Seasonal patterns of ocular Demodex (Trombidiformes: Demodicidae) infestation and dry eye disease in a longitudinal urban cohort from Central Chile

Abstract

Evidence regarding seasonal variation in Demodex infestation and its association with dry eye disease (DED) remains limited. This study evaluated seasonal variation in Demodex infestation and DED and explored their relationship with environmental variables in a longitudinal cohort from Talca, Chile. A prospective longitudinal study was conducted among students and employees of Universidad Católica del Maule, Chile. Participants underwent ocular examinations during four seasonal evaluations (summer, fall, winter, and spring) over one year. DED was diagnosed according to TFOS DEWS II criteria, and Demodex infestation was assessed by eyelash epilation and quantified using an infestation index. Temperature, relative humidity, PM10, and PM2.5 were obtained from a local meteorological station. Seasonal differences were analyzed using repeated-measures statistical tests. Seventy-seven participants were enrolled, of whom 55 completed all four evaluations. Significant seasonal variation was observed in Demodex infestation prevalence (P = 0.035), infestation index (P < 0.001), DED prevalence (P = 0.043), and OSDI score (P < 0.001). Demodex infestation burden peaked during fall, whereas DED prevalence and symptom severity were highest during spring. Although environmental conditions differed significantly across seasons, no climatic variable was independently associated with either Demodex infestation or DED. Ocular Demodex infestation and DED exhibited distinct seasonal patterns. Seasonal variation was more evident for infestation burden than prevalence, suggesting that quantitative measures provide a more sensitive indicator of seasonal changes in Demodex populations. These findings support a multifactorial influence of seasonal environmental conditions on ocular surface health, rather than effects attributable to individual climatic variables.