Middle-Age Eye Woes Predict Higher Premature Death Rates

SYDNEY, Australia, July 9 -- Cataracts and age-related macular degeneration in middle-age may be warning signs of a higher mortality risk for patients younger than 75, researchers suggested.
Among more than 3,600 patients 49 and older in a long-term longitudinal study, age-related macular degeneration was an independent predictor of death in patients 75 or younger, reported Jie Jin Wang, M.Med., Ph.D., of the University of Sydney and Westmead Hospital, and colleagues.
Any type of cataract was also associated with a higher risk of death, although the effect was not as strong as with macular degeneration D, the authors reported in the July issue of Archives of Ophthalmology.
"The association of visual impairment and mortality has been consistently reported from different populations," they wrote. "Nevertheless, it remains unclear whether the observed association is due to residual confounding factors not completely adjusted for or whether there is a true, direct or indirect, link between visual impairment and mortality."
The investigators looked at the link between visual impairment and death in 3,654 adults who took part in the Blue Mountains Eye Study, a population- based study that enrolled more than 80% of eligible adults in the regions west of Sydney from 1992 to 1994.
The patients were evaluated at baseline for macular degeneration and cataracts using standardized photographic grading. The authors drew on the Australian National Death Index for data on mortality and causes of death among the participants through the end of 2003, and calculated age-standardized mortality rates.
They found that the age-standardized mortality rate was higher among participants with any visual impairment (cataract or macular degeneration), at 54.0% vs 34.0% overall. Among participants with macular degeneration, the rate was 45.8% compared with 33.7% for those without macular degeneration. With cataracts, the age-standardized death rate was 39.2% versus 29.5%.
In Cox regression models controlling for factors that predict mortality --including diabetes, smoking, hypertension and history of myocardial infarction -- neither visual impairment nor macular degeneration were significantly associated with all-cause mortality in all ages. The hazard ratio for visual impairment was 1.3 (95% confidence interval, 0.98-1.7), and for macular degeneration was 1.0; (95% CI, 0.8-1.3)
When the authors looked at participants younger than 75, however, they found that macular degeneration predicted higher all-cause mortality, with a hazard ratio of 1.6 (95% CI, 1.0-2.4).
In addition, any cataract was associated with a hazard ratio for all-cause mortality of 1.3 (95% CI, 1.0-1.5), as were specific subtypes of cataract: cortical (hazard ratio 1.2; 95% CI, 0.97- 1.4), nuclear (hazard ratio 1.2; 95% CI, 0.98-1.5), or posterior subcapsular (hazard ratio, 1.3; 95% CI, 1.0-1.7).
Vascular deaths were significantly more frequent among patients with any visual impairment (P=0.004) and among patients with cataracts (P<0.001), and cancer-related deaths were significantly less frequent in the same two groups (P<0.001). There were no differences in the frequency of respiratory deaths or deaths from other causes between patients with visual impairment or cataract and those without.
There were no significant differences in causes of death between patients with or without macular degeneration, the authors noted.
"After also adjusting for other potential economic and biological confounders, this association became attenuated but remained in the same direction," they wrote. "This is an important finding given that a major proportion of visual impairment is due to treatable causes. In the older group, it could be likely that other age-related conditions dominate the effect on mortality."
They acknowledged that the study was limited by their inability to control for some possible confounders, and by the relatively small number of patients younger than 75 who had macular degeneration.
The study was supported by grants from the Australian National Health and Medical Research Council. Primary source: Archives of OphthalmologySource reference: Cugati S et al. "Visual Impairment, Age-Related Macular Degeneration, Cataract, and Long-term Mortality The Blue Mountains Eye Study." Arch Ophthalmol. 2007;125(7):917-924