A study recently published in Ophthalmology investigated the relationship of glaucoma and Alzheimer’s disease (AD).
First, give me some background.
As the world’s largest cause of permanent vision loss, glaucoma shares key pathogenic features with dementia and AD—hypothesizing a possible connection.
With prior studies yielding inconsistent results, a recent meta-analysis of 11 studies did not identify any significant association.
Thus, investigators of this research aimed to conduct the largest known study to date.
Talk about the study.
A total of 3.5 million people in Sweden were included in data collection as the investigators sought to determine long-term risks of AD, vascular dementia (VaD), and all-cause dementia associated with glaucoma.
They first identified 324,730 people diagnosed with glaucoma with no prior diagnosis of dementia from 1995-2017 using Swedish Hospital and Outpatient Registers.
Go on…
Next, each of the diagnosed patients were matched with 10 randomly sampled people from the general population in Sweden. These matches shared sex, birth month and year, and no prior diagnoses of dementia.
And the purpose?
To track the earliest diagnoses of AD, VaD, and all-cause dementia in each person, and to compare the control matches to the persons diagnosed with glaucoma.
Tell me more.
Cox regression was used for statistical analysis in this comparison, while adjusting for covariates such as education level, income, or prior registration of other ailments.
Subanalyses were also carried out for glaucoma subtypes, including primary open-angle (POAG), primary angle-closure (PACG), normal-tension (NTG), and other/unspecified.
Findings?
The control group’s incidence of all-cause dementia was 6% compared to 8% for persons with glaucoma. Median dementia diagnosis age was 74 years, with a median follow-up time of 8 years.
Expand on the association.
A significant association was identified between glaucoma and all major types of dementia. Compared with controls, persons with glaucoma of any type had a:
- >35% higher risk of AD
- ~65% higher risk of VaD
- ~55% higher risk of all-cause dementia
What about glaucoma types?
Each type of glaucoma was significantly associated with a higher risk of all-cause dementia. In both POAG and NTG, increased risk of AD and VaD were shown as well.
Finally, in PACG, VaD was associated moderately as well; however a relationship with AD was not determined.
How do other variables affect this?
No significant differences were found between sexes, but age differences did display diversification. Association was much stronger when persons were diagnosed with glaucoma at older ages.
When diagnosed with glaucoma at ≥80 years old, patients had the highest risk of developing AD or all-cause dementia.
By contrast, when diagnosed with glaucoma at <60 years old, there was not an elevated risk of developing dementia displayed.
Expert opinion?
The authors noted past studies that both confirmed and were inconsistent with their findings, commenting that this heterogeneity displayed a key need for both this study and future research.
They maintained that this study was the largest to investigate this association thus far, and that the size created an opportunity for high statistical power in accounting for both additional variables and subtypes of both diseases.
Significance?
Per the study authors, “Our findings suggest that monitoring for early symptoms of dementia, such as changes in cognitive function and memory, should be considered in the follow-up care for glaucoma patients.”
If these findings are able to be confirmed further, both patients and practitioners could gain a better understanding of what to look for, making a major difference for earlier detection and treatment.