Influence of climate factors on pediatric alopecia areata flares in Philadelphia, Pennsylvania.

Patients with alopecia areata (AA) may experience episodic disease flares characterized by increasing hair loss that follow a seasonal pattern. However, no studies have examined whether specific climate factors contribute to the seasonal pattern of AA flares. Using Spearman rank correlation analyses, we assessed the association between climate variables and AA flare frequency per month in 336 children with AA in Philadelphia, Pennsylvania. Region-specific monthly values for average ambient temperature, air pressure, cloudiness, hours of sunlight, relative humidity, number of days with sun, number of days with rain, volume of precipitation, wind gust, wind speed, and UV index from January 2015 to December 2017 were obtained from World Weather Online. We found significant (P < 0.05) correlations between AA flare frequency and UV index (R = - 0.66), precipitation (R = - 0.66), number of days with rain (R = - 0.70), number of days with sun (R = 0.62), and air pressure (R = 0.80). Stratified analyses showed even stronger associations with UV index and precipitation in patients with an atopic comorbidity. New significant correlations appeared with temperature, wind speed, and UV index of the prior month. However, in patients who did not have atopic comorbidities, we generally observed weaker and non-significant correlations between climate and AA flare frequency. This study suggests that certain climate factors may mediate the seasonal pattern of AA flares and may contribute to AA pathogenesis. Atopic AA patients may be more susceptible to the influence of climate compared to those with no history of atopy.