November 24, 2017
By Anne Harding
NEW YORK (Reuters Health) - The risk of age-related macular degeneration (AMD) in the U.S. declined sharply across generations during the 20th century, new findings show.
“There’s some hope for current Baby Boomers that as they age they may be able to live longer with better vision than their parents did,” Dr. Karen J. Cruickshanks of the University of Wisconsin-Madison, who helped conduct the study, told Reuters Health by phone. “This dramatic decline suggests that there are a lot of modifiable risk factors that we haven’t yet identified, that we might do better at preventing AMD.”
Cardiovascular disease, dementias and other aging-related conditions, including AMD, have declined over time among people born in the first half of the 20th century, Dr. Cruickshanks and her team note in JAMA Ophthalmology, online November 16.
To investigate whether the decline in AMD continued in Baby Boomers, they looked at data from the Beaver Dam Eye Study (BDES) and the Beaver Dam Offspring Study (BOSS), which include residents of the Wisconsin city who were aged 43-84 years in 1987-1988 and their children.
The analysis included 2,746 people from BDES and 2,073 of their offspring, all of whom were free of AMD at baseline and were classified into generational groups: the Greatest Generation (857 study participants born 1901-1924), the Silent Generation (2,068, born 1925-1945), the Baby Boom Generation (1,424, born 1946-1964) and Generation X (470, born 1965-1984).
Five-year AMD incidence was 4.2% overall and increased with age. Age- and sex-adjusted five-year AMD incidence was 8.8% for the Greatest Generation, 3% for the Silent Generation, 1% for Baby Boomers, and 0.3% for Generation X. Adjusted AMD risk declined by more than 65% with each generation.
When the researchers took other AMD risk factors into account, such as smoking, education, exercise, and medication use, the generational plunge in risk declined slightly, but remained significant at 60%.
The reasons behind the decline in AMD risk remain “a mystery,” according to Dr. Cruickshanks. “People have suggested that it may have something to do with improvements in air and water quality, nutrition, medical care for childhood disorders, better maternal and child health,” she said. “There’s something we haven’t yet discovered that’s contributing to retinal health.”
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The researcher added, “So often our stories are about, ‘here’s something horrible that’s going to happen,’ but this is an opportunity to say that not only are we living longer, but we look like we’re living healthier.”
The current findings, along with those showing similar benefits in other types of aging-related illness, are “great news” in terms of older people being able to live independently for longer and avoiding disability, she said.
Dr. Cruickshanks and her team are continuing to follow the BDES and BOSS cohorts. “It’s always possible that the trend may flatten out or even change,” she said, noting that Baby Boomers are heavier than previous generations, which could increase their risk.
Physicians should “remind people that that smoking cessation, weight control, exercise, high-blood pressure control, all of the things that are important for eye health in general, are still important,” the researcher said. “Even though we’re seeing people’s risk is declining, we still want to encourage good, healthy habits.”
In a commentary accompanying the study, Dr. Raphael Goldacre of the University of Oxford in the UK and Dr. Tiarnan Keenan of the U.S. National Institutes of Health in Bethesda note, “From a health care provision point of view, if a decline in AMD across recent generations is real, it needs to be considered in the context of an aging population.”
The world’s population of people with late AMD is expected to double to 18.6 million by 2040, they point out.
“By this time, more than half of the late AMD cases worldwide will occur in Asia, including China, suggesting that AMD should no longer be considered primarily a disease of European descended populations,” the editorialists conclude. “Determining the causes of any apparent decline across the generations in age-specific incidence of AMD will be vital in seeking to offset the effect of aging populations in these regions.”
SOURCES: http://bit.ly/2B5Wawj and http://bit.ly/2mYOoCc
JAMA Ophthalmol 2017.
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