December 16, 2016
By Anne Harding
NEW YORK (Reuters Health) - While people with hypertension are at increased risk of glaucoma, antihypertensive treatment is associated with a reduction of that extra risk, according to new findings.
While the findings don't yet warrant using blood pressure drugs to prevent or treat glaucoma, they should raise awareness of the increased glaucoma risk in people with hypertension, Dr. Anna Horwitz of the University of Copenhagen, who worked on the study, told Reuters Health by email.
"Based on the higher risk of glaucoma that we observe in hypertensive patients (even when controlling for age and gender), hypertensive patients could possibly be referred to ophthalmologists at a higher rate than currently - especially in relation to patients with a greater disposition for glaucoma, for example patients with a strong family history of glaucoma," she said.
While glaucoma has long been linked to blood pressure, the relationship is complex, Dr. Horwitz and her colleagues note in their report, online December 5 in Hypertension. Some studies show an association between high blood pressure and glaucoma and others show an increased risk in people with low blood pressure.
The team used regression discontinuity analysis, a statistical technique for gauging how treatments affect outcomes, to compare patients who were about to begin antihypertensive treatment to patients who had just started it. Using Danish registry data for a 16-year period, they identified more than 41,000 patients treated with glaucoma medication and antihypertensive drugs.
Among patients on antihypertensive drugs, the rate of glaucoma was 0.81 cases per 100 person years, compared to 0.19 cases per 100 person years in patients not treated with blood pressure medications.
The association remained after adjusting for age, sex and year-specific fixed effects. Among patients who initiated antihypertensive treatment, there was a 43% reduction in the pretreatment trend toward developing glaucoma.
Individual analyses found that all antihypertensive drugs, except vasodilators, were protective, with alpha-blockers and renin-angiotensin-system inhibitors seeming to have the strongest protective effect. The more antihypertensive medications a person was taking, the greater the protective effect.
"According to our knowledge, our study is the first to test for and find a causal effect of antihypertensive medication on glaucoma risk," Dr. Horwitz said. "Therefore, even though we used data for the complete Danish population over well more than a decade, we do not think our findings should currently form the basis for using anti-hypertensive medication in the treatment or prevention of glaucoma."
The next step, she added, will be for other researchers to attempt to replicate the findings. "In particular, it would be interesting to see if our findings can be confirmed in subsequent population-based studies and, even more importantly, in case-control studies," she said.
"If our finding of a preventive effect of hypertension on glaucoma is verified in subsequent research, it may imply that cardiologists and ophthalmologists should be jointly involved in the prevention or treatment of certain eye diseases," the researcher said.
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