Factors Linked to Primary Glaucoma Incidence Include Older Age, Higher IOP

Ningli Wang, MD, PhD

New findings on the incidence of primary glaucoma in a rural population in China reported a 0.4% average annual incidence rate among subjects 40 years of age and older over a 5-year period.

Factors including older age, higher intraocular pressure (IOP), and vertical cup disc ratio (VCDR) ≥0.60 at baseline were linked to the highest risk of glaucoma development.

“When extrapolating the incidence rate to the national population of China, we estimated that, annually, approximately 2.97 million people aged 40 years or older will develop primary glaucoma,” wrote study author Ningli Wang, MD, PhD, Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital.

Understanding the prevalence of eye disease may be useful in advocating for eye care resources and blindness prevention, Wang and colleagues noted. It may be more useful to determine both incidence and related risk factors to offer effective interventions to those at risk of the disease, they added.

The population-based cohort study reported important data for the 5-year incidence of primary glaucoma, including primary open-angle glaucoma (POAG) and primary angle closure glaucoma (PACG), and related risk factors obtained from follow-up of the Handan Eye Study (HES).

Participants aged 30 years or older without glaucoma at baseline attended standardized eye examinations at baseline and follow-up examination after a 5-year interval in the HES. Investigators noted the 5–year cumulative incidence of primary glaucoma was person-based and was defined as the development of primary glaucoma with definite and probable certainty in ≥1 during the 5-year follow-up.

The study performed univariate and multivariable logistic regression analyses to identify the baseline risk factors that could predict the incidence of glaucoma. The at-risk population in the study included 5184 participants (82.0%), with a median age of 52.0 years at baseline and 57.6 at follow-up.

In the 5-year follow-up, newly incident primary glaucoma developed in 82 subjects (crude incidence, 1.6%; 95% confidence interval [CI], 1.2% – 1.9%). Data show the age- and gender-standardized incidence of glaucoma among those aged ≥40 years was 2.1% and the annual age- and gender-standardized incidence was 0.4%.

In comparison to those who did not develop glaucoma, patients with developed cases were more likely to be older (P <.001), single or widowed (P = .007), hypertensive (P <.001), have a higher systolic blood pressure (P <.001) and mean blood pressure (P = 0.008). As well, patients had a lower education level (P = .038), a worse BCVA (P = .001) and a higher IOP (P = .016).

According to the univariate and multivariate logistic regression analyses, baseline risk predictors associated with incidence glaucoma were older age (odds ratio [OR], 1.06; 95% CI, 1.04 - 1.09; P <.001), higher IOP (OR, 1.11; 95% CI, 1.02 - 1.20; P = .017) and a VCDR ≥0.60 (OR, 5.30; 95% CI, 3.22 - 8.73; P <.001).

Data suggest that for each year of older age, the risk of primary glaucoma increased by 1.2% per year. Then, for each mmHg higher IOP, the risk of primary glaucoma increased by 2.0% per year.

“However, it remains to be determined in future research whether aging itself is truly a risk factor for glaucoma development or if changes to the optic nerve head with age make the eye more vulnerable to high IOP, thereby producing an underlying risk factor for glaucoma,” Wang added.

The study, “Five-year incidence of primary glaucoma and related risk factors – The Handan eye study,” was published in Acta Ophthalmologica.