Cannabis smoking and glaucoma in the UK Biobank cohort.

BACKGROUND

Cigarette smoking is a well-known risk factor for primary open-angle glaucoma (POAG). Tobacco smoke contains a variety of chemicals, including nicotine, free radicals, and carbon monoxide, all of which can play a role in the development of POAG. Cannabis smoke, like tobacco smoke, contains a comparable variety of carcinogenic and toxic compounds. In the present study, we analyzed UK Biobank data to determine whether smoking cannabis, like cigarettes, might be related to POAG.

METHODS

Our analysis included all subjects with glaucoma and cannabis smoking information. Data processing was performed on Minerva, a Linux mainframe with Centos 7.6, at the Icahn School of Medicine at Mount Sinai. We used the UK Biobank Data Parser (ukbb parser), a python-based package that allows easy interfacing with the large UK Biobank dataset. Statistical analysis was performed with SPSS 25 and R.

RESULTS

Subjects who used cannabis 100 times or more were significantly younger (10years) when they developed glaucoma than subjects who never used cannabis. The effects of age (P<0.001) and cigarettes (P=0.014) on POAG incidence were significant, but the effect of cannabis use was not (P=0.662). The effect of cannabis use on age at glaucoma diagnosis was significant and unrelated to the effects on intraocular pressure or cigarette pack-years smoked. Analysis of intraocular pressure showed that mean pressures of subjects who used cannabis 11-100 times were significantly lower than those who took no cannabis.

CONCLUSION

Inhaling cannabis smoke is injurious to the eye, but in the case of glaucoma the manifestations are different from those of inhaled tobacco smoke. Cannabis reduces intraocular pressure but accelerates glaucoma development. Cannabis does not increase risk of glaucoma. Cigarette smoking increases risk of glaucoma and significantly accelerates glaucoma development. Apparently, early use of cannabis leads to the earlier development of glaucoma.