A new long-term study has found that people who smoke, or have smoked a large number of cigarettes in the past, are more likely to develop age-related macular degeneration or to have it increase in severity sooner. The findings were published in the August edition of the journal Ophthalmology by researchers at the University of Wisconsin School of Medicine and Public Health.
Age-related macular degeneration (AMD) is a common eye disease that results in damage to the central part of the retina (the light-sensitive layer of tissue on the inside back wall of the eyeball) and is a leading cause of blindness among individuals over the age of 50. It is generally caused by abnormal blood vessels that leak fluid or blood into the region of the macula. A current theory is that smoking might damage blood vessels that nourish the retina, leading to an increased risk of worsening of macular degeneration, or that smoking might deposit toxins within retina tissue that damage its function.
The researchers conducted a study to assess the association of current cigarette smoking and pack-years smoked with the incidence and progression of AMD and to examine the interactions of current smoking and pack-years smoked. The study group comprised 4,439 individuals who resided in a representative American community. The researchers used data from the Beaver Dam Eye Study, which began in 1988 and included nearly 5,000 adult residents of Beaver Dam, Wisconsin. Eye examinations were performed every 5 years over a 20-year period. They also examined whether the participants possessed genetic risk factors for AMD (the CFH and ARMS2 genotypes).
The presence of AMD was determined by grading retinal photographs. Multi-state models were used to model the relationship of current smoking and pack-years smoked and interactions with CFH and ARMS2 genes with the incidence and progression of AMD over the entire age range. The main outcome measurements were incidence and progression of AMD over the 20-year period and interactions between current smoking and pack-years smoked with CFH and ARMS2 genotype.
The researchers found that the incidence of early AMD over the 20-year period was 24.4%, and the incidence of late AMD was 4.5%. Current smoking was related to an increased risk of transitioning from minimal to moderate early AMD. A larger number of pack-years smoked was associated with an increased risk of transitioning from no AMD to minimal early AMD and from severe early AMD to late AMD. In addition, current smoking and a larger number of pack-years smoked were associated with an increased risk of death. The investigators found no evidence of interactions between current smoking or pack-years smoked and CFH or ARMS2 genotype.
The authors concluded that current smoking and a greater number of pack-years smoked increase the risk of the progression of AMD. Thy noted that their findings have important healthcare implications because smoking is a modifiable behavior.