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AREDS reinforces earlier cataract risk-factor findings
To date, cigarette smoking appears to be one of the relatively few known modifiable factors associated with cataract.
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ROCKVILLE, Md. – Gender, educational status, sunlight exposure and smoking are risk factors consistently associated with age-related nuclear and cortical cataract, according to several studies, including the Age-Related Eye Disease Study (AREDS) sponsored by the by the National Eye Institute.
Smoking appears to be one of the relatively few known modifiable factors associated with cataract, according to the AREDS Research Group, which reported its findings in a recent issue of Ophthalmology.
This case-control study aimed to investigate possible risk factors for age-related nuclear and cortical cataracts in AREDS participants. AREDS comprises 4,757 patients. The case-control study focused on 4,477 participants between the ages of 60 and 80.
Additional findings in this group of participants included that persons with moderate nuclear opacities were more likely to be female, nonwhite, smokers and to have large drusen. The study also found that moderate nuclear opacities were less common in persons with higher educational status and a history of diabetes, and among those taking nonsteroidal anti-inflammatory drugs (NSAIDs).
Moderate cortical opacities were associated with dark iris color, large drusen and weight change. Higher levels of sunlight exposure and use of thyroid hormones were associated with a borderline level of significance. Moderate cortical opacities were less common in persons with higher educational status.
Methods and outcomes
Slit-lamp photographs were used to classify participants into one of three nuclear categories: moderate nuclear, mild nuclear and control. Retroillumination lens photographs were used to classify participants into one of three cortical opacity groups: moderate cortical, mild cortical and control.
For nuclear opacity, the number of participants classified with moderate or mild opacity or as controls was 615, 2,044 and 1,818, respectively. For cortical opacity, the number of participants classified with moderate or mild opacity or as controls is 1,068, 2,601 and 808, respectively.
With respect to associated risk factors, the AREDS Study Research Group found that, “as expected, the odds ratio for age was large.” The study group reported that the age effect was more marked for nuclear than cortical cataract. For example, the report stated for moderate nuclear cataract the odds ratio (OR) for persons older than 70 compared with persons younger than 66 was 12.7; the corresponding OR for moderate cortical cataract was 5.96.
With regard to gender and race, the risk factor study found the increased risk of cataract for women was only for nuclear cataract, and that while there is a higher risk of nuclear cataracts in nonwhites — who in AREDS are mostly African Americans — no association was noted between race and moderate cortical opacities.
According to the AREDS study group, the association between educational achievement and cataract has been one of the most consistently reported observations in epidemiologic studies of cataract.
“In our study, as in other studies, the relationship persists even after adjustment for potential confounders, such as smoking, alcohol use and diabetes, which have been associated with both educational level and lens opacity severity,” the authors wrote.
The research group reported that while there is a growing consensus that smoking increases the risk of nuclear cataract, no association has been reported for cortical cataract.
“In AREDS, the ORs for nuclear cataract associated with current smoking were 1.96 and 1.44 for moderate and mild nuclear opacities respectively,” they wrote.
“No association was noted for cortical cataracts. Associations between cigarette smoking and nuclear cataract have been reported in case-control, cross-sectional and prospective studies of lens opacities, as well as in studies of incident cataracts and extracted cataracts. The consistency of this finding across studies and in diverse populations, combined with reports of dose-response relationship, suggests that smoking is one of the relatively few known modifiable factors associated with cataract.”
Regarding sunlight exposure, the AREDS Research Study Group found a higher risk of cortical cataract in persons with higher lifetime average annual ocular UV-B exposure, although the finding for moderate cortical cataracts was at a borderline level of significance.
Other risk factors
The relationship between cataract and medications that were being used by at least 5% of the study participants was evaluated. Use of NSAIDs was associated with a decreased risk of nuclear cataract; no associations were noted when aspirin use was examined separately.
Participants who gained 53 or more pounds compared with those who had gained 10 or fewer pounds since age 20 were at increased risk of moderate cortical cataract. Also, users of thyroid hormones appeared to be at a greater risk of cortical cataracts, and there appears to be a statistically significant association between cortical cataract and more advanced forms of drusen, the study found.
Additionally, the increased prevalence of cataract in postmenopausal women, compared with men, has suggested a possible relationship between estrogen and the development of cataract, according to the study group.
For Your Information:
- The AREDS Coordinating Center can be reached at the Emmes Corporation, 401 North Washington St., Suite 700, Rockville, MD 20850-1707; e-mail: aredspub@emmes.com.
Reference:
- AREDS Study Research Group. Risk factors associated with age-related nuclear and cortical cataract: a case-control study in the Age-Related Eye Disease Study: AREDS Report No. 5. Ophthalmology. 2001;108:1400-1408.