You stay physically active, but you are also fond of the occasional drink? Not to worry, you may be doing your eyes a favor, according to new research in the journal Ophthalmology.
"Visual impairment" - loss of sight caused by eye disease, trauma or a congenital or degenerative condition that cannot be corrected by glasses - is on the rise.
Projections estimate that by 2020 there will be at least 4 million people in the US with visual impairment - a 70% increase from 2000.
This is because, while the population is increasingly living to older ages, age-related eye diseases remain common.
Finding ways to decrease the prevalence of visual impairment is therefore becoming more important. This new study examines to what extent certain modifiable lifestyle behaviors - smoking, drinking alcohol and physical exercise - have an impact on visual impairment.
The researchers, from the University of Wisconsin School of Medicine, analyzed data from the Beaver Dam Eye study, a long-term study that followed nearly 5,000 participants aged 43-84 years between 1988 and 2013.
Over a period of 20 years, 5.4% of the people in the study developed visual impairment.
The researchers found that people who exercised three or more times a week were less likely to get visual impairment. About 2% of physically active people became visually impaired, compared with 6.7% of people who led a sedentary lifestyle. When the researchers adjusted their findings for age, they found that physically active people were 58% less likely to develop visual impairment than sedentary people.
Non-drinkers versus occasional drinkers
Non-drinkers were more likely to become visually impaired than occasional drinkers - 11% of non-drinkers developed visual impairment, compared with 4.8% of occasional drinkers.
The study found that non-drinkers were more likely to become visually impaired than occasional drinkers.
Again, adjusting for age, the researchers calculated that occasional drinkers were 49% less likely to become visually impaired than people who abstain from alcohol.
The study classes occasional drinkers as people "who had consumed alcohol in the past year but reported zero servings in an average week." People who had not consumed alcohol in the past year were categorized as non-drinkers.
Although occasional drinking seemed to protect against visual impairment, the researchers did find that heavy drinkers and smokers were slightly more at risk of developing visual impairment, but that the risk increase was not enough to be statistically significant.
For instance, the study records that the risk of visual impairment for people who drank less than one alcoholic beverage a week was about the same as the risk for people who drank one or two alcoholic drinks each day.
How reliable were the results of this study?
The data for this study came from a large, long-term research project, but there may have been factors that influence the accuracy of the study's findings. For instance, the Beaver Dam Eye Study did not record some of the details about how physically active the participants were - such as how long their sessions of physical activity were.
Also, the people in the study who had more sedentary lifestyles were less likely to return for follow-up examinations than the physically active people, so this may have skewed the results slightly.
The study also did not have a large enough sample base of participants with some behaviors - such as heavy drinking - to be sure about how this might affect visual impairment risk.
But the researchers feel confident that their study highlights the protective benefits of physical activity against visual impairment.
"While age is usually one of the most strongly associated factors for many eye diseases that cause visual impairment, it is a factor we cannot change," says Dr. Ronald Klein, lead researcher of the study.
"Lifestyle behaviors like smoking, drinking and physical activity, however, can be altered. So, it's promising, in terms of possible prevention, that these behaviors are associated with developing visual impairment over the long term. However, further research is needed to determine whether modifying these behaviors will in fact lead to a direct reduction in vision loss."