Obesity Linked to Lower Glaucoma Risk in Women
Reported February 24, 2011
Obesity was associated with higher intraocular pressure (IOP), but paradoxically seemed to have a protective effect against open-angle glaucoma (OAG) at least for women in data from the population-based Rotterdam Study.
The apparent protective effect is reported in a paper by Wishal D. Ramdas, MD, MSc and colleagues that was posted online February 14 and will appear in the May print issue of the Archives of Ophthalmology.
Dr. Ramdas told Medscape Medical News: “The association between higher [body mass index (BMI)] and higher IOP but lower risk of OAG is indeed contradictory. However, we think that the relationship of BMI with IOP is a false-positive relationship caused by the method used for the IOP measurement.” Dr. Ramdas is in the departments of epidemiology and ophthalmology at Erasmus Medical Center in Rotterdam, the Netherlands.
IOP was measured in this study using Goldmann applanation tonometry performed behind the slitlamp. “If a person is obese, it is more likely that the ophthalmologist has to push the slitlamp table against the breast of the patient. Especially in women, this might work like a Valsalva maneuver and as a consequence cause an increase in IOP,” Dr. Ramdas explained.
The analysis included data from 3939 participants in the Rotterdam Study, all of whom were 55 years of age or older, lived in a suburb of Rotterdam, did not have OAG when the study began between 1991 and 1993, and participated in at least 1 follow-up between either 1997 and 1999 or 2002 and 2006.
Over an average of 9.7 years of follow-up, 108 participants (2.7%) developed OAG. This subgroup was significantly older, more likely to have high myopia, and more likely to be male compared with participants who did not develop OAG.
Among women, there was a significant association between increased BMI and intraocular pressure. However, each 1-unit increase in BMI was associated with a 7% decreased risk of developing OAG. These associations were not present in men.
The researchers found no association between OAG and a number of other potential risk factors, including smoking, alcohol intake, IOP, ethnicity, and socioeconomic status. The relatively small number of cases of OAG that developed in this group over time, however, limits the power of the trial, and therefore any inference that can be drawn about these factors and the risk for OAG.
Dr. Ramdas said, “The inverse association of BMI with OAG was indeed a bit surprising. The fact that we only found an association in women gives rise to other questions. One of them might be the involvement of female hormones in the pathophysiology of OAG. However, conflicting results have been reported regarding the latter, and thus, further research is needed to clarify this.”
Dr. Ramdas added, “A similar finding of BMI to OAG has been reported last year. Ophthalmologists may want to pay extra attention when measuring a high IOP (using Goldman tonometry) in an obese person, especially women.”
Louis R. Pasquale, MD, director of the Glaucoma Service at the Massachusetts Eye and Ear Infirmary in Boston, reviewed the article for Medscape Medical News.
He noted: “The positive association between BMI and IOP may be more artifactual than physiological. The inverse relation between BMI and [primary OAG (POAG)] seems to be real, as this is the second study to show it. In fact the 7% reduction in risk for each unit increase in BMI is nearly identical to what we found in the Nurses’ Health Study. It represents another piece of evidence indicating that declining estrogen levels are important in POAG pathogenesis for women. Heavier women have higher estrogen levels, and estrogen has neuroprotective effects in animal models of glaucoma. Of course, more work is needed to prove that estrogen levels explain the inverse relation between BMI and POAG risk in women.”
Support for this study was provided by Topcon Europe BV, Capelle aan de IJssel, and Heidelberg Engineering. Dr. Ramdas and Dr. Pasquale have disclosed no relevant financial relationships.
Arch Ophthalmol. Published online February 14, 2011.
Reported by Janis C. Kelly
From Medscape Medical News