The impact of age, sex, blepharitis, rosacea and rheumatoid arthritis on Demodex mite infection.

Introduction: Two human-specific Demodex species have been described: Demodex folliculorum and Demodex brevis . A medical condition caused by the presence of Demodex is called demodicosis.

Material and methods: The study material comprised eyelashes collected from 1499 patients.

Results: Demodex sp. infection was revealed in 47% of patients (487 women and 216 men). We determined the following rates of infection by age groups: 1-25 (8% of infected subjects), 26-40 (36%), 41-55 (50%), 56-70 (67%), over 70 (77%). The sex of the subjects was not identified as a factor conducive to infection ( p = 0.108), while their age was positively correlated with the risk of infection ( p < 0.005). The 1499 study subjects included patients with blepharitis, rosacea, and rheumatoid arthritis. The study investigated the extent to which the above-mentioned conditions affect the risk of Demodex infection. Applying the method of logistic regression, the infection probability was estimated, depending on the age, sex, and comorbidities such as blepharitis, rosacea, and rheumatoid arthritis. Patients suffering from blepharitis were found to have a nearly 2.5-fold higher risk of Demodex infection than those without blepharitis, and the risk for rosacea patients was determined as three-fold higher than that of the general population.

Conclusions: Blepharitis and rosacea are risk factors for Demodex infection.