Major Finding: Higher BMI is not associated with a higher risk of POAG, and in women, it was associated with a 6% risk reduction in normal-tension glaucoma.
Data Source: Prospective cohort study of 78,777 women in the Nurses Health Study and 41,352 men in the Health Professionals Follow-Up Study, from which 980 cases of POAG were identified.
Disclosures: The investigators reported no conflicts of interest. The study was funded by grants from the National Institutes of Health.
Higher body mass index is not associated with a higher risk of primary open-angle glaucoma, and in women, it may be associated with a reduced incidence of normal-tension glaucoma, a study has shown.
Even so, clinicians and patients must be cautious about these findings until further research substantiates them and clarifies the related biologic mechanisms, cautioned lead researcher Dr. Louis R. Pasquale of the department of ophthalmology, Harvard Medical School, and the Massachusetts Eye and Ear Infirmary, both in Boston, and his colleagues.
The findings are based on data from a prospective cohort study of 78,777 women in the Nurses Health Study and 41,352 men in the Health Professionals Follow-Up Study. Researchers followed participants in the NHS from 1980 through 2004 and participants in the HPFS from 1986 through 2004 (Ophthalmology 2010 [doi:10.1016/j.ophtha.2009.12.017]).
Eligible patients were aged 40 years and older, did not have primary open-angle glaucoma (POAG) at baseline, and underwent eye examinations during follow-up.
Participants in both studies completed questionnaires with information about anthropometric measures, potential confounders, and ophthalmic status. Also, researchers evaluated medical records, including visual field data, from participants who self-reported glaucoma.
For statistical analysis, they divided the incident cases by person-years accrued for each category of anthropometric measure, controlled for known risk factors for POAG, and determined the relationship between anthropometric measures and POAG subtype, namely high tension (more than 21 mm Hg) and low tension (21 mm Hg or less).
The researchers identified 980 cases of POAG during follow-up. Overall, they found no associations between cumulatively averaged BMI and either POAG subtype, and no association between height and the risk for POAG. In women, however, they found that every unit increase in BMI was associated with a 6% reduction in the risk for normal-tension glaucoma.
“Although the inverse association between weight residuals and normal-tension POAG among women may be the result of chance, it is reasonable to entertain [biologic] mechanisms that may support such an association,” the researchers reported. “Perhaps some measure linked to adiposity or lean mass that is under sex hormonal influences may protect against the development of POAG. It is possible that higher circulating estrogen levels in postmenopausal women with higher BMI bind to estrogen receptors expressed on retinal ganglion cells to mediate neuroprotection.”
By determining how anthropometric measures influence a patient's risk of developing POAG, the researchers wrote, they may one day unlock important clues regarding disease pathogenesis.