Associations between air pollution and daily outpatient visits for dry eye disease and the effect modification of temperature.

Abstract

Background: Dry eye disease (DED) is one of the most common ocular surface disorders caused by various contributors. Air pollutants are considered a risk factor for ocular surface diseases. We aimed to investigate the associations between air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃) and PM_2.5 constituents and daily outpatient visits for DED, as well as the modifying effect of temperature on the associations.

Methods: Daily data on DED outpatient visits and environmental variables during 2014-2019 were collected in Hangzhou, China. Distributed lag nonlinear models (DLNM) combined with time-stratified case-crossover design were utilized to evaluate the effects of air pollutants and PM_2.5 constituents on DED daily outpatient visits during 0‒3 lag days. Furthermore, we also estimated the modification effect of temperature stratified by median. The attributable fraction (AF) of air pollutants and PM_2.5 constituents on DED outpatient visits were quantified. Stratified analyses of gender, age, and seasons were conducted to assess vulnerable population characteristics and high-risk periods.

Results: Every interquartile range increase in PM_2.5, PM₁₀, NO₂, SO₂ and CO concentration were significantly associated with daily DED cases. The AF were 6.42% (95% CI: 1.09%, 11.58%), 8.00% (2.60%, 13.60%), 18.65% (11.52%, 25.21%), 10.82% (3.92%, 17.24%) and 12.28% (0.23%, 22.86%), respectively. For PM_2.5 constituents, NO₃^- and NH₄⁺ were associated with DED, with AF of 4.34% (0.21%, 8.11%) and 4.84% (0.18%, 9.09%), respectively. The effects of air pollution were significant in low-temperature level for PM_2.5, PM₁₀, NO₂, SO₂, and CO; while the effects were statistically insignificant in high-temperature level. Subgroup analyses indicated significant associations were present in winter and among patients aged 21-40 but insignificant in other seasons and age groups.

Conclusion: Our results revealed that air pollutants were associated with DED outpatient visits. Low temperatures might increase the hazardous effects of air pollution. Besides, individuals aged 21-40 were vulnerable to air pollution, and winter was the high-risk period.

Clinical trial number: Not applicable.