People who smoke are twice as likely to suffer from age-related macular degeneration, the leading cause of blindness in the elderly, a British study found.
Researchers at the London School of Hygiene and Tropical Medicine looked at data from more than 4,000 Britons who were 75 years of age or older and who participated in a wide-scale study on health care and the elderly. As part of the study, participants were given a vision test, which allowed the researchers to divide subjects into two groups: people whose vision was impaired to due macular degeneration and a control group of people who had no vision problems. Participants in the main study who had vision problems caused by other health conditions were not included in the smoking study.
Macular degeneration occurs when the macula, the small, central part of the retina, is damaged. Macular degeneration is classified as either dry, which is when the tissue of the retina shrinks and pigment accumulates inside it, or wet. Wet macular degeneration occurs when new blood vessels grow around and behind the macula, eventually causing scarring inside the eye and subsequent vision problems. Dry macular degeneration accounts for about 80% of all cases.
In the study, the researchers did not distinguish between people with wet and dry macular degeneration. Participants were questioned on their smoking habits by an interviewer. They were asked whether they currently smoked, and if so, how much, as well as whether they had ever smoked and when they had quit.
In their analysis, the researchers also looked at participants’ socioeconomic status and their history of alcohol consumption and cardiovascular disease, which is a known risk factor for macular degeneration. Other risk factors such as low dietary intake of nutrients, family history of macular degeneration, and exposure to sunlight – all of which have been shown to play a role in the development of this condition – were not considered because of a lack of data.
After accounting for those factors, the researchers found current smokers to be twice as likely as non-smokers to develop macular degeneration. People who had been smokers within the past 20 years also had an increased risk, while people who had quit smoking 20 or more years ago had the same risk as people who never smoked.
The study, which was published in the British Journal of Ophthalmology, is not the first to link smoking to macular degeneration, but it is one of the largest examining this association.