Blood Pressure Meds May Up AMD Risk, 20-Year Study Suggests

Larry Hand

June 04, 2014

Use of vasodilators to control blood pressure may be associated with an increased risk for early development of age-related macular degeneration (AMD), according to an article published online April 30 in Ophthalmology.

However, further research is needed before any recommendations are made to change medication prescriptions, according to the researchers.

Ronald Klein, MD, MPH, from the Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, and colleagues conducted a population-based longitudinal study of residents of Beaver Dam, Wisconsin, during a 20-year period beginning in 1988.

The residents, aged 43 to 86 years, enrolled in the Beaver Dam Eye Study, a National Eye Institute–funded study of age-related eye diseases, and have had eye examinations every 5 years through 2008-2010. Of the 4926 participants at baseline, 1913 remained in the study for a 20-year follow-up; 99% of the participants are white.

The overall 5-year incidence of early AMD during the 20-year period came to 8.4%, or 592 cases in 7012 person-visits, compared with 1.4% (128 cases/9133 visits) for late AMD.

Participants taking vasodilators had a 72% higher risk of developing early AMD (95% confidence interval [CI], 1.25 - 2.38) after adjustments for age and sex. The excess risk was even higher, at 81%, among individuals using oral nitroglycerin (95% CI, 1.14 - 2.90). In addition, the researchers calculated that persons taking oral beta blockers were 71% more likely to develop exudative AMD (95% CI, 1.04 - 2.82).

"With increasing use of vasodilators in an aging population, it is important to examine further this potential association. The findings from our study need additional replication to be confirmed [possibly in clinical trials]," the researchers note.

Mechanism Unknown

The researchers add that the mechanism for such an association is unknown but may, according to a 1995 study, be related to stiffening of blood vessels that occurs during AMD. They also write that they were not able during this analysis to distinguish whether the association they found was for blood pressure medicines or blood pressure itself.

"The mechanism [may have] to do with the effect of the drugs on blood flow in the chorioid of the eye, the layer [of vessels and connective tissue] beneath the retina," Dr. Klein told Medscape Medical News. Studies have shown inconsistent relationships between the use of vasodilators and AMD, he added.

"I wouldn't say there's a final take-home message, except not to change their medications because the findings may be by chance, they've not been replicated, and there may be bias of indication. The drugs being used may not be separated from the hypertension itself. We were unable to separate the two," he said.

Aging and Increased Medications Hard to Tease Apart

"The next step is for further epidemiological studies to replicate the results and find a consistent relationship, and then the ultimate that might be done is a clinical trial," he said. "The likelihood of such a trial occurring is low, so we're left with somewhat of a dilemma of separating out the condition itself or the drug," he added.

Matthew J. Welch, MD, an ophthalmologist in private practice with Retina Specialists of Southern Arizona, in Tucson, formerly with Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, agrees.

"The best thing that could be done is a randomized controlled study," he told Medscape Medical News. However, "[i]t would be quite an overhaul because you'd have to follow these people for a long, long time. The charged task is not insignificant. I think it would be hard to have a control group, because so many folks have blood pressure-related issues."

Blood pressure medicine "has kind of become as ubiquitous as table salt," he added. "A problem with macular degeneration in general is that we know that age alone keeps on increasing your risk, and as we age we start taking more medications. Macular degeneration is such a heterogeneous disease. Even for a particular individual, it can be so different between 2 eyes. That makes it additionally hard to make really broad-reaching conclusions."

AMD is the leading cause of vision loss and blindness among Americans aged 65 years old and older. Previous research pegged the incidence of AMD at 9.1 million cases in 2010 and projected that number to grow to up to 17.8 million cases in 2050, depending on how new therapies might mitigate the trend.

This research was supported by the National Eye Institute. The authors and Dr. Welch have disclosed no relevant financial relationships.

Ophthalmology. Published online April 30, 2014. Abstract

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