Role of Temperature Change, Ambient Temperature, and Relativ
This study examined associations between several meteorological conditions, including temperature variation, and AC visit risk. Studies have implicated temperature and humidity in the pathogenesis of allergic conjunctivitis (AC), as these conditions facilitate air particulate and aeroallergen dispersion and tear film instability. Research also suggests that variation in temperature associates with risk of asthma.

Data on people who have been diagnosed with AC was gathered. All cases were given a random control date 90-250 days prior to diagnosis, using a case-crossover design. For 30 day lags, daily time-lagged exposures were calculated. At the national level and throughout domestic climate regions, the correlations between temperature, temperature variation, relative humidity (RH), and temperature-RH interaction with visit risk were investigated using multivariate logistic regression models.

--Overall, 74,951 subjects made 116,162 visits for AC. Prevalence was highest in spring (more than 10% April-May) in the Northeast (NE) and Southeast (SE) (more than 15%), and lowest in winter (less than 6.1% December-February) in the Pacific Northwest (PNW) (less than 5%).

--AC visit risk was positively associated with temperature, SD of temperature, and temperature-RH interaction, whereas it was negatively associated with RH.

--Regionally, the Pacific Northwest, Northeast, and Lower Midwest (LMW) accounted for the strongest associations.

Finally, temperature, temperature variation, and RH were found to be associated with the risk of allergic conjunctivitis visits. Northern areas, such as the Pacific Northwest, had the most observed correlations.