Findings from a recent study published in the Journal of Glaucoma assessed cognitive impairment (CI) in individuals with primary open-angle glaucoma (POAG).
Give me some background.
Glaucoma is considered to be a part of a continuum of neurodegenerative disorders.
In fact: Widespread changes in the gray and white matter of the cerebral cortex (including the visual pathways) have been observed using magnetic resonance imaging (MRI).
Previous studies have demonstrated that glaucoma patients tend to have reduced cognition compared to healthy individuals with similar values reported in the literature for patients with mild Alzheimer’s disease (AD).
Bring in serum cortisol levels.
Raised serum cortisol level is another common trait between patients with glaucoma and CI, the study authors highlighted.
Of note, raised cortisol levels have been associated with:
- An increase in intraocular pressure (IOP) due to changes in the trabecular meshwork
- Memory decline
- Increased evidence of cognitive deficits due to the adverse effect of cortisol on the hippocampal neurons
As such: A research team sought to assess cognitive function in glaucoma patients (and healthy controls) to determine if CI:
- Goes undetected in glaucoma patients
- Contributes to poor quality of life
- Impacts performance on visual function tests and medication adherence
Now talk about the study.
In this cross-sectional case-control study, investigators compared individuals aged 40+ with POAG (cases, n=70) to age- and sex-matched healthy individuals (controls, n=70) who presented to a tertiary care center in North India.
Detailed ophthalmological evaluations, cognitive assessments, and serum cortisol levels were analyzed to determine CI.
Various domains of cognitive function were comprehensively assessed using the following tests:
- Addenbrooke Cognitive Examination (ACE-III)
- Attention/orientation, memory, language, verbal fluency, and visuospatial skills
- Post Graduate Institute Memory Scale (PGIMS)
- Verbal and nonverbal memory
- Wisconsin Card Sorting Test (WCST)
- Nonverbal executive functions
- Go No-Go Task (GNG)
- Inhibitory control
- Trail Making Test (TMT)
- Attention and working memory
Findings?
Compared to controls, patients with POAG had (not surprisingly) significantly:
- Higher intraocular pressure (IOP) and cup-disc ratio (p<0.001)
- Lower retinal nerve fiber layer (RNFL) thickness and mean deviation
Further: POAG patients had significantly lower scores on ACE-III and PGIMS (p<0.001) and longer test completion time in TMT-A (P=0.001).
What else?
The performance of POAG patients was significantly worse on most parameters of the WCST and GNG tasks.
In addition: To ensure reliable findings, the central visual acuity in both groups was comparable—minimizing the role of visual impairment as a confounding factor.
What about serum cortisol levels?
Serum cortisol level was significantly higher in POAG patients (11.75 mcg/dl) compared to controls (7.93 mcg/dl, p=0.02).
A significant correlation was observed between serum cortisol levels and:
- WCST correct response (p=0.04)
- WCST error response (p=0.002)
- Total time taken in TMT-A (p=0.03)
Visual field (VF) mean deviation also exhibited a significant correlation with serum cortisol level (p<0.001) and total time taken on WCST (p=0.03) and TMT-A (p=0.03).
Expert opinion?
The clinical significance of this study primarily involves vigilance for early CI signs in glaucoma patients—particularly as they age.
“If a patient frequently reports missing medications or exhibits signs of non-compliance such as inadequate prescription refills, fluctuating IOP, or disease progression, considering CI is imperative,” the study authors emphasized.
Recommended interventions for CI: Mindfulness meditation has been shown to reduce serum cortisol levels, increase white matter, improve cognition, and reduce IOP.
Limitations?
These included:
- Additional factors shown to be individually associated with or can impact CI (ex., smoking, obesity, use of glaucoma medications, etc.) were not evaluated
- The highest level of education and socioeconomic status was not recorded for the study participants
Take home.
These findings suggest that individuals with POAG exhibited higher CI and raised serum cortisol levels than age-matched healthy controls.
As such: Early recognition and management of CI are pivotal for enhancing patient quality of life and implementing comprehensive glaucoma care.
- Further: Lifestyle changes with relaxation techniques to reduce stress, such as meditation, may be helpful in arresting neurocognitive decline and need to be explored for reversing CI in glaucoma patients.