Cataracts in the center of the eye's lens were three times as common among commercial pilots as among their peers who weren't pilots, write researchers from Iceland in the Archives of Ophthalmology.
Cosmic radiation -- a type of very energetic radiation originating from space -- is found throughout the universe. Flying puts pilots at greater exposure to cosmic radiation than most people.
Nuclear cataracts are the most common type of cataract. They're usually linked to aging. Cataracts are also tied to smoking, overexposure to ultraviolet radiation (including from sunbathing), eye injuries, diabetes, and long-term steroid use.
Some cataracts remain small and unnoticeable. Others severely hinder vision. Surgery can remove cataracts, but not all cataracts require surgery.
The study included 445 men, 79 of whom were commercial pilots. Most participants didn't have nuclear cataracts, but 79 men did.
Pilots were three times as likely to have nuclear cataracts as the nonpilots, after taking age, smoking, and sunbathing into account, write the researchers. They included Vilhjalmur Rafnsson, MD, PhD, of the preventive medicine department of the University of Iceland.
Cosmic Cataract Cause?
Based on the results, "cosmic radiation may be a causative factor in nuclear cataracts among commercial airline pilots," write the researchers.
Age also made nuclear cataracts more likely. Smoking and sunbathing weren't strongly linked to nuclear cataracts in this study.
Taking that all into account, the pilots' odds of getting nuclear cataracts were tied to their years as pilots and their cumulative radiation dose. Exposure before age 40 had the biggest impact. That's in line with the long time line for nuclear cataract development, write the researchers.
Eye injuries, diabetes, and long-term steroid use probably weren't important in this study, write Rafnsson and colleagues. Exposure to ultraviolet radiation in plane cockpits was "minimal," the researchers note.