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Study: Smoking increases risk of
blindness in elderly
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.
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