Background: Previous studies have reported that vascular disease is associated with glaucoma. However, the relationship between blood pressure (BP) and glaucoma has been inconsistent. We investigated whether there is a nonlinear association between BP and glaucoma in an adult population of the United States.

Methods: From the 2005-2008 National Health and Nutrition Examination Survey data, 4,137 participants aged 40 years and older were chosen. BP was assessed based on a standard protocol. Glaucoma was determined using fundus photographs. Age, sex, race/ethnicity, education, poverty, antihypertensive medication, and history of cardiovascular disease were also considered in analyses.

Results: The prevalence of glaucoma was 1.2%. In the multivariate analysis, both high (≥161 mm Hg) and low (≤110 mm Hg) levels of systolic BP were found to be positively associated with glaucoma in those without antihypertensive medications: their prevalence ratios (95% confidence intervals) for glaucoma were 6.42 (1.01-40.81) and 5.46 (1.77-16.53), respectively, when compared to the reference levels of systolic BP (111-120 mm Hg). Also, both high (≥91 mm Hg) and low (≤60 mm Hg) levels of diastolic BP were positively associated with glaucoma in those without antihypertensive medications. The prevalence of glaucoma was lowest in those having systolic BP levels of 111-120 mm Hg and diastolic BP levels of 81-90 mm Hg. However, there were no such U-shaped relationships in those with antihypertensive medications.

Conclusions: There was a nonlinear (U-shaped) relationship between BP and the glaucoma in those without antihypertensive medications. Future longitudinal studies are warranted to confirm our findings, including the optimal BP levels for the prevention of glaucoma.