Women with higher body mass indexes (BMIs) are less likely to develop normal tension glaucoma, according to a study in the August issue of Ophthalmology.

Body mass index is a measurement of an individual’s body fat content in relation to his or her lean body mass tissues, such as muscle, blood and bone. Typically, higher BMI measurements are associated with an increased risk for several devastating conditions, including heart disease and type 2 diabetes.

In this study, the researchers evaluated 78,777 females enrolled in the Nurses Health Study (1980-2004) and 41,352 males enrolled in the Healthy Professionals Follow-up Study (1986-2004). Following data analysis, the researchers determined that each BMI unit increase in women from baseline measurement resulted in a 6% reduction in risk for the development of normal tension primary open-angle glaucoma (defined as an IOP equal to or less than 21mm Hg).

However, no such association between increased BMI and lower glaucoma risk was documented in men.

“Understanding the mechanisms that drive BMI and other body composition factors in relation to primary open-angle glaucoma might help us solve some mysteries connected with this complex illness,” said lead author Louis R. Pasquale, M.D., director of the Massachusetts Eye and Ear Infirmary in Boston. “It is reasonable to speculate that hormonally-controlled factors released from adipose or lean tissues may alter the risk of normal tension glaucoma in women. Higher BMI in postmenopausal women is linked with higher estrogen levels, which might positively affect estrogen receptors in the optic nerve.”

Nevertheless, because of the potential health risks associated with increased BMI measurements, Dr. Pasquale and his associates suggest that both clinicians and patients be cautious about interpreting these findings until further research clarifies the related biological mechanisms.

Pasquale LR, Willett WC, Rosner BA, Kang JH. Anthropometric measures and their relation to incident primary open-angle glaucoma. Ophthalmology. 2010 Aug;117(8):1521-9.