Sociodemographic characteristics and risk factor analysis of Demodex infestation(Acari:Demodicidae)

To identify sociodemographic characteristics and risk factor of Demodex infestation,756 students aged 13-22 years in Xi'an,China were sampled for the school-based cross-sectional study.Demodex was examined using the cellophane tape method(CTP).The results showed that the total detection rate of Demodex was 67.6%.Logistic regression analysis revealed that five variables(gender,residence,sharing sanitary ware,frequency of face-wash per day,and use of facial cleanser) were found to be uncorrelated with Demodex infestation,whereas three variables(age,skin type,and skin disease) were found to be independent correlates.Students aged over 18 years had 22.1 times higher odds of Demodex infestation compared to those under 16 years and students aged 16-18 years also had 2.1 times higher odds compared to those aged 13-15 years.Odds of having a Demodex infestation for oily or mixed skin were 2.1 times those for dry or neutral skin.Students with a facial skin disease had 3.0 times higher odds of being infested with Demodex compared to those without.The inception rate of students with facial dermatoses increased in parallel with increasing mite count.The inception rates were 21.3%,40.7%,59.2%,and 67.7% in the negative,mild,moderate,and severe infestation groups,respectively(χ2=60.6,P<0.001).Specifically,the amount of infested mites and inception rate of acne vulgaris were positively correlated(R2=0.57,moderate infestation odds ratio(OR)=7.1,severe infestation OR=10.3).It was concluded that Demodex prevalence increases with age,and Demodex presents in nearly all adult human.Sebaceous hyperplasia with oily or mixed skin seems to favour Demodex proliferation.Demodex infestation could be associated with acne vulgaris.The CTP is a good sampling method for studies of Demodex prevalence.

A meta-analysis of association between acne vulgaris and Demodex infestation

Until now, etiology of acne vulgaris is still uncertain. Although clinicians usually deny the association between Demodex infestation and acne vulgaris, it has been proved in some clinical practices. To confirm the association between Demodex infestation and acne vulgaris, a meta-analysis was conducted. Predefined selection criteria were applied to search all published papers that analyzed the association between Demodex infestation and acne vulgaris (January 1950 to August 2011) in ISI Web of Knowledge, MEDLINE, and China National Knowledge Infrastructure (CNKI) databases. A meta-analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) based on fixed effects models or random effects models. We enrolled the 60 Chinese and 3 English papers in this meta-analysis, which covered Turkey and 25 different provinces/municipalities in China and 42 130 participants in-cluding students and residents, aged from 1 to 78 years. The pooled OR in random effects models is 2.80 (95% CI, 2.34-3.36). Stability is robust according to sensitivity analysis. The fail-safe number is 18 477, suggesting that at least 18 477 articles with negative conclusions would be needed to reverse the conclusion that acne vulgaris was related to Demodex infestation. So the effect of publication bias was insignificant and could be ignored. It was concluded that acne vulgaris is associated with Demodex infestation. This indicates that when regular treatments for acne vulgaris are ineffective, examination of Demodex mites and necessary acaricidal therapies should be considered.

Facial dermatosis associated with Demodex:a case-control study

Demodex has been considered to be related with multiple skin disorders,but controversy persists.In this case-control study,a survey was conducted with 860 dermatosis patients aged 12 to 84 years in Xi'an,China to identify the association between facial dermatosis and Demodex.Amongst the patients,539 suffered from facial dermatosis and 321 suffered from non-facial dermatosis.Demodex mites were sampled and examined using the skin pressurization method.Multivariate regression analysis was applied to analyze the association between facial dermatosis and Demodex infestation,and to identify the risk factors of Demodex infestation.The results showed that total detection rate of Demodex was 43.0%.Patients aged above 30 years had higher odds of Demodex infestation than those under 30 years.Compared to patients with neutral skin,patients with mixed,oily,or dry skin were more likely to be infested with Demodex(odds ratios(ORs) were 2.5,2.4,and 1.6,respectively).Moreover,Demodex infestation was found to be statistically associated with rosacea(OR=8.1),steroid-induced dermatitis(OR=2.7),seborrheic dermatitis(OR=2.2),and primary irritation dermatitis(OR=2.1).In particular,ORs calculated from the severe infestation(≥5 mites/cm2) rate were significantly higher than those of the total rate.Therefore,we concluded that Demodex is associated with rosacea,steroid-induced dermatitis,seborrheic dermatitis,and primary irritation dermatitis.The rate of severe infestation is found to be more correlated with various dermatosis than the total infestation rate.The risk factors of Demodex infestation,age,and skin types were identified.Our study also suggested that good hygiene practice might reduce the chances of demodicosis and Demodex infestation.