In a previous EduFacts, (Volume 3, number 4) some results from the Nurses' Health Study were reported, which indicated an inverse relationship between lutein/zeaxanthin intake and risk of cataract extraction. The authors had presented this data at the 1998 annual meeting of the Society for Epidemiologic Research. The meeting abstract indicated a 22% decrease in risk of cataract extraction with higher intake of lutein/zeaxanthin. The full results were recently published (1) and clarified that the 22% decreased risk was among those in the upper decile (10th percentile) intake level (energy-adjusted) of lutein/zeaxanthin compared with the lower quintile (20th percentile) intake level. Furthermore, there was a significant linear trend (p=0.04) of decreasing risk of cataract extraction with increasing intake level. In a separate publication (2), the same authors have evaluated the relationship between vitamin supplement intake and risk of cataract extraction in the same study cohort.

Methods:

The incidence of cataract extraction was determined during 720,082 person-years of follow-up in a total cohort of 73,956 women nurses aged 45 or older and free of cancer. Over half were followed for 12 years. Vitamin Supplement intake (multivitamins and, A, C and E) was determined at baseline (1980) and every 2 years afterward. Use was categorized as 'never', 'past use', and 4 categories of current use (<2, 2-4, 5-9, and ≥10).

Results:

There were 1377 cataract extractions. Age-adjusted relative risk (RR) associated with <2 years duration of use of vitamin A was elevated and risk of cataract decreased with increasing duration of current vitamin use. However these relative risks were attenuated with control for cigarette smoking.

Among 'never-smokers', duration of use of vitamins C and E of at least 10 years was associated with decreased risk of cataract extraction (relative risks of 0.71 and 0.79 respectively). Risk among 'never-smokers' using vitamin A could not be evaluated due to small numbers.

Despite the decreased risks of cataract extraction demonstrated among non-smokers taking vitamins C and E long-term, the authors concluded that their findings suggested little overall benefit of supplement use. However another interpretation of this study suggests that when eliminating the strong smoking risk factor for cataract, the use of certain supplements may in fact provide additional decreased risk of cataract.

References

1. Chasan-Taber L, Willett WC, Seddon JM, et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in U.S. women. Am J Clin Nutr 1999;70:509-516
2. Chasan-Taber L, Willett WC, Seddon JM et. al. A Prospective Study of Vitamin Supplement Intake and Cataract Extraction among U.S. Women. Epidemiology 1999;10:670-684.