Using the UPDB to Assess Familial Risk of Primary Open Angle Glaucoma

Abstract

Purpose: : Primary open angle glaucoma (POAG) is the second most prevalent cause of irreversible blindness in the elderly. Previous epidemiological studies have identified family history, ethnic origin, age, high intraocular pressure and diabetes mellitus as risk factors. It is difficult to assess, however, to what extent family history plays a role. The Utah Population Database (UPDB), created by the University of Utah, has more recently become a resource where over 9 million records can be utilized. There are two major data sets from which family members can be identified: 1.6 million geneology records and 2 million Utah birth certificates. The purpose of this study was to utilize these resources to assess the familial risk of POAG.

Methods: : The University of Utah's 1.5 million hospital and clinic records were searched for patients with primary and chronic open angle glaucoma (ICD9 codes 365.04 and 365.11) between the years 1995–2005. A case–control analysis was then performed with specialized UPDB software that was modified to constrain the control and pedigree populations to over one million University of Utah–UPDB linked records. Controls were matched to cases by gender and birth year +/– 2.5 years and only one control was picked per case. Population of attributable risk to familial factors (PAR) and relative risk (RR) were computed using conditional logistic regressions (CLR).

Results: : 6198 patients with glaucoma were identified from the original 1.5 million medical records. 3391 of the 6198 patients were used in the study; the others were not used since they had no parents and no children identified in the UPDB. The adjusted population attributable risk (PAR), using the CLR computations, was found to be 0.09, with 9% of the risk for glaucoma attributable to a genetic factor. CLR computations also showed increased relative risks in first cousins (1.45), second cousins (1.19), siblings (3.76), parents (6.25) and children (6.77).

Conclusions: : Based on the familial data there is a significantly higher prevalence of glaucoma in both first and second generation relatives than the relatives in the control group. However, when compared with other epidemiologic analysis such as one which analyzed first–degree relatives of patients from the Rotterdam study with showed a PAR of 16%, this study shows less of a familial contribution to glaucoma. The UPDB is a valuable and unique resource providing a large population from which to analyze familial risk of glaucoma.

Keywords: clinical (human) or epidemiologic studies: prevalence/incidence • genetics