In an earlier EduFacts (volume 2, number 5) we reviewed data from 2 case control studies published in 1991, which demonstrated a decreased risk of cataract associated with increased intake of vitamin E - α-tocopherol - through diet or use of supplements. A more recent prospective study (published in 1996) was carried out in Finland, evaluating the effect of plasma vitamin E level on the progression of early cortical lens opacities (1).

Methods:

This prospective study was carried out as a sub-study of a population-based prospective clinical trial evaluating pravastatin in middle-aged men with elevated LDL. Of the 447 study participants, 410 completed ophthalmologic exams at baseline and at 18 months and 36 months after baseline. Plasma α-tocopherol concentration was measured at baseline using high performance liquid chromatographic methods. Lens opacity status was determined using the LOCS II system. Progression of lens opacity was defined as an increase in a particular LOCS grade from baseline to 18 months which was verified at the 36 month visit. 742 eyes were evaluated. Both plasma concentration of vitamin E in цmol/L and lipid-standardized plasma vitamin E concentration were evaluated and related to a progression in LOCS score(s). Statistical adjustments for the correlation between the 2 eyes of a single patient were employed. Plasma linoleic acid, certain carbohydrates, vitamin C, and cholesterol were found to be significantly associated with plasma vitamin E. These variables and pravastatin treatment were included in the statistical models as covariates.

Results:

The mean age in this middle-aged male sample was 57.3 years. Mean baseline plasma vitamin E concentration was 28.09 цmol/L (this is slightly higher than the U.S. population mean - see EduFacts volume 3, number 8). Baseline LOCII score distributions in this relatively young age group indicated that 20.2% of eyes had cortical opacity grades of 1 or more; 7.4% had cortical opacity grades of 2 or more. After 3 years of follow-up, baseline plasma vitamin E concentration and lipid-standardized vitamin E were found to be inversely associated with progression of cortical cataract grade.

Relative Risk of Cortical Cataract Progression (1)
(Lowest vs highest quartile level)

Plasma vitamin E and lipid standardized vitamin E were not associated with progression of nuclear opacity. The authors point out that in this middle-aged population, the majority of lens opacities at baseline were mild. Thus this study was useful in evaluating the effect of vitamin E levels in the early stages of lens opacity formation and progression. They concluded that in this population low plasma vitamin E concentration was a risk factor for progression of early cortical opacity.

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References

1. Rouhiainen P, Rouhiainen H, Salonen JT. Association between low plasma vitamin E concentration and progression of early cortical lens opacities. Am J Epidemiol 1996;144:496-500.