Visual Impairment Rise Tied to Increased Diabetes Prevalence

Troy Brown

December 11, 2012

The prevalence of nonrefractive visual impairment in the United States has increased 21% overall and 40% among non-Hispanic whites aged 20 to 39 years, according to a study published in the December 12 issue of JAMA.

Fang Ko, MD, a third-year resident at the Wilmer Eye Institute, Dana Center for Preventive Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland, and colleagues analyzed data from 2 study periods of the National Health and Nutrition Examination Survey, a representative sample of the US population, in order "[t]o estimate prevalence of nonrefractive visual impairment and to describe its relationship with demographic and systemic risk factors including diagnosed diabetes."

In a telephone interview with Medscape Medical News, senior researcher David Friedman, MD, MPH, PhD, the Alfred Sommer Professor at the Wilmer Eye Institute and a professor in the Department of International Health at Johns Hopkins Bloomberg School of Public Health, explained, "One of the key findings of this study is that visual impairment is increasing in the United States.... [T]his is one of the first times we've shown that longer-duration diabetes is likely leading to visual outcomes that are going to affect not only older people who frequently have longer-term diabetes but a lot more young people as well."

Overall, diabetes prevalence increased from 6.5% (95% confidence interval [CI], 5.8% - 7.1%) in 1999-2002 to 8.2% (95% CI, 7.3% - 9.1%) in 2005-2008 (P = .001).

Nonrefractive visual impairment prevalence among adults in the United States was 1.4% (95% CI, 1.2% - 1.6%) in 1999-2002 and 1.7% (95% CI, 1.5% - 2.0%) in 2005-2008 (P = .03 for difference in prevalence).

Influence of Ethnicity

When considering age and ethnicity together, prevalence of nonrefractive visual impairment increased in most groups. This was statistically significant among white non-Hispanic participants aged 20 to 39 years (0.5% [95% CI, 0% - 0.9%] in 1999-2002 vs 0.7% [95% CI, 0.3% - 1.2%] in 2005-2008; P = .008) and among Mexican Americans aged 60 years or older (4.6% [95% CI, 2.7% - 6.6%] in 1999-2002 vs 8.9% [95% CI, 4.5% - 13.3%] in 2005-2008; P < .001).

For their multivariable logistic regression model, the researchers controlled for statistically significant risk factors that emerged from the univariable analysis including age, race/ethnicity, poverty, education, and health insurance status.

The passage of 10 or more years from the time of diabetes diagnosis was associated with an increased risk for nonrefractive visual impairment in the 2 periods (1999-2002: odds ratio, 1.93 [95% CI, 1.15 - 3.25]; 2005-2008: odds ratio, 2.67 [95% CI, 1.64 - 4.37]).

The most harmful factors that were significant in multivariable analyses, including lack of health insurance, lower education level, and poverty, remained stable or decreased in prevalence between the 2 periods studied. For this reason, the researchers stratified nonrefractive visual impairment by diabetes, the remaining risk factor.

In subgroup analysis by age and race/ethnicity, the prevalence of diabetes diagnosed at least 10 years ago increased significantly from 2.8% (95% CI, 2.4% - 3.2%) in 1999-2002 to 3.6% (95% CI, 3.0% - 4.2%) in 2005-2008 (P = .02). This increase between the earlier and later periods was found among all ethnicities and was significant among non-Hispanic blacks (4.3% [95% CI, 3.4% - 5.2%] vs 6.0% [95% CI, 4.9% - 7.1%]; P = .02) and Mexican Americans (2.3% [95% CI, 1.8% - 2.8%] vs 3.1% [95% CI, 2.5% - 3.8%]; P = .04).

This increase in prevalence continued after stratification by age and was statistically significant among participants aged 20 to 39 years (0.3% [95% CI, 0.1% - 0.5%] vs 0.7% [95% CI, 0.4% - 1.0%]; P = .03) and non-Hispanic whites aged 20 to 39 years (0.3% [95% CI, 0% - 0.5%] vs 0.7% [95% CI, 0.3% - 1.1%]; P < .001) in comparisons between 1999-2002 and 2005-2008, respectively.

"The visual acuity that we used for this study is worse than 20/40 in both eyes, which cannot be corrected with glasses. It's not blindness, but it is meaningful vision loss.... [T]hat kind of vision loss doubled among those 20-40 years of age," Dr. Friedman told Medscape Medical News.

A Plea for Prevention

"Virtually all permanent blindness from diabetes can be prevented with proper vision screening. The current [recommendation] of the American Academy of Ophthalmology, as well as many organizations, is to have an annual screening if you are an adult diabetic. People with diabetes need an eye exam every year so we can prevent permanent vision loss from it," Dr. Friedman explained.

In an accompanying editorial, David C. Musch, PhD, MPH, from the departments of Ophthalmology, Visual Sciences, and Epidemiology, and Thomas W. Gardner, MD, from the departments of Ophthalmology, Visual Sciences, and Molecular and Integrative Physiology at the University of Michigan in Ann Arbor, voice their concern about the increased prevalence in young adults.

In an email interview with Medscape Medical News Dr. Musch explained, "I hope that clinicians who routinely see children and adolescents in their practices will use these findings as another means to emphasize that obesity (and being overweight) is not a condition to ignore. A biological chain of events is activated in a person who is obese, and [nonrefractive visual impairment] is one potential and untoward outcome.

"Given the importance of vision to one's sense of health and well-being, and the potential for preventing obesity, diabetes and its complications by intervening early on via proper nutrition and exercise, cannot be overemphasized," Dr. Musch said.

"We know obesity is an important risk factor for diabetes, and we must learn from and support solid, evidence-based programs that aim to improve childhood nutrition and physical activity in schools, neighborhoods, and communities," he concluded.

The study was supported by the Centers for Disease Control and Prevention. The National Health and Nutrition Examination Survey is sponsored by the National Center for Health Statistics. Funding for the vision component was provided by the National Eye Institute. Dr. Friedman has reported having consulted for Alcon, Bausch & Lomb, Merck, Pfizer, Allergan, Nidek, and QLT. Full conflict-of-interest information is available on the journal's Web site. Dr. Musch has reported board membership with the American Academy of Ophthalmology Preferred Practice Pattern Committee and has received the Lew R. Wasserman merit award. Dr Gardner has reported receiving support from a physician-scientist award. Dr. Musch and Dr. Gardner also both received awards to support their research from Research to Prevent Blindness.

JAMA. 2012;308(22):2361-2368, 2403-2404. Abstract