Macular degeneration results in a gradual distortion of central vision, and sometimes leads to a central blind spot called a scotoma. When central vision is impaired, one may have difficulty recognizing faces and colours, driving a car, reading or doing close handwork, such as sewing or other handcrafts.
The study was conducted by a team of researchers led by Jennifer S. L. Tan at University of Sydney and Westmead Hospital, Sydney, Australia.
As part of the study researchers examined 2,454 Australians age 49 and older to study the association between smoking and the 10-year incidence of AMD, as well as the possible links between smoking and other common risk factors.
The participants answered a food frequency questionnaire and had retinal photos taken at five-year and 10-year follow-up exams. An interviewer-administered questionnaire assessed participants' smoking status. BMI and blood pressure were also measured.
The study found that current smokers were four times more likely to develop age-related macular degeneration and past smokers were three times as likely to have geographic atrophy, an advanced form of the disease, than those who had never smoked.
"Joint exposure to current smoking and (1) the lowest level of high-density lipoprotein (HDL) [good] cholesterol, (2) the highest total to HDL cholesterol ratio, or (3) low fish consumption was associated with a higher risk of late AMD than the effect of any risk factor alone. However, interactions between smoking and HDL cholesterol level, ratio of total to HDL cholesterol and fish consumption were not statistically significant," the authors wrote.
"In summary, the findings from this large population-based prospective study add evidence to a possible causal relationship between smoking and the long-term risk of late, but not early, AMD," the authors concluded.
The findings of the study were published in the July issue of Archives of Ophthalmology, one of the JAMA/Archives journals.