Antihypertensives May Cut Glaucoma Risk

Antihypertensive Medication Postpones the Onset of Glaucoma: Evidence From a Nationwide Study

Horwitz A, Klemp M, Jeppesen J, Tsai JC, Torp-Pedersen C, Kolko M
Hypertension. 2017;69:202-210

Study Summary

To assess whether there is any association between the use of antihypertensive medication and the development of glaucoma, researchers looked at data from more than 2.6 million people from 40 to 95 years of age collected between the years 1996 and 2012 by the National Danish Registry of Medicinal Products Statistics. From this group, 739,494 patients were treated with antihypertensive drugs, and 115,617 were shown to have incident glaucoma.

The mean age at hypertension onset was 60.3 years. Among individuals treated with antihypertensive medication, 5.8% initiated treatment with glaucoma medication throughout the study period. In comparison, 1.3% of patients without hypertension were prescribed glaucoma medication within the period. Furthermore, 32.1% of patients with glaucoma were prescribed antihypertensive medication within the period. The rate of glaucoma is 0.81 cases per 100 person-years in individuals treated with antihypertensive drugs, which is substantially larger than the corresponding rate of 0.19 cases per 100 person-years in individuals not treated with antihypertensive drugs.

In summary, the analysis confirms that there is a correlation between hypertension and glaucoma, although the treatment of hypertension with any antihypertensive medication (except vasodilators) may protect against glaucoma.

Viewpoint

Studying how the use of antihypertensives affects the development of glaucoma is complex, as it relies on retrospectively analyzing data from trends and regression analysis instead of a direct head-to-head comparison in the form of a prospective study. Such a study would not be feasible or ethical, as it would require withholding antihypertensive medications to patients with documented hypertension. Nonetheless, this study did determine that there is a positive trend in the development of glaucoma over time and a negative causal effect of antihypertensive drugs on the risk for glaucoma. The size of the effect is substantial, with the analysis indicating that antihypertensive treatment reduces the risk of developing glaucoma by around 43% of the pretreatment trend.

Although these data seem very promising, a few basic limitations must be considered.

First, despite thousands of participants, the Danish population is likely very ethnically homogeneous, and the results may not be applicable to other diverse populations. African American and Hispanic individuals have a higher risk for both hypertension and glaucoma than the white population. Furthermore, the onset of hypertension is earlier in the African American population,^[1] which may alter the correlating onset of glaucoma.

Second, the Danish registry only provides information on prescriptions, and it was not possible to define the type of glaucoma or even confirm the actual diagnosis. The glaucoma subset that was postponed in these patients could have consisted of neovascular glaucoma (NVG) resulting from a central retinal vein occlusion (CRVO). The risk for a CRVO increases with hypertension^[2]; thus, controlling hypertension may decrease the risk for NVG but not for the most common subtype of primary open-angle glaucoma.

Third, because the study did not define the type of glaucoma or confirm its diagnosis, it is difficult to conclude that the actual onset of disease is postponed with antihypertensive treatment. It is possible that antihypertensive use did not postpone the onset of glaucoma but instead just the onset of glaucoma treatment. Patients on antihypertensives (eg, beta blockers) will also have some reduction in intraocular pressure (IOP). Therefore, some patients who are considered glaucoma suspects may be observed longer without treatment if the pressure is within normal limits due to the IOP-lowering properties of systemic beta blockers.^[3] In contrast, if the same patients have higher IOPs because they are not being treated with systemic beta blockers, they may be started on topical treatment sooner. Similarly, patients with ocular hypertension may not be getting treated topically if the IOP is reduced with systemic treatment, whereas patients not on systemic treatments may be more likely to get treatment. This is indeed consistent with the conclusion that antihypertensive medication use may delay the onset of treatment but may not conclusively support the assumption that there is delay in onset of the actual disease.

Although this study involves a large population and complex statistics to analyze the large database of information, it may be difficult to conclude that antihypertensive medication delays the onset of glaucoma. It can be said that it delays the onset of therapy, which may or may not correlate to the onset of disease. It also cannot define which subsets of glaucoma may be postponed by starting antihypertensive medication. However, this study did demonstrate the increased incidence of glaucoma in patients with hypertension. Therefore, it is important for clinicians to screen patients with higher risk factors and to be aware of this correlation to ensure proper patient care.

Abstract

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