Lifestyle Choices May Affect Vision Down the Road

Larry Hand

March 13, 2014

Three modifiable lifestyle behaviors — smoking, drinking alcohol, and physical activity — may be associated with loss of vision over the course of a 20-year period, but not necessarily in the way people would think, according to an article published online March 3 in Ophthalmology.

Ronald Klein, MD, MPH, from the University of Wisconsin–Madison School of Medicine and Public Health Department of Ophthalmology and Visual Sciences, and colleagues analyzed the records of 4926 individuals who participated in the Beaver Dam Eye Study baseline examination in 1988-1990. Of those, 1913 participants continued with follow-up until 2008-2010. The study population was 99% white, with a baseline age of 43 to 84 years.

Researchers conducted a standardized interview and examination at 5-year visits and collected demographic characteristics and smoking, alcohol consumption, and physical activity status. They used the Wisconsin Age-Related Maculopathy Grading System to assess the presence and severity of age-related macular degeneration (AMD).

They calculated changes for each 5-year interval between examinations by subtracting the number of letters read correctly on a visual acuity chart at baseline from the number of letters read correctly at each 5-year examination. They then calculated incidence of visual impairment (VI) in persons whose visual acuity was 20/40 or higher in 1 or both eyes at the beginning of each 5-year examination.

In computerized modeling, the researchers used a generalized estimating equation method to calculate incidence of impairment, accounting for age, examination period, sex, and possible interactions first, and then accounting for household income, cataract status, and AMD severity. From there, they built 2 models to consider smoking, alcohol, and physical activity and interactions between each behavior and age, sex, or examination period.

Overall, participants lost a mean of 1.6 letters between 5-year intervals, for a total loss of 6.6 letters over the course of 20 years. Cumulative VI incidence over the course of 20 years came to 5.4%.

"Incident VI increased with age from 0.1% in an interval for those aged 43 to 54 years at the start of the interval to 14.6% for those aged ≥ ≥85 years," the researchers write. "The 20-year cumulative incidence increased from 1% in those aged 43 to 54 years at baseline to 60% in those aged 75 to 84 years at baseline."

Smoking Had Most Effect

When researchers adjusted for age, income, and AMD severity, smoking was associated with greater numbers of letters lost, and drinking no alcohol during the past year and being sedentary were associated with higher odds of VI incidence compared with drinking occasionally and being physically active.

Adjusting for age and examination period, current smokers carried 65% increased odds of VI incidence, heavy drinkers carried 166% increased odds, and nondrinkers carried 95% increased odds, whereas physically active individuals carried 58% decreased odds compared with never smokers, occasional drinkers, and sedentary individuals. Only smoking status (P = 0.004 adjusted) and number of flights of stairs climbed (P = 0.02 unadjusted) were statistically significant for change in visual acuity.

For each 5-year interval, current smokers lost more than 0.44 letters more than never smokers lost.

"[T]his report provides evidence that modifiable behaviors such as regular physical activity may have a protective effect for incident VI and that smoking may have deleterious effects on vision," the researchers write.

They conclude, "[W]e report that the 3 modifiable factors of cigarette smoking, drinking alcoholic beverages, and physical activity are associated with changes in vision in the [Beaver Dam Eye Study] cohort. It remains to be seen whether changes in these factors will result in fewer incident cases of VI in the aging population."

Few Long-term Studies

"There have been essentially very few long-term studies that have looked specifically at the functional loss of vision and the relationship to these lifestyle factors," Dr. Klein told Medscape Medical News. This new study "gives information collected over a long period of time with enough exposure to give enough power to look at these relationships."

He said more than 300 articles have been published about the Beaver Dam Eye Study, but he cautioned against generalizability.

"I'd be very cautious about generalizing it to racially diverse groups. I think the most important point is [that] exposure to being more physically active seems to be associated with lower risk of developing visual impairment over a 20-year period."

Other uncontrolled confounders may be involved, he said. For instance, they did not control for diet. However, "[p]eople who exercise may also have better diets," he said. "I think people need to be cautious when they read this, because it's epidemiologic, and uncontrolled confounding might explain some of the relationships. But the message is still pretty positive: not to smoke, be physically active as much as one can be, and take a drink occasionally."

"These types of studies are very valuable," James F. McDonnell, MD, professor of ophthalmology at Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, told Medscape Medical News. Although they have value in showing trends, there are limitations because of the decisions researchers have to make in terms of what variables to consider, he said.

Questions Remain

For instance, "in this study, we don't know why they're sedentary. Are they sedentary because they're demented or have some other kind of medical illness? Some are sedentary not because they choose to be sedentary," Dr. McDonnell explained.

He added, however, "We do know that alcohol and cigarettes are very oxidative. They both cause a lot of oxidation, and that's one of the problems with retinas and aging in general."

"The most important thing is that the 20-year cumulative incidence of visual impairment was 5.4% and that there was a mean loss of 1.6 letters between examinations, and a cumulative 20-year loss of 6.6 letters, and that being a current or past smoker was related to a greater change in those numbers. That tells us from a population base what you can expect people to lose," Dr. McDonnell concluded.

This study was supported by the National Institutes of Health and Research to Prevent Blindness. The authors and Dr. McDonnell have disclosed no relevant financial relationships.

Ophthalmology. Published online March 3, 2014. Full text

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