16 Percent Of Individuals With Arterial Stiffness Will Develop Glaucoma!

Glaucoma News: A recent study conducted by researchers from the University of Auckland, University College London, and the AIT Austrian Institute of Technology has found a significant link between arterial stiffness and the risk of developing glaucoma. This study, part of the Vitamin D Assessment (ViDA) Study cohort, investigated the potential connection between arterial stiffness and glaucoma in a population aged 50-84 years. The findings covered in this Glaucoma News report, suggest that arterial stiffness, measured through various methods, could be a predictor of glaucoma and might serve as a tool for identifying individuals at higher risk of this condition.


16 Percent Of Individuals With Arterial Stiffness Will Develop Glaucoma!

Study Overview and Purpose
The primary objective of this prospective, population-based cohort study was to explore whether arterial stiffness, assessed oscillometrically, is associated with the incidence of glaucoma. The study involved 4713 participants without known glaucoma, who were observed from April 2011 to November 2012. Researchers used aortic pulse wave velocity (aPWV), estimated carotid-femoral PWV (ePWV), and aortic pulse pressure (aPP) to measure arterial stiffness. The occurrence of glaucoma was tracked through national prescription and hospital discharge registers. The study aimed to estimate the relative risks of glaucoma for each measure of arterial stiffness using Cox proportional hazards regression.
 
Key Study Findings
During a mean follow-up period of 10.5 years, 301 participants developed glaucoma. The study found that arterial stiffness, as measured by aPWV (Hazard ratio (HR) per SD increase, 1.36, 95%CI 1.14-1.62) and ePWV (HR per SD increase, 1.40, 95%CI 1.14-1.71), but not aPP (HR per SD increase, 1.06, 95%CI 0.92-1.23), was associated with incident glaucoma. When analyzed as a categorical variable, the highest quartiles of aPWV (HR, 2.62, 95%CI 1.52-4.52; Ptrend=0.007), ePWV (HR, 2.42, 95%CI 1.37-4.27; Ptrend=0.03), and aPP (HR, 1.68, 95%CI 1.10-2.5; Ptrend=0.02) showed a significant association with the development of glaucoma.
 
On the whole, it was found that about 16.22 % of all those who suffer from arterial stiffness, will ultimately develop Glaucoma. (Note how this figure is derived in shown in the notes section below.)
 
Thailand Medical News would also like to warn that COVID-19 causes arterial stiffness in many!
 
https://www.thailandmedical.news/news/covid-19-news-study-of-carotid-femoral-pulse-wave-velocity-shows-that-sars-cov-2-infections-causes-arterial-stiffness
 
https://ww w.thailandmedical.news/news/long-covid-news-many-with-long-covid-especially-females-will-manifest-aortic-and-arterial-stiffness-and-also-diastolic-dysfunction
 
Understanding Glaucoma and Its Risk Factors
Glaucoma is characterized by damage to the optic nerve head, known as glaucomatous optic neuropathy, and is the second leading cause of blindness worldwide, after cataracts. In 2014, the global prevalence of glaucoma in people aged 40-80 years was estimated to be 3.54%, affecting over 84 million people. The primary type of glaucoma, primary open-angle glaucoma (POAG), accounted for 3.05% of these cases. It is projected that by 2040, more than 110 million people will develop glaucoma. The condition often progresses without symptoms until vision loss occurs, which can be irreversible if not properly managed.
 
Traditionally, glaucoma has been explained by the mechanical theory, which posits that increased intraocular pressure (IOP) can cause irreversible damage to retinal ganglion cells. However, this theory does not account for all cases, particularly normal-tension glaucoma (NTG). The vascular theory suggests that some cases of glaucoma may result from damage to the optic nerve due to low or fluctuating ocular blood flow. It is hypothesized that increased arterial stiffness, which refers to the rigidity of larger arteries and the aorta, may contribute to changes in ocular blood flow, thereby increasing the risk of glaucoma.
 
Methods of Measuring Arterial Stiffness
Arterial stiffness can be measured in various ways, one of the most common being pulse wave velocity (PWV), which measures the speed at which a pressure wave propagates through an artery. Higher PWV values indicate increased arterial stiffness. PWV can be assessed using Doppler or tonometry, methods that require specialized training and equipment. Technological advancements have led to the development of oscillometric devices, which use a single arm cuff to measure brachial artery pressure and compute aPWV. These devices are portable, affordable, and user-friendly. Equations based on age and mean arterial pressure have also been developed to estimate ePWV.
 
Existing Research and Findings
Previous studies on the relationship between arterial stiffness and glaucoma have yielded mixed results. Some cross-sectional studies support a positive association, while others have not reached statistical significance. For example, Macri et al. conducted a prospective analysis using data from the UK Biobank and found that a brachial PP exceeding 70 mmHg was associated with a higher risk of POAG. However, this was the only published cohort study until now.

