The Prevalence and Incidence of Glaucoma in Denmark in a Fifteen Year Period: A Nationwide Study

Abstract

Purpose: The purpose of the present study was to describe the prevalence, incidence and geographic variation of glaucoma in Denmark in the period from 1996 to 2011. Moreover, the aim was to identify the treatment patterns of glaucoma within the studied period.

Methods: All Danish citizens were included throughout the study period. The National Prescription Registry was used to identify all claimed prescriptions for glaucoma medication.

Results: A total of 116,592 incident glaucoma patients were identified. Average age at onset was 66 years (range: 0-105 years), 55% were women. The prevalence of glaucoma increased from 0.79% to 1.72% during the investigated period. In 2011 glaucoma affected 3.76% of the population above 50 years and 10% in patients above 80 years. The age-specific incidence rate of glaucoma seemed to be constant and the increasing prevalence was primarily attributed to an aging population. We found the highest prevalence of glaucoma in the capital region of Denmark. Within the studied period the use of prostaglandin analogs and combination drugs increased, whereas the use of β-blockers, carbon anhydrase inhibitors and parasympathomimetic drugs decreased (p<0.001). Finally, the use of α2-adrenergic agonists remained unchanged. A total of 75% of the patients were treated with two or more glaucoma medications.

Conclusions: Over all, the present study is the first to assess the frequency and the development of glaucoma in Denmark over a 15-year period. We find that glaucoma affects a little less than 2% of the total population and increases with age to reach a prevalence of more than 10% amongst people above 80 years. Generally, the present study is the largest nation-wide study ever made and must be a close-to-real-life-picture of the utilization of glaucoma medication on a national scale. Our findings confirm other recent estimations on an increasing burden of glaucoma globally.

Fig 1. Prevalence, Incidence and age distribution of glaucoma patients in Denmark.

A. Prevalence of glaucoma cases in Denmark in the period from 1996 to 2011. The percentage of female glaucoma patients above 50 years is shown in age intervals of 10 years. A significant increase in the prevalence throughout the period was found (p < 0.001). No significant difference is seen among females and males (p = 0.8). B. Incidence of glaucoma cases in Denmark in the period from 1996 to 2011. The percentage of female glaucoma patients above 50 years is shown in age intervals of 10 years. No significant difference is seen among females and males (p = 0.1). No significant change was observed in the incidence in the studied period. C. The age distribution in Denmark from 1996 and 2011. In 1996 the total population was 5.3 million and in 2011 5.6 million, respectively. Numbers are drawn from the Danish National Patient Registry. D. The age specific incidence rates of glaucoma in Denmark in the period from 1996 to 2011. Out of a total of 116,594 cases, the incident rates reveal a bell shaped distribution with a peak at the age of 80 years by 600 cases per 100,000 person-years.

Fig 2. The demographic variation of glaucoma patients in Denmark.

The map illustrates the differences in the prevalence of glaucoma cases in the age group from 50 to 60 years. The highest prevalence of glaucoma is found in the capital region of Denmark with a prevalence of 6.28%, which was significantly higher compared to the other regions (Table 3). 1) The Capital Region of Denmark, 2) Region of Zealand, 3) Region of Southern Denmark, 4) Region of Central Jutland, 5) The North Denmark Region.

Fig 3. Total distribution of “first of choice” glaucoma medication in Denmark in the period from 1996 to 2011.

The distribution of “first of choice” medication is shown throughout the study period. The use of β-blockers has decreased (p < 0.001), whereas the use of prostaglandin analogs and combination drugs has increased in the studied period (p < 0.001). The lower figure shows the time line of the introduction of glaucoma medication (modified from European Guidelines, 4^th edition). Abreviations: β-block., β-blockers; Prostagl., prostaglandin analogs; α-adren., α2-adrenergic agonists; Paras., parasympathomimetic drugs; CAI, carbon anhydrase inhibitors; Comb., combination drugs.