Air pollution and tear lactoferrin among dry eye disease modification by stress and allergy: a case–control study of taxi drivers

Few studies have explored the possible associations between air pollution and tear lactoferrin (Lf) levels, a non-invasive biological marker of ocular surface diseases, among taxi drivers, while none have explored the modifications by of stress and allergic tendencies in the relationship. We recruited 1,905 taxi drivers with dry eye disease (DED) and 3,803 non-DED controls in Liaoning, China, 2012–2014. After physical examination and questionnaires were recorded, ocular surface were measured and tear Lf was determined by electrophoresis. Air pollutants and humidity were estimated by measured concentrations from monitoring stations. Conditional logistic regression models were employed to examine the associations of air pollutants and humidity with tear Lf levels. Among taxi drivers with stress or allergic tendencies, with an IQR (26 µg/m 3 , 10 µg/m 3 ) increase in PM 10 and NO 2 levels, adjusted odds ratio was elevated by 1.89 (95% CI, 1.19 to 3.08) or 1.77 (95% CI, 1.06 to 2.90), and 2.87 (95% CI, 1.60 to 3.58) or 2.93 (95% CI, 1.64 to 3.83), respectively. In contrast, humidity was inversely associated for taxi drivers with stress [0.51 (95% CI, 0.38 to 0.64)] or allergic tendencies [0.49 (95% CI, 0.11 to 0.84)] and taxi drivers without stress [0.33 (95% CI: 0.17, 0.39)] or without allergic tendencies [0.39 (95% CI, 0.19 to 0.59)]. Tear Lf was negatively associated with each quartile of PM 10 or NO 2 exposure, and low humidity. PM 10 , NO 2 , and low humidity were inversely associated with Lf levels, especially for DED taxi drivers with stress and allergic tendencies.