The prevalence of macular degeneration may be decreasing in the United States! A study just released indicates that the rate of this blinding eye disease has decreased by about 15-20% compared to 20 years ago.
The results of the National Health and Nutrition Examination Survey (NHANES) included data collected from over 5500 individuals, age 40 and older. Each person received an eye examination including retinal photographs. Examiners looked for signs of geographic atrophy, exudative AMD, early AMD and advanced disease.
The NHANES study was performed between 2005-2008 and compared to the findings of a similar study completed from 1988-1994 (Third National Health and Nutrition Examination Survey).
The NHANES (2005-2008) analysis revealed a prevalence of AMD of 6.5% compared to the previous rate of 9.4% (1988-1994). There was a lower rate of macular degeneration found in blacks in both studies.
The authors conclude that the decrease in macular degeneration may be due to a decrease in smoking and changes in diet.
What Does This Mean?
The results of the survey are indeed encouraging and support the notion that smoking and diet may have some influence on the development of macular degeneration.
Keep in mind that the NHANES is a survey and not a longitudinal study. These were surveys that measured only the prevalence of a disease. This does NOT indicate the risk , or incidence, of developing macular degeneration.
The success of public health measures are difficult to assess and take large numbers of patients and years to assess. Smoking cessation and changes in diet are two examples of how our behavior may have changed over the past 20 years. It is possible that these habits have influenced the rate of developing macular degeneration.
On the other hand, it is possible that the methods of collecting the data are flawed, and thus, the analysis is biased, or, put simply, the conclusions are wrong. For instance, I am not sure if macular degeneration can be diagnosed in a patient 40 years old. Perhaps there was a bias towards too many 40 years olds in the recent study compared to the earlier study.
While different ethnic groups were studied in the recent survey, it is difficult to accurately compare this groups habits with each other and with the previous study.
On a positive note…perhaps we are doing something better! But in the meantime, make sure you get a regular eye exam.