MONDAY, June 14, 2010 (HealthDay News) -- A healthy diet helps guard against cataracts, while certain medications raise the risks of this common cause of vision loss, two new studies suggest.
And a third study finds that smoking increases the risk of age-related macular degeneration, another disease that robs people of their sight.
The first study found that women who eat foods that contain high levels of a variety of vitamins and minerals may be less likely to develop nuclear cataract, which is the most common type of age-related cataract in the United States.
The study is published in the June issue of the Archives of Ophthalmology.
The researchers looked at 1,808 women in Iowa, Oregon and Wisconsin who took part in a study about age-related eye disease. Overall, 736 (41 percent) of the women had either nuclear cataracts evident from lens photographs or reported having undergone cataract extraction.
"Results from this study indicate that healthy diets, which reflect adherence to the U.S. dietary guidelines . . . are more strongly related to the lower occurrence of nuclear cataracts than any other modifiable risk factor or protective factor studied in this sample of women," Julie A. Mares, of the University of Wisconsin, Madison, and colleagues said in a news release from the journal.
The second study found that medications that increase sensitivity to the sun -- including antidepressants, diuretics, antibiotics and the pain reliever naproxen sodium (commonly sold over-the-counter as Aleve) -- increase the risk of age-related cataract.
Researchers followed-up with 4,926 participants over a 15-year period and concluded that an interaction between sun-sensitizing medications and sunlight (ultraviolet-B) exposure was associated with the development of cortical cataract.
"The medications [active ingredients] represent a broad range of chemical compounds, and the specific mechanism for the interaction is unclear," Dr. Barbara E.K. Klein and colleagues at the University of Wisconsin, Madison, said in the news release. Their report was released online in advance of publication in the August print issue of the Archives of Ophthalmology.
Because the lens of the eye develops from the same tissue layer as the skin, sun-sensitizing medications may affect the eyes as well as the skin, the researchers explained.
"Our results need to be evaluated in other populations, especially in view of the increasing frequency of sun-sensitizing medications," they concluded. "If our findings are confirmed, it would be important to examine whether the effect is greater in those with higher levels of ambient sunlight (UV-B) exposure and if dose or duration of medication use is also important."
The third study, also published online and in the August print issue of Archives of Ophthalmology, found that smoking and cholesterol levels affect the risk for early-stage age-related macular degeneration (AMD).
AMD is uncommon before age 55 but the risk increases after that age, therefore most studies focus on AMD in middle-aged and older adults, according to background information in the report.
"To our knowledge, accurate estimates of prevalence of AMD among adults younger than 40 years are lacking. Such information is important for understanding the relationships of risk factors to AMD across the age spectrum and for identifying factors that might affect this disease earlier in life," Dr. Ronald Klein, of the University of Wisconsin, Madison, and colleagues said in the news release.
The study included 2,810 people, aged 21 to 84, who were assessed for the presence and severity of drusen. These yellow or white deposits in the retina are an early sign of AMD.
Overall, early AMD was detected in 3.4 percent of the participants, with rates ranging from 2.4 percent among those aged 21 to 34 to 9.8 percent for those aged 65 and older. Besides age, additional risk factors associated with increased risk for AMD included being male, heavy smoking for a long period of time, and being hearing impaired. Elevated levels of HDL ("good") cholesterol were associated with a lower risk for AMD, the study authors noted.
The findings "demonstrate that early AMD onset may occur in midlife. Some modifiable factors [smoking status and serum HDL cholesterol level] associated with AMD in older cohorts were associated with early AMD in this cohort of middle-aged adults," the researchers concluded.
The U.S. Centers for Disease Control and Prevention has more about common eye disorders.