1. In a cohort of about 500 eyes with primary open-angle glaucoma (POAG), higher smoking intensity in pack-years was significantly associated with faster worsening on visual field (VF) testing.
2. Baseline 20 pack-year or greater smoking history was associated with higher risk of VF progression over a median 12.5 years of follow-up, though mild and moderate smoking history were not.
Evidence Rating Level: 2 (Good)
Study Rundown: Despite the prevalence of glaucoma and the known contribution of smoking to many chronic diseases, the role of smoking as a risk factor for glaucoma onset and progression remains unclear. This multicenter retrospective cohort study aimed to show a clinical relationship between smoking and progression of primary open-angle glaucoma (POAG). More than 500 eyes of about 350 patients with POAG were followed using visual field (VF) testing for a median of 12.5 years. Subjects with any smoking history did not have significantly different rates of VF worsening than those with none. However, smoking intensity in pack-years was significantly associated with faster VF worsening over the study duration. In multivariable models adjusted for age, body mass index (BMI), and baseline ocular characteristics including intraocular pressure (IOP), patients who had a heavy smoking history of 20 pack-years or more at baseline were 74% more likely to progress based on VFs over the study period than those who had never smoked. Mild and moderate smoking history were not associated with increased risk. This is one of the first high-quality studies to show a positive association between smoking and clinical glaucoma progression. Analysis included only cumulative smoking history at baseline, rather than current smoking intensity or cessation status, which limits the applicability of the findings in advising patients who do have a smoking history. Though several mechanisms have been proposed for the harmful effects of tobacco use on eyes with POAG, including increased oxidative stress and microvascular blood flow changes, further study is required in order to shed light on possible therapeutic pathways.
Relevant Reading: Risk factors for glaucoma onset and progression
In-Depth [retrospective cohort]: Patients enrolled in two cohort studies across four medical centers were included. Patients received annual ophthalmologic exams. VFs were assessed using the Humphrey field analyzer. Smoking history and intensity in pack-years were self-reported; 42.1% of patients had ever smoked and 11.0% were defined as heavy smokers based on greater than 20-pack years’ history. Patients with at least three years of follow-up and at least five VFs were included. Patients with more than 33% false-negative or false-positive errors on VF testing were excluded. Glaucoma severity was classified as early or moderate based on mean deviation (MD) on 24-2 VFs. Multivariable models adjusted for IOP, central corneal thickness, and baseline MD. Each 10 pack-years smoking was associated with a 0.05 dB decrease per year in MD (95% confidence interval -0.08 to -0.01 dB/year). Kaplan-Meier survival analysis was also performed to compare rates of progression, defined as significant negative change in MD for at least two visits, between heavy smokers and never smokers.
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