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. Author manuscript; available in PMC: 2017 Mar 1.
Published in final edited form as: JAMA Ophthalmol. 2016 Mar;134(3):294–303. doi: 10.1001/jamaophthalmol.2015.5601

Table 3. Age-adjusted and multivariable adjusted relative risk (95% confidence interval) of subtypes of primary open-angle glaucoma, by quintiles of nitrate intake,* in Nurses' Health Study (1984-2012) and in Health Professionals' Follow-up Study (1986-2012).

Quintiles of dietary nitrate intake
SUBTYPES DEFINED BY INTRAOCULAR PRESSURE† Q1 Q2 Q3 Q4 Q5 p-trend p-heterogeneity
High-tension glaucoma (intraocular pressure ≥ 22 mm Hg; n=998) Women Cases 133 117 138 121 142 0.75
Multivariable RR(95% CI)‡ 1.00 (ref) 0.83 (0.64, 1.06) 0.89 (0.70, 1.14) 0.75 (0.58, 0.96) 0.87 (0.68, 1.11) 0.29
Men Cases 68 62 75 82 59
Multivariable RR (95% CI)‡ 1.00 (ref) 0.89 (0.62, 1.27) 1.01 (0.72, 1.43) 1.11 (0.79, 1.56) 0.73 (0.51, 1.06) 0.20
Pooled§ Multivariable RR (95% CI) 1.00 (ref) 0.85 (0.69, 1.04) 0.93 (0.76, 1.13) 0.90 (0.61, 1.32) 0.82 (0.67, 1.01) 0.11
Normal-tension glaucoma (intraocular pressure < 22 mm Hg; n=487) Women Cases 77 56 69 78 69
Multivariable RR(95% CI)‡ 1.00 (ref) 0.68 (0.48, 0.96) 0.77 (0.55, 1.07) 0.82 (0.59, 1.13) 0.71 (0.51, 1.00) 0.22
Men Cases 30 27 26 29 25
Multivariable RR (95% CI)‡ 1.00 (ref) 0.90 (0.52, 1.56) 0.84 (0.48, 1.47) 0.98 (0.57, 1.70) 0.72 (0.41, 1.28) 0.34
Pooled§ Multivariable RR (95% CI) 1.00 (ref) 0.73 (0.55, 0.98) 0.79 (0.59, 1.05) 0.86 (0.65, 1.13) 0.71 (0.53, 0.96) 0.12
SUBTYPES DEFINED BY INITIAL VISUAL FIELD LOSS PATTERN‖
POAG with peripheral visual field loss only (n=836 cases) Women Cases 120 91 121 120 124 0.01
Multivariable RR(95% CI)‡ 1.00 (ref) 0.71 (0.54, 0.93) 0.86 (0.67, 1.12) 0.83 (0.64, 1.07) 0.84 (0.65, 1.09) 0.60
Men Cases 47 47 58 62 45
Multivariable RR (95% CI)‡ 1.00 (ref) 1.01 (0.67, 1.55) 1.20 (0.80, 1.80) 1.29 (0.86, 1.92) 0.87 (0.57, 1.34) 0.67
Pooled§ Multivariable RR (95% CI) 1.00 (ref) 0.82 (0.58, 1.15) 0.98 (0.72, 1.34) 1.00 (0.65, 1.54) 0.85 (0.68, 1.06) 0.50
POAG with early paracentral visual field loss (n=433 cases) Women Cases 61 64 58 56 49
Multivariable RR (95% CI)‡ 1.00 (ref) 0.95 (0.66, 1.35) 0.79 (0.55, 1.14) 0.74 (0.51, 1.07) 0.64 (0.43, 0.94) 0.01
Men Cases 35 28 28 32 22
Multivariable RR (95% CI)‡ 1.00 (ref) 0.79 (0.47, 1.34) 0.72 (0.42, 1.22) 0.84 (0.50, 1.39) 0.44 (0.25, 0.78) 0.01
Pooled§ Multivariable RR (95% CI) 1.00 (ref) 0.89 (0.67, 1.20) 0.77 (0.57, 1.04) 0.77 (0.57, 1.04) 0.56 (0.40, 0.79) 0.0003

Abbreviations: RR = Relative Risk; CI = Confidence Interval; IOP=intraocular pressure; VF=visual field

*

Intake calculated using cumulative average (i.e., average of all available intake data from food frequency questionnaires completed before each two-year period at risk).

†

Based on the maximum untreated intraocular pressure at diagnosis.

‡

All multivariable analyses were adjusted for the same variables as in Model 1 in Table 2.

§

Pooled results were calculated using Dersimonian and Laird methods with random effects.

‖

Based on visual field (VF) loss pattern as of the earliest reliable VF at diagnosis that was reproduced at the latest reliable VF. Cases (n=216) with advanced VF loss at diagnosis who could not be categorized based on initial presenting VF loss as either peripheral VF loss only or early paracentral VF loss were censored during analyses. See Methods for how cases were categorized according to initial presenting VF loss.

For testing whether the associations between nitrate and one POAG subtype is significantly different from that with another subtype, we combined the two datasets into one, then conducted Cox regression analyses that stratified on the 2 cohorts, which allowed for the baseline hazard function to be different in the cohorts; we then used the Lunn-McNeil approach59 to test for heterogeneity in associations and derived p for heterogeneity.