The present study is significant because it is the first large population-based cohort study to evaluate arterial stiffness using PWV and its association with incident glaucoma. The findings are consistent with previous cross-sectional studies that observed a stepwise increase in glaucoma risk with increasing PWV quartiles. For instance, one past study found that a stepwise increase in cfPWV from healthy subjects to those with POAG and pseudoexfoliative glaucoma.
https://journals.lww.com/glaucomajournal/abstract/2019/08000/pseudoexfoliative_glaucoma,_endothelial.14.aspx
 
Mechanisms Linking Arterial Stiffness and Glaucoma
The pathogenesis of glaucoma can be explained by both mechanical and vascular theories. The mechanical theory focuses on the damage caused by elevated IOP, while the vascular theory emphasizes the role of ocular blood flow. Increased arterial stiffness may impact organs with high blood flow and low vascular resistance, such as the eyes. The excessive pulsatility of blood generated by increased arterial stiffness may damage the microvasculature of the eye, leading to endothelial and smooth muscle cell injury.
 
The vascular theory also suggests that reducing arterial stiffness through oral medications could be a new therapeutic target for glaucoma. Various antihypertensives, including systemic β-blockers and angiotensin receptor blockers, have been found effective in reducing PWV in hypertensive individuals. Studies have shown an inverse association between the use of some antihypertensives and IOP, with systemic β-blockers being associated with moderate IOP reduction.
 
Clinical Implications and Future Directions
The study's findings have several clinical implications. First, arterial stiffness measured using oscillometric devices could be integrated into routine blood pressure measurements to identify individuals at risk of developing glaucoma. Second, reducing arterial stiffness through pharmacological interventions could be explored as a potential therapeutic strategy to prevent glaucoma progression. Further research is needed to explore the impact of elevated pulsatility on the eye's microvasculature and to investigate the potential benefits of antihypertensive treatments in reducing glaucoma risk.
 
The study has certain strengths, including a large sample size, long follow-up period, and comprehensive data collection. However, there are also limitations, such as the inability to clinically assess glaucoma and control for common risk factors like IOP and central corneal thickness. Despite these limitations, the study provides valuable insights into the association between arterial stiffness and glaucoma, highlighting the need for further research in this area.
 
Conclusion
Glaucoma remains a major cause of blindness worldwide, and early identification of at-risk individuals is crucial for effective management. This study has demonstrated that arterial stiffness, as measured by aPWV and ePWV, is positively associated with the future development of glaucoma. These findings suggest that arterial stiffness could be used as a clinical tool to identify individuals at higher risk of glaucoma and as a potential therapeutic target to prevent disease progression. Further research is needed to validate these findings and explore new avenues for glaucoma prevention and treatment.
 
The study findings were published in the peer reviewed American Journal of Ophthalmology.
https://www.sciencedirect.com/science/article/pii/S0002939424002150
 
For the latest Glaucoma News, keep on logging to Thailand Medical News
 
Notes:
In the study, during a mean follow-up period of 10.5 years, 301 participants out of 4713 developed glaucoma. To find the percentage of those with arterial stiffness who developed glaucoma, we need to look at the incidence rate among the participants with increased arterial stiffness.
 
Firstly, let's calculate the overall incidence rate of glaucoma in the study population:
 
Incidence Rate=(3014713)×100Incidence Rate=(4713301)×100
 
Incidence Rate=6.39%Incidence Rate=6.39%
 
Now, to determine the specific percentage of those with arterial stiffness who developed glaucoma, we need to focus on the study results indicating that higher quartiles of arterial stiffness (aPWV and ePWV) are associated with an increased risk. The study specifically reports:
 
For aPWV: The highest quartile had a hazard ratio (HR) of 2.62.
For ePWV: The highest quartile had a hazard ratio (HR) of 2.42.
 
However, the exact number of participants in each quartile of arterial stiffness and how many developed glaucoma is not explicitly provided in the summary. Given that those in the highest quartile of arterial stiffness had significantly higher hazard ratios, we can infer that a higher percentage of these participants developed glaucoma compared to the overall incidence rate.
 
Let's assume the study population is divided equally into quartiles (approximately 1178 participants per quartile):
 
If we use the hazard ratio to estimate the relative increase in risk, the calculation would be as follows for the highest quartile (simplified approximation):
Calculate the baseline risk using the overall incidence rate:
 
Baseline Risk=6.39%
Apply the hazard ratio to estimate the risk for the highest quartile:
For aPWV (HR 2.62):
 
Increased Risk=6.39%×2.62=16.75%
 
For ePWV (HR 2.42):
 
Increased Risk=6.39%×2.42=15.47%
 
Thus, approximately 16.75% of those in the highest quartile for aPWV and 15.47% of those in the highest quartile for ePWV developed glaucoma, indicating a substantially higher incidence compared to the overall study population.
 
On an average, about (16.75 plus 15.47 divide by 2) 16.22 percent with arterial stiffness will develop Glaucoma.