Purpose
To explore the association between marijuana use and glaucoma in US noninstitutionalized subjects who were over the age of 40 years and participated in the National Health and Nutrition Examination Survey (NHANES).
Methods
In a cross-sectional study using the 2005-2006 and 2007-2008 NHANES databases, participants were included if they had demographic data and were over the age of 40 years, had self-reported questionnaires, optic nerve photographs, and frequency doubling technology (FDT) visual fields perimetry collected as part of the NHANES survey. The exposure of interest was self-reported marijuana use (ever used marijuana or hashish). The outcomes of interest were a clinical diagnosis of glaucoma based on the Rotterdam criteria including signs of glaucoma damage seen in optic nerve photographs and FDT visual fields perimetry, and a self-reported glaucoma (ever told had glaucoma). Logistic regression modeling was performed to assess the association between marijuana use and glaucoma after controlling for age and ethnicity as potential confounders. All estimates were weighted based on the multistage NHANES sampling design.
Results
Among participants who met the inclusion criteria, the overall prevalence of the clinical diagnosis of glaucoma and self-reported glaucoma were 4.3% (139 of 3250) and 4.3% (218 of 5021), respectively. The overall prevalence of self-reported marijuana use was 54.3% (1576 of 2901). There was an increased odds of having a clinical diagnosis of glaucoma for self-reported marijuana use (odds ratio [OR]=1.43, 95% confidence interval [CI]=0.93, 2.18), while there was a decreased odds of having self-reported glaucoma for self-reported marijuana use (OR=0.66, 95% CI=0.39, 1.11).
Conclusions
In NHANES, participants who had self-reported marijuana use tended to have a higher odds of a clinical diagnosis of glaucoma and a lower odds of having self-reported glaucoma. Such apparently contradictory results suggest that there may be a selection bias in subjects who self-report glaucoma because marijuana use is perceived to have beneficial effects for decreasing intraocular pressure. Another possible explanation is that marijuana use actually may increase glaucomatous optic nerve damage. These findings indicate the need for further research to elucidate the effect of marijuana on glaucoma, especially as more states legalize marijuana use.