Association between the first occurrence of allergic conjunctivitis, air pollution and weather changes in Taiwan

Allergic conjunctivitis (AC) is one of the common allergic diseases, which may be influenced by environmental factors. This study was to examine the association between the first occurrence of AC, air pollution and weather changes, and demographic factors in Taiwan. A total of 100,636 eligible subjects were identified from the systematic sampling cohort database containing 1,000,000 insureds of the National Health Insurance of Taiwan from 2004 to 2013, and were matched with data from the environmental monitoring stations adjacent to their locations of clinics. The case-crossover design, using the same subjects experiencing exposures at the time of diagnosis for cases and that on the days one and two weeks before and after diagnosis for controls, was applied in the study. We found that the first occurrences of AC were significantly the most for youngsters by age (42.6%), for women by sex (56.2%), and in spring by season (29.6%) (P < 0.001). Multivariate conditional logistic regression analyses indicated that nitrogen dioxide (NO2), ozone (O-3), and temperature were positively associated with AC (P < 0.001), while relative humidity was negatively related to AC (P < 0.001). Knowing these associations, we suggest that AC patients pay attention to air pollution and weather change in the ambient environments and manage accordingly to mitigate the problems.