The vision of millions of many Americans is in jeopardy, according to a new report by a leading national science board, which specifically cited growing rates of age-related macular degeneration (AMD) in its study of the rising toll of vision disease.
AMD is particularly on the rise, the authors note. Between 2000 and 2010, the number of U.S. adults aged 50 and older with advanced forms of AMD increased from 1.75 million to 2.07 million. By 2050 this number will more than double, to 5.44 million, according to National Institutes of Health statistics.
Who are most likely to be affected? Those most at risk are older, white, and female, the NASEM report states. In the U.S. population 50 years and older, women made up 65 percent of the nearly 2.1 million cases of late AMD in 2010.
Many of the factors that cause AMD cannot be prevented. Age is foremost among them. AMD is caused both by stressors inside the eye, such as drusen and poorly nourished cells; and also by stressors outside the eye, such as smoking and excessive exposure to sun. Over a lifetime, this damage accumulates and causes oxidative stress and subacute inflammation, both damaging to the eye. With age, the eye has a harder time protecting itself from these stressors, which explains why age itself is the biggest risk factor for AMD.
[To learn more about how aging affects our eyes and increases the risk for AMD, read a recent interview with MDR grantees working in this area.]
In addition to age, there are genetic susceptibilities to AMD that have been identified, but are not yet treatable. Individually, these small mutations and genetic abnormalities may not exert a great effect, but if more than one is present, or when combined with age and other risk factors, they could become influential. Research is showing that the genetic factors in AMD may work, in part, through a malfunctioning immune system. However, because these genetic factors have been spread across the genome, they are challenging targets for gene therapy.
On the plus side, NASEM cited research that is moving ahead to identify modifiable risk factors for AMD:
- Smoking is consistently identified as one of the top modifiable risk factors. Smoking around others poses a risk to their eyes and health, in addition to your own. Strength of evidence makes smoking cessation one of the best steps currently available to reduce one’s risk of AMD.
- Obesity also has been associated with AMD in some studies, although the reasons are not well understood and more research is needed. Conditions often linked with obesity, such as hypertension and hyperlipidemia, are also linked with AMD.
- Alcohol use and physical inactivity may play a role as risk factors for AMD, but again the evidence is not well established and research is needed here too.
- There may be synergistic effects among small groups of risk factors, such as obesity and alcohol, obesity and smoking, alcohol and high cholesterol, high cholesterol and smoking, and smoking and family history. Synergy makes the impact of a single risk factor (such as family history) stronger when combined with additional risk factors.
- Diet definitely plays a role in eye health , as we have seen in the AREDS study. Vitamins and minerals with antioxidant functions (eg, vitamins C and E, carotenoids [lutein, zeaxanthin, β-carotene], and zinc), and compounds with anti-inflammatory properties (omega-3 fatty acids, docosahexaenoic acid) are associated with a lower risk of AMD. [For more information about AREDS and eye-healthy vitamins and nutrients, read this Science News report.]
BrightFocus Foundation’s Macular Degeneration Research (MDR) program supports scientists worldwide who are investigating these and related topics.
The report encourages more federal funding for vision programs and research, as well as public-private partnerships to spread awareness. A coordinated outreach effort to reach at-risk groups is needed, NASEM recommends, and calls upon the nonprofit sector to join with federal authorities to spread awareness of vision health and risks. MDR research findings are frequently shared with both the public and scientific leaders around the globe.
The National Academies of Sciences, Engineering, and Medicine is an independent, nonprofit science advisory council signed into law by President Abraham Lincoln in 1863. Many of the nation’s top scientists, engineers, and health professionals volunteer their time to serve on key study panels.
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