Heavy smoking promotes glaucoma
Smokers who consume a greater number of cigarette packs per day are highly likely to develop glaucoma, according to a study.
The study included 3,864 individuals aged ≥40 years, among whom 212 (5.5 percent) had glaucoma. This number corresponded to a population-weighted glaucoma prevalence of 3.7 percent in a total of 83,570,127 individuals. Population-weighted proportions of current and ex-smokers were 20.6 percent and 28.3 percent, respectively.
Compared with participants without glaucoma, those who had the eye disease were older (63.0 vs 56.1 years; p=0.002), likely to be male (57.1 percent vs 49.2 percent; p=0.03), to be black (36.3 percent vs 20.7 percent; p<0.001), and to have diabetes (18.9 percent vs 12.4 percent; p=0.006) or hypertension (50.5 percent vs 39.7 percent; p=0.003).
In univariate logistic model, the odds of glaucoma were lower in current smokers than in nonsmokers (odds ratio [OR], 0.61; 95 percent CI, 0.41–0.88; p=0.009) and ex-smokers (OR, 0.46; 0.28–0.76; p=0.002). The effect estimates were comparable in adjusted models, although not statistically significant.
However, greater pack/day of smoking history among ex- and current smokers combined was associated with significantly higher odds of glaucoma (OR, 1.70; 1.08–2.67; p=0.02).
The present data suggest that the protective effects of smoking, if there are any, may be eliminated in heavy smoking. Researchers called for eye-health care providers to consider this association when counselling patients on their smoking habit.
Nicotine has been shown to exert protective mechanisms on the optic nerve circulation, inducing the liberation of nitric oxide from perivascular nitrergic neurons, resulting in vasodilatation. [Am J Ophthalmol 2011;152:219-228; Prog Retin Eye Res 2007;26:205-238]
However, while high levels of nitric oxide can produce beneficial vasodilation that leads to increased optic nerve blood flow, nitric oxide can also lead to hyperperfusion damage and reactions that form peroxynitrites—free radicals that cause retinal ganglionic cell death. [Arch Ophthalmol 2011;129:773-780]
Therefore, it is possible that cigarette smoking or nicotine may be both detrimental and protective effects on the optic nerve, researchers said.