Findings from a recent study published in the Journal of Glaucoma assessed the relationship between intraocular pressure (IOP) and the risk of obstructive sleep apnea (OSA).
Give me some background.
Previous studies have demonstrated a link between glaucoma and OSA, with one finding that an intermediate or high risk of OSA was associated with 50% higher odds of having glaucoma.
OSA is characterized by the complete or partial obstruction of the upper airway during sleep, leading to recurrent hypoxia and downstream effects such as:
- Oxidative stress
- Systemic and vascular inflammation
- Endothelial dysfunction
These mechanisms result in changes to ocular tissues, including decreased ocular perfusion pressure (OPP) and oxygen supply to the optic nerve—eventually leading to glaucomatous optic neuropathy.
Bring it back to the study.
With this association in mind, a Korean research team hypothesized that there would also be an association between a higher STOP-BANG score—which is a questionnaire that screens for OSA—and elevated IOP.
Now talk about the study.
In this population-based, cross-sectional study, investigators included 6,315 Korean adults (aged 40+) from the Korea National Health and Nutrition Examination Survey (KNHANES) VIII database who were recruited between 2019-2021.
- About this survey: The KNHANES was created by the Korean Disease Control and Prevention Agency (KDCA) to evaluate the health and nutritional status of the Korean population for health policy development.
The risk of OSA was measured by STOP-BANG questionnaire, and IOP levels were measured using rebound tonometry.
Findings?
Participants with a STOP-BANG score of 3-8 had an adjusted odds ratio (AOR) of 1.27 (95% confidence interval [CI] 1.12-1.43) compared to those with a score of 0-2.
- Meaning: There was a 27% increase in the odds of patients having high IOP.
Further: Subjects had a 24-40% higher chance of elevated IOP with the following characteristics (compared to those without):
- Loud snoring
- Observed breathing interruptions during sleep
- Hypertension
- Wide neck circumference
The OR for high IOP in the group with all four of the above-mentioned factors was 2.09 times higher (95% CI 1.26-3.46) than in the group without these factors.
- Meaning: There was a 209% increase in the odds of patients having high IOP.
Expert opinion?
The study authors noted that from a public health perspective, these findings indicate the need for IOP measurement in patients with high STOP-BANG scores.
In addition: They explained that neck circumference—an index of upper body obesity—was used instead of body mass index (BMI) as a risk parameter for IOP measurements because it positively correlates with changes in systolic and diastolic blood pressure.
- Of note: BMI does not account for muscle mass, fat distribution, or other individual differences in body shape.
Keep going…
Obesity-related fat deposition in the neck can narrow the pharyngeal lumen, causing it to obstruct when sleeping and potentially causing venous engorgement.
Consequently: An increase in episcleral venous pressure, which leads to reduced aqueous outflow, is associated with high IOP.
Limitations?
These included:
- The ability to detect causal relationships between the risk of OSA using the STOP-BANG score and IOP was limited
- Several other ocular features (such as central corneal thickness and angle status) were not considered in addition to IOP level because they were not collected in the KNHANES
- As a result, investigators measured the IOP in both eyes of participants six times and an average was calculated from these values
- Due to the homogenous nature of the study population (i.e., Korean participants aged 40+), these findings may not be generalizable
Take home.
These findings suggest that a higher STOP-BANG score was associated with an increased risk of high IOP in Koreas aged 40+.
Among the STOP-BANG components, the characteristics listed below were individually and in combination associated with high IOP:
- Loud snoring
- Observed breathing interruptions during sleep
- Hypertension
- Wide neck circumference