Normal-tension glaucoma linked to cognitive impairment
Study results showed an association between normal-tension glaucoma and dementia-related cognitive impairment.
Based on previous but limited studies, Sean Mullany, MD, from Flinders University in Australia, and colleagues designed a cross-sectional comparison of cognition in older patients with either normal-tension glaucoma (NTG) or high-tension glaucoma (HTG).
The study comprised 248 patients with NTG and 349 patients with HTG, matched for age (65 years or older) and sex.
Mullany and colleagues said it is unclear whether the impaired cognition among study participants was due to Alzheimer’s disease or alternative dementia syndromes.
“Common dementia phenotypes are known to be difficult to distinguish clinically, as their cognitive manifestations are variable, and they commonly coexist in patients with dementia,” they wrote.
Multivariate analysis adjusted for age, sex and ethnicity showed that NTG status correlated with a higher prevalence for impaired cognition compared with HTG status (OR = 2.2; 95% CI, 1.1-6.7).
Another analysis performed to investigate confounding factors such as history of stroke, smoking, hypertension and diabetes showed a persisting association between NTG status and cognitive impairment (OR = 2.6; 95% CI, 1.1-6.7).
Mullany and colleagues wrote that they addressed these systemic disease features because of their association with dementia; however, they were self-reported, as they could not be objectively collected.
“Regardless, our results demonstrated an association between NTG status and cognitive impairment, which withstood a strong association between hypertension and cognitive impairment,” they wrote. “This NTG–dementia association has the potential to change our understanding of NTG and provide insight into future treatment directions.”
Perspective
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The investigation to understand the relationship between glaucoma and progressive neurological conditions resulting in cognitive impairment and dementia has been of interest for at least 25 years. There have been developments in identifying overlapping features of pathogenesis and objective findings including retinal nerve fiber layer thinning, ganglion cell loss and retinal microvascular changes. However, understanding whether glaucomatous optic neuropathy, particularly when IOP is not statistically elevated, is a primary optic neuropathy or secondary to generalized central nervous system degeneration, or a combination of the two is still not well understood.
Risk factors for the development of cognitive impairment and dementia are wide-ranging; and while systemic risk factors were included in analysis, other known risk factors including socioeconomic status, educational attainment and history of head injury were not assessed in this study.
Clinicians should be aware of the potential for patients, particularly those older than 65 years of age with NTG to have coexisting cognitive impairment, which may inform a lower threshold for referral for cognitive assessment. The negative impact of cognitive impairment on adherence to medical therapy and follow-up care should be recognized for patients with glaucoma and may inform treatment and management considerations.
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