New OHTS analyses revisit protective effect of diabetes mellitus

Updated analyses of data from the Ocular HypertensionTreatment Study (OHTS) failed to confirm the original finding that a history of diabetesmellitus protects against progression from ocular hypertension to primary open-angle glaucoma(POAG), said Michael A. Kass, MD.

The analyses considered three definitions to identify patients as having a history of diabetesmellitus using new information collected after publication of the original OHTS predictivemodel, said Dr. Kass, Washington University School of Medicine, St. Louis, MO. The firstdefinition was based on the same medical history question posed originally that asked patientswhether a physician had ever told them they had diabetes or sugar in their blood. The secondquestion asked patients whether a physician or health professional had recommended a specialdiet to lower their blood sugar. The third question asked patients whether they were taking insulin or diabetic pills to lower their blood sugar.

The number of patients with an affirmative response to each of these questions was 409, 277,and 256, respectively. At the baseline exam, 191 patients were categorized as having a historyof diabetes based on their response to the medical history question.

In univariate and multivariate analysis using the refreshed data, a history of diabetes was notassociated with the development of POAG for any of the three definitions tested. Themultivariate hazard ratios for the three analyses ranged from 0.73 to 0.84 and all had 95%confidence intervals including "1."

"The original finding of a protective effect of diabetes mellitus was unexpected and puzzling,"Dr. Kass said. "Considering the potential limitation of our ascertainment method, we decided toget additional data on self-reported diagnosis to evaluate this finding further.

"Using new definitions to categorize patients as having diabetes showed no evidence of aprotective effect," Dr. Kass added. "These updated findings are consistent with previousstudies that reported diabetes mellitus either increased the risk of developing POAG or had noeffect."