Cigarette smoking is a well-known risk factor for a wide-range of diseases. Now, scientists have evidence that smoking may also increase the risk of age-related cataract, the leading cause of blindness and vision loss in the world.
Reported in Investigative Ophthalmology & Visual Science (Smoking and Risk of Age-related Cataract: A Meta-analysis), the new findings are the result of a meta-analysis conducted by a team of researchers from China.
"Although cataracts can be removed surgically to restore sight, many people remain blind from cataracts due to inadequate surgical services and high surgery expenses," said author Juan Ye, MD, PhD, of the Institute of Ophthalmology, Zhejiang University in China. "Identifying modifiable risk factors for cataracts may help establish preventive measures and reduce the financial as well as clinical burden caused by the disease."
The team performed the analysis using 12 cohorts and eight case-control studies from Africa, Asia, Australia, Europe and North America, to compare the prevalence of age-related cataract in individuals who ever smoked cigarettes to those who have never smoked. Further subgroup analyses were performed based on the subjects' status as a past or current smoker and the three subtypes of age-related cataract.
The results showed that every individual that ever smoked cigarettes was associated with an increased risk of age-related cataract, with a higher risk of incidence in current smokers. In the subgroup analysis, former and current smokers showed a positive association with two of the subtypes: nuclear cataract, when the clouding is in the central nucleus of the eye, and subscapular cataract, when the clouding is in the rear of the lens capsule. The analysis found no association between smoking and cortical cataract, in which the cloudiness affects the cortex of the lens.
While the overall analysis suggests that smoking cigarettes may increase the risk of age-related cataracts, the researchers point out that further effort should be made to clarify the underlying mechanisms.
"We think our analysis may inspire more high-quality epidemiological studies" said Ye. "Our analysis shows that association between smoking and the risk of age-related cataract differ by subtypes, suggesting that pathophysiologic processes may differ in the different cataract types."