American Journal of Epidemiology ª The Author 2009. Published by the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail:
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Vol. 169, No. 7 DOI: 10.1093/aje/kwn393 Advance Access publication February 20, 2009
Original Contribution Red Meat and Chicken Consumption and Its Association With Age-related Macular Degeneration
Elaine W.-T. Chong, Julie A. Simpson, Luibov D. Robman, Allison M. Hodge, Khin Zaw Aung, Dallas R. English, Graham G. Giles, and Robyn H. Guymer Initially submitted February 7, 2008; accepted for publication November 25, 2008.
diet; macular degeneration; meat; poultry
Abbreviations: AMD, age-related macular degeneration; CI, confidence interval; FFQ, food frequency questionnaire.
Age-related macular degeneration (AMD) is the leading cause of severe vision loss in people aged 50 years or older in the developed world (1, 2). Early AMD is characterized clinically by yellow deposits known as drusen and alterations in retinal pigmentation. These are thought to indicate an unhealthy retina which predisposes to late visually threatening complications, or late AMD (3). Late AMD develops when there is ingrowth of new blood vessels that bleed into the subretinal space (exudative or ‘‘wet’’ type) or when the macula atrophies (geographic atrophy or ‘‘dry’’ type). This progressive late-onset degenerative disease affects central vision, which is essential for independent activities of daily living. The loss of central vision not only results in a significant loss of quality of life but also places a massive burden on health-care resources (4, 5). With the aging US population, it is estimated that by 2020 the number of Americans with late AMD will increase by 50% to 3 million (1).
A similar doubling of AMD prevalence in Australia, with direct costs to the community reaching over A$1 billion by the year 2020, is also expected (4). Risk factors for AMD include age, family history, and smoking, with smoking being the only modifiable risk factor consistently found (6). To date, the pathogenesis of AMD remains unknown; and with treatment available only for neovascular complications of AMD (7), the identification of modifiable risk factors has enormous public health implications. Meat consumption has been associated with AMD in several studies primarily evaluating fat intake and AMD (8–10); despite this association, thus far no study has focused specifically on meat intake or evaluated this association in detail. High meat intake has been associated with higher levels of N-nitroso compounds (11), heme iron (12), and advanced glycation end products (13), which could result in oxidative damage and could be toxic to the retina;
Correspondence to Dr. Elaine Chong, Centre for Eye Research Australia, University of Melbourne, 32 Gisborne Street, East Melbourne 3002, Victoria, Australia (e-mail:
[email protected]).
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Am J Epidemiol 2009;169:867–876
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Age-related macular degeneration (AMD) is the leading cause of blindness among older people, and diet has been postulated to alter risk of AMD. To evaluate associations between red meat and chicken intake and AMD, the authors conducted a cohort study of 6,734 persons aged 58–69 years in 1990–1994 in Melbourne, Australia. Meat intake was estimated from a food frequency questionnaire at baseline. At follow-up (2003–2006), bilateral digital macular photographs were taken and evaluated for AMD (1,680 cases of early AMD, 77 cases of late AMD). Logistic regression was used to estimate odds ratios, adjusted for age, smoking, and other potential confounders. Higher red meat intake was positively associated with early AMD; the odds ratio for consumption of red meat 10 times/week versus
