Passive smoking can increase a person's risk of developing age-related macular degeneration, suggest UK study findings.
Smoking has previously been identified as a risk factor for age-related macular degeneration, one of the most common causes of visual impairment in Western countries.
However, the latest study shows that while smokers have up to triple the normal risk of developing the condition, non-smokers who live with smokers have double the normal risk.
Exposure to smoke increased the risk of both forms of the disease – geographic atrophy (GA) and choroidal neovascularisation (CNV) – it is reported in the latest issue of the British Journal of Ophthalmology.
But among smokers who had given up 20 years previously, the risk of developing age-related macular degeneration was comparable to non-smokers.
"This is another reason why smoking should be discouraged and those who do smoke should be encouraged to stop," said Professor John Yates, from the University of Cambridge, and colleagues.
"The benefits of giving up smoking applied to both CNV and GA."
For the study, 435 people with end-stage age-related macular degeneration and 280 partners who lived with them, were assessed for the condition and smoking history.
The researchers found there was a strong correlation between number of pack-years of smoking and risk of developing age-related macular degeneration, with more than 40 pack years of smoking associated with an odds ratio of 2.75.
Smoking for more than 40 pack-years was specifically associated with odds ratios of 3.43 and 2.49 for GA and CNV, respectively. Additionally, passive smoking was associated with an increased risk of age-related macular degeneration, with an odds ratio of 1.87.
"This provides strong support for a causal relationship between smoking and age-related macular degeneration," said Professor Yates et al.
"Stopping smoking appears to reduce the risk of both GA and CNV; this needs to be emphasised as a public health issue."
Anita Lightstone, head of eye health at the Royal National Institute of the Blind (RNIB), commented: "This is an extremely important finding and further evidence to back RNIB's call for a ban on smoking in all enclosed public places and work places across the UK."
Useful Links
British Journal of Ophthalmology
University of Cambridge
Royal National Institute of the Blind