Associations of urine arsenic, blood manganese, and serum zinc with pterygium in Korean adults.

BACKGROUND

Pterygium, a fleshy growth of abnormal fibrovascular tissues on eye conjunctiva, is common in older adults. The mechanism underlying pterygium development is still unknown, but oxidative stress is considered one of the main causes. Arsenic (As), which is ubiquitous in nature, may adversely affect human health by inducing oxidative stress. On the other hand, manganese (Mn) and zinc (Zn) play an important role in enhancing the antioxidant system.

OBJECTIVE

We aimed to investigate the associations of As, Mn, and Zn with pterygium in general Korean adults using data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2010.

METHODS

The study population included 2832 adults from KNHANES 2008-2009 for As and Mn analyses and 1872 adults from KNHANES 2010 for Zn analyses (the only year for which serum zinc was measured). Pterygium was diagnosed as a wing-shaped fibrovascular growth using a slit-lamp. Environmental exposure levels of total As and As species were estimated by measuring their concentrations in urine. Mn and Zn were estimated by measuring in blood and serum, respectively.

RESULTS

The prevalence of pterygium was 4.9-5.6 %. After adjusting for confounding factors, the odds ratio (OR) for pterygium in the highest tertile (vs. the lowest) of total As levels in urine was 1.84 (95 % confidence interval (CI): 1.09-3.09). Total As levels had a dose-dependent association with pterygium (p-trend = 0.021). Urinary arsenobetaine levels were further adjusted to exclude the contribution of organic As from seafood intake, and the OR for pterygium became stronger but less significant (6.54 (95 % CI: 0.82-51.92)) in the subset with As species measured (n = 280). The OR for pterygium in the second tertile of Mn levels in blood was 0.53 (95 % CI: 0.34-0.84). There was no significant association between serum Zn and pterygium.

CONCLUSION

Our findings provide epidemiological evidence that excess As and deficient Mn may be associated with pterygium in Korean adults.