Asthma is one of most common chronic burdens for population in Taiwan. Inhaled steroids are the preferred prescription for long-term control of the asthmatic symptom and exacerbation prevention. Cataract has been reported as one of the adverse side effects of the medication, but the association remains unclear. There are scant of data on the association between steroid use and cataract for Chinese population. This study used a large population-based insurance claims dataset to investigate the risk of cataract for patients who had used corticosteroids for the control of asthma.
We conducted a retrospective cohort study using data obtained from the National Health Insurance program (NHI) of Taiwan. Using 903,183 individuals insured in 1997 as a cohort. We first calculated the prevalence and incidence rates annually through 2008 for asthma and cataract. We then established an asthma cohort and non-asthma cohort using 1997 population to investigate whether the risk of cataract was greater in asthma cohort than in non-asthma cohort. We further identified asthma subjects from outpatient visits for patients without previous history of corticosteroid. Among 84,339 asthma patients newly diagnosed in 1998-2008, we found 3880 patients without the history of corticosteroid use for other illnesses. Follow-up analyzed showed that 1120 persons were steroid users and 2760 persons were non-users of any steroid.
The Cox proportional hazard regression analysis was used to estimate the hazardous ratio (HR) of cataract associated with asthma, after controlling for sex, age, diabetes mellitus, hypertension, glaucoma, and gout. The incidence of cataract was 1.5-fold (69.2 vs. 46.8 per 1000 person-years) higher in the asthma cohort than in the non-asthma cohort with the adjusted hazard ratio of 1.36 (95% confidence interval (CI): 1.30-1.42). Comorbidities of diabetes and glaucoma are also significant factors predict the risk of cataract for the asthmatic patients in the Cox regression analysis.
Further investigation comparing between asthmatics patients using corticosteroids and not using showed that steroid users were at a 30% increased risk of cataract. Among the steroid users, women were at higher risk than men (7.50 vs. 4.43 per 1000 person-years). Patients with the oral intake of steroids with the accumulative dose of > 90 mg had a HR of 2.61 (95% CI= 1.64-4.15). No association was found in those had inhaled corticosteroids.
In conclusion, higher doses of oral exposure to corticosteroids are associated with an increased risk of cataract. The dosage may not large enough to cause an adverse effect among users of inhaled corticosteroids.
