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Cataracts Increase Mortality Among Older Non-Diabetic Women

Older women with cataracts have a significantly higher risk of death than men, among non-diabetics.

This finding could be due to one or more "sex specific" factors, postulates Dr Darwin Minassian and colleagues at the Institute of Ophthalmology, University College London. Researchers.

Researchers note that the 1985 Framingham Eye Study in the United States found increased mortality in cataract in diabetics, but no such effect was found in the non-diabetic cohort. A second US study in 1995 found that poor survival in non-diabetics was associated with level of severity of nuclear sclerosis (one of three main types of cataract), but no such association was found in diabetics.

A random sample was studied of 1,500 people -- around 900 women and 600 men -- with cataracts who were aged 65 and older. The cohort was drawn from 17 London family practices monitored over four years. The age and sex specific mortality from various causes was estimated and compared in those with and without cataract.

At the end of four years, 222 men and women had died, including 31 diabetics. The researchers analysed diabetics and non-diabetics separately, because of the risk factors associated with diabetes.

In the non-diabetic group (1,318 subjects) , the researchers found among 814 women, having a cataract increased the death rate from 25 per 1,000 to 40 per 1,000. There were no such differences among the men, in whom death rates were similar in those with cataracts. 58 per 1,000, and without cataracts, 63 per 1,000.

In the diabetic group, the death rate was significantly higher among both men and women with cataracts. There were no differences to the findings when the researchers accounted for race, smoking, area of residence, and type of cataract.

Dr Minassian thinks a possible explanation for the differential risk in women "is that there may be one or more 'sex specific'" risk factors (for cataract and mortality), to which men have little or no exposure. Possible risk factors that warrant further investigation may be those associated with some pregnancy and childbearing experience. Another possible explanation for our findings is that men have higher exposure to factors that increase mortality but not the risk of cataract."

Repeated finding of higher cataract prevalence in women compared to age matched men is consistent with this idea. Detailed lifetime exposure data on factors that might cause systemic damage resulting in both higher risk of cataract and higher mortality could offer valuable pointers to risk factors for cataract, they conclude.
British Journal of Ophthalmology 2002; 86:424-8.

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