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Editors Selection IGR 8-3

Alzheimer

Comment by Neeru Gupta on:

14277 High frequency of open-angle glaucoma in Japanese patients with Alzheimer's disease, Tamura H; Kawakami H; Kanamoto T et al., Journal of the Neurological Sciences, 2006; 246: 79-83

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The question of whether clinical and genetic associations exist between open angle glaucoma and Alzheimer's disease is an interesting one. In this study by Tamura et al. (839), 172 AD patients and 176 age matched controls were included. POAG was found in 24% of AD patients compared to 10% in the control group. The authors concluded that the prevalence of POAG is significantly higher in Japanese patients with AD compared to control subjects, suggesting that common factors contribute to the two diseases.

The most important challenge in interpreting this study is that patients with AD came from 4 different Japanese institutions. These AD patients were compared to controls without AD, and controls also came from three different Japanese hospitals/institutions. The differing source populations for AD patients and controls, significantly limits their comparability. For example, patients with clinically overt glaucoma would be less likely to frequent hospitals without eye departments, artificially lowering the prevalence of glaucoma in the control group.

Additional considerations raised by this study include whether patients without AD were assessed for cognitive, neurological or ocular diseases, and whether in the AD diagnostic criteria, vascular dementia was included. Cup to disc ratios greater than 0.7 were classified as glaucoma by specialists unblinded to the clinical diagnosis, and different IOP measuring methodologies were used depending on the group studied. Patients with AD and POAG compared to those with AD without POAG were significantly older in age. Regarding the frequency of APOE e 4 in glaucoma, a susceptibility gene for AD, cases from one source population were compared to controls from another source population The authors examined 3

APOE alleles in 28 patients with AD and OAG, 94 patients with AD without OAG and 77 control patients. The authors concluded that the frequency of APOE 4 allele in AD patients with POAG was not significantly higher than that AD patients without OAG. Studies of a large sample size and adequate design without selection bias will be needed to understand potentially important interactions between insults from glaucoma and AD.

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