NEW YORK - Older men and women with cataracts or age-related macular degeneration (ARMD) are at increased risk for suffering an early death, relative to older people without these two types of visual impairment, a study hints.

But it's not clear, the study team notes, whether the vision loss is simply a marker for deterioration due to aging or if, in and of itself, the conditions boost mortality risk.

While a number of studies have found visual impairment boosts mortality risk among older people, research on the relationship between cataracts or ARMD and mortality has yielded mixed results, Sudha Cugati of the University of Sydney and colleagues note in the Archives of Ophthalmology.

Cataracts occur when the clear lens over the eye clouds up, while ARMD is a progressive deterioration of the back of the retina.

To better understand how ARMD and cataracts might relate to mortality, Cugati and colleagues looked at 3,654 people 49 and older who were participating in a long-term study of eye health.

Fifty-four percent of people with any type of visual impairment died during the study's 11-year follow-up period, the researchers found, compared with 34 percent of those with no vision problems.

Mortality during follow-up was 45.8 percent for those with ARMD, versus 33.7 percent for those without the condition. And 39.2 percent of people with cataract died during the study's follow-up period, compared to 29.5 percent of those with no cataracts.

Once the researchers used statistical techniques to adjust for other factors linked to mortality risk, the increased risk of death with cataracts remained significant, while the increased risk of mortality with ARMD was significant only for people younger than 75.

"This is an important finding given that a major proportion of visual impairment is due to treatable causes," Cugati and colleagues write. There are a number of ways in which vision loss could increase mortality risk, they add, for example by causing disability, depression and loss of independence.

People who had had cataract surgery previously were not at increased risk of dying during the study follow-up, the researchers note. "This could be partly explained by the likely healthier lifestyle and health awareness among persons undergoing cataract surgery and could provide evidence to support benefits from interventions to correct visual impairments in older persons," they write.

If future research finds that vision loss does indeed lead to an earlier death, they add, "regular assessment of vision in older persons may lead to early detection, facilitating treatments that could reduce the impact of visual impairment."