the effects of ambient PM_2.5 and O₃ on presbyopia, as well as their combined effects.

Results: A total of 13,841 presbyopia cases were identified among the participants with a prevalence rate of 41.17%. For both PM_2.5 and O₃, we found a J-shaped exposure-response relationship with the threshold being identified at 15 μg/m³ for PM_2.5 and 55 μg/m³ for O₃. The odds ratio (OR) of presbyopia was 1.15 (95% CI: 1.09, 1.21) for each 10 μg/m³ increase in PM_2.5 above 15 μg/m³ and 1.37 (95% CI: 1.23, 1.54) for O₃ above 55 μg/m³ after adjusting for various potential confounding factors. There appeared to be a synergistic interaction between ambient PM_2.5 and O₃ on presbyopia in the additive model, the combined effect was significantly larger than the sum of their individual effects, with a synergistic index of 2.39.

Conclusion: This study supports that exposures to ambient PM_2.5 and O₃ might be important risk factors of presbyopia among old adults, and simultaneously exposure to high level of the two pollutants could intensify their individual effects.

Keywords: Air pollution; Low- and middle-income countries; O(3); PM(2.5); Presbyopia.