Smoking and multivitamins shown as risk factors for dry eye

Study finds 14.4% overall prevalence; surprisingly, caffeine was not a factor.

MADISON, U.S.A. — Smoking and multivitamin use may worsen the symptoms of dry eye syndrome, according to a large cross-sectional study. On the other hand, caffeine consumption and a higher total to high-density lipoprotein (HDL) cholesterol ratio were associated with less dry eye.

“Dry eye is like the back pain of ophthalmology. They are nebulous and elusive conditions that remain after you eliminate every other cause,” said Scot E. Moss, MA, a researcher in the department of ophthalmology and visual sciences at the University of Wisconsin here. “Dry eye is also difficult to treat.”

The study, which was published in Archives of Ophthalmology, estimated the prevalence of dry eye in the population of the Beaver Dam Eye Study and explored its relationship with various risk factors. The cohort consisted of 3,703 participants ranging in age from 48 to 91 years (mean age 65). Men comprised 43% of the population, and 99% of the subjects were white.

Adjusted for age, the prevalence of dry eye syndrome was 11.4% in men and 16.7% in women for the 5-year follow-up study.

Smoke gets in your eyes

Not surprisingly, the researchers found smokers were much more susceptible to dry eye syndrome. Current smokers had an odds ratio of 1.82 and past smokers 1.22. “When you smoke, smoke gets in your eyes,” Mr. Moss told Ocular Surgery News. “Certainly if a dry eye patient smokes, he should be advised to stop.” Symptoms are also worse during the heating season, when air is dryer. “Using a humidifier to add a little moisture to the air might help,” Mr. Moss said.

Multivitamin use was also associated with dry eye syndrome. Current users had an odds ratio (OR) of 1.41 and past users 1.35. In contrast, caffeine was not found to be a risk factor (OR 0.75). “This is somewhat surprising,” Mr. Moss said. “Most of the caffeine in this population was consumed in the form of coffee. Because coffee acts as a diuretic, you would think it would make your eyes feel more dry. But we found the opposite.”

Mr. Moss speculated that “people with dry eyes may have stopped drinking coffee because of its diuretic effect, so it appears cross-sectionally that there would be an inverse relationship.” This same reasoning may also hold true for multivitamin use. “People with dry eyes may be taking vitamins to achieve positive effects. So if you look at the people who are taking vitamins, you are going to find that they have more dry eye symptoms. But these two variables may not be related at all,” Mr. Moss said.

Lipid layer important

Total to HDL cholesterol ratio also had a positive effect (0.93 OR). “Individuals with a higher total to HDL cholesterol ratio were less likely to have dry eye,” Mr. Moss said. “This may be related to the fact that the tear layer has three distinct layers: a mucous layer closest to the eye, an aqueous layer and a lipid layer on top. The purpose of the lipid layer appears to be to prevent evaporation. Therefore, people without a good lipid layer are going to have increased evaporation of their tears and hence they are going to have dry eyes. People with more cholesterol may have a better lipid layer to their eyes.” However, “the HDL cholesterol by itself was not associated with dry eye,” Mr. Moss said.

Three other factors independently and significantly associated with dry eye in a logistic model were history of thyroid disease (OR 1.41), history of gout (OR 1.42) and diabetes (OR 1.38).

Confirmed prevalence

The overall prevalence of dry eye in the study was 14.4%, which is similar to the other two large population studies. The Salisbury Eye Evaluation study reported a prevalence of 15%, based on the frequencies of six symptoms in a population with a mean age of 73.5 years. In that study, 15% of the population was black.

The Melbourne study reported a lower prevalence of dry eye, based on a set of six symptoms that were different from the Salisbury study. However, the Melbourne study had a younger enrollment (mean age 59 years). That study found 7.4% reporting at least two symptoms and 5.3% reporting any severe symptom not attributed to hay fever.

“Because we don’t have longitudinal data at this time, the next best step would be to look at people who develop dry eye over a period of time and then evaluate their risk factors at the beginning,” Mr. Moss said.

For Your Information:

• Scot E. Moss, MA, can be reached at Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, 610 N. Walnut St., 460 WARF, Madison, WI 53705-2397 U.S.A.; +(1) 608-263-8837; fax: +(1) 608-263-0279; e-mail: moss@epi.ophth.wisc.edu. Mr. Moss has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.