Smoking cigarettes, or living with someone who does, increases a person's risk of developing a progressively degenerative eye disease known as age-related macular degeneration or AMD, according to a study conducted in the UK.
"Smoking puts you at increased risk of losing your sight in old age and the more you smoke the higher the risk," Dr. John Yates from the University of Cambridge told Reuters Health. "Smoking also increases the risk for the people living with you. So these are two good reasons to stop smoking."
AMD is the leading cause of reduced vision and blindness in many European countries and the U.S. A person's risk of developing the disease increases with age.
Researchers have tried over the years to define avoidable risk factors in a bid to reduce the burden of AMD. Some but not all studies have suggested that smoking is one such modifiable risk factor. Less is known about the risk of the disease in non-smokers breathing second-hand smoke.
To investigate, Yates and others studied 435 people with advanced AMD and 280 partners who lived with them. They used a detailed questionnaire to gather information on their smoking history.
The team reports in the British Journal of Ophthalmology that the more a person smoked, the greater the odds of developing AMD. People who smoked a pack or more a day for 40 years had triple the risk of developing the eye disease compared with those who did not smoke.
"Previous studies," Yates noted, "have shown that smoking increases the risk of age-related macular degeneration, so we expected our study to confirm that. In addition, we've shown that it's the amount smoked that matters."
Kicking the habit significantly lowered the risk of AMD. "In our study the risk for people who had stopped smoking fell to the same level as nonsmokers after 20 years," Yates told Reuters Health.
The risk of AMD was also increased in household partners of smokers. Their risk was nearly doubled, the team reports.
"One previous study," Yates said, "raised the possibility that passive smoking might increase the risk but did not reach statistical significance. Our study did show a statistically significant effect of passive smoking, and ... that was a bit of a surprise."