Obstructive Sleep Apnea is an Independent Risk Factor for Non-Arteritic Ischemic Optic Neuropathy

Abstract

Purpose: : To determine whether obstructive sleep apnea (OSA) is a risk factor for non-arteritic ischemic optic neuropathy (NAION) by measuring objective parameters of OSA in NAION subjects and non-NAION controls, taking into account confounding risk factors.

Methods: : Thirty-two subjects were recruited from the VMR Institute and the Doheny Eye Institute neuro-ophthalmology clinic. There were 24 NAION patients (16 males, 8 females, mean age = 60.3 years) and 8 controls (2 males, 6 females, mean age 51.9 years). Using the Apnea Risk Evaluation System Unicorder (ARES, Advanced Brain Monitoring, Inc, Carlsbad, CA) subjects acquired 2-3 nights of sleep study data at home. An apnea-hypopnea index (AHI) with 4% desaturation (AHI-4% = the average number of obstructive breathing events associated with 4% oxygen desaturation per hour) and an AHI with 1% desaturation (AHI-1%) was calculated for each patient using the formula: AHI = Number of Abnormal Breathing Events / [Total Recording Time - (Actigraphically Awake Time + Invalid Signal Time)]. AHI-4% scores of 5-14 were defined as mild OSA, and AHI-4% scores ≥ 15 were defined as moderate OSA.

Results: : Using AHI-4%, 14/24 (59%) NAION patients had mild to moderate OSA. Of the non-NAION controls, only 1/8 (13%) had mild to moderate OSA. Using AHI-1%, 14/24 (58%) NAION patients had AHI ≥ 15, as compared to 0/8 (0%) non-NAION controls with an AHI ≥ 15. The average AHI-4% (± SEM) for NAION patients was 5-fold higher (8.8 ± 1.8) than for non-NAION controls (1.8 ± 0.75; P = 0.0065). Similarly, the average AHI-1% for NAION patients (18.9 ± 2.3) was greater than for controls (7.6 ± 1.7; P=0.006). Subgroup analysis of subjects without diabetes or hypertension [NAION (n=12) & non-NAION (n=5)] found an AHI-4% (± SEM) for NAION patients of 8.2 (± 2.7), which was significantly greater than non-NAION controls (AHI-4% =1.6 ± 1.1; P=0.026).

Conclusions: : There is an increased prevalence of OSA in NAION. Even after accounting for the confounders of diabetes and hypertension by subgroup analysis, there was an independent association of OSA with NAION.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • neuro-ophthalmology: optic nerve