Obesity linked to lower risk of open-angle glaucoma in women

Researchers have had a hard time pinning down which lifestyle factors are associated with open-angle glaucoma. Previous studies on socioeconomic status and smoking have not been definitive, and those on alcohol intake and obesity have been contradictory. Since many lifestyle factors are modifiable, the mixed findings of these studies deserve further evaluation.

To this end, investigators analyzed data from the Rotterdam Study to determine the effect of lifestyle-related factors on the risk of open- angle glaucoma (OAG) and IOP. 

Of 3,939 eligible participants, 108 (2.7 percent) developed OAG during a mean follow up of 9.7 years. Alcohol, socioeconomic status, education and smoking had no association with glaucoma rates in this study. Although these findings are in line with those from earlier studies, these findings are based on a relatively low number of OAG cases, and as a consequence, small effects of these lifestyle-related risk factors cannot be ruled out because of power limitations. They also note that the population of this study was rather homogenous with little variability in income, making it difficult to make significant associations.

But the most salient and confusing finding in this study was the relationship between obesity and glaucoma in women, but not in men. They found that women's risk of OAG decreased significantly as body mass index (BMI) increased. For every unit increase in BMI, women had a 7 percent lower risk of OAG.

Higher BMI was also associated with higher IOP (P < .001) in women. While the protective effect of high BMI on OAG appears to be IOP independent, an overestimation of IOP as assessed with Goldmann applanation tonometry in obese women may have contributed to the remarkable relationships between BMI and IOP and BMI and OAG in women. The authors also suggest that high estrogen levels and hormone therapy might protect obese women from OAG.