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Aspirin and cataracts

Study
Results
Comment

Doctor, is it right that taking an aspirin a day prevents cataracts? Interesting question, but is there an informative and authoritative answer? A new long-term analysis [1] suggests that it does not. The trouble is that previous randomised trials of aspirin for heart disease have also looked at cataract, but only over a relatively short time of five or six years. Some [2,3] suggest no effect, while an early analysis from this same trial [4] suggested some protective effect.

Study


The study was a randomised trial of 325 mg daily aspirin plus 50 mg beta-carotene in 22,000 US male doctors aged 40 to 84 years in 1982. In 1988 the aspirin component was stopped because of a significant effect on risk of a first heart attack, but the study continued with beta-carotene, when the average length of follow up was five years.

All cataracts reported up to the end of 1997, with a mean follow up of 15 years form the basis of the study. It is analysed by aspirin use during the randomised aspirin phase (intention-to-treat), and by self-reported aspirin use when doctors were given a free choice about aspirin in the sixth and seventh year of the study. Self-reported cataracts were confirmed, and details and sub types obtained from the treating ophthalmologist, with 92% confirmation.

Results


Over the 15 years the 22,071 doctors, with a mean age of 50 years in 1982, developed 2081 cataracts of which 1198 were extracted. That means that one cataract can be expected for every 10 doctors. There were 1084 cataracts in the aspirin group and 997 in the placebo group. Cataract development increased with duration of follow up, but there were no significant differences between groups (Figure 1).

Figure 1: Cataracts in US male physicians given aspirin or placebo for five years



In the observational analysis according to self-reported aspirin use in the sixth and seventh year, cataract development was significantly higher in doctors using aspirin for more than 180 days a year compared with those who seldom or never used aspirin (relative risk 1.22 (1.04 to 1.43)). Doctors who used aspirin more tended to be older and have more heart disease, but the relationship remained the same even after adjustment for age, therapy and other factors.

Comment


What we can take from this and previous studies showing no association between aspirin and cataract prevention [2,3] is that it is a racing certainty that there is no large or useful effect of aspirin on preventing cataracts. Perhaps the pendulum has swung towards a suspicion that aspirin could even cause cataracts, though that is no more than a preliminary finding. For aficionados, there is a randomised study underway in 40,000 postmenopausal US doctors collecting even more information.

References:

  1. WG Christens et al. Aspirin use and risk of cataract in posttrial follow-up of physicians health study I. Archives of Ophthalmology 2001 119: 405-412.
  2. R Pet et al. Randomized trial of prophylactic daily aspirin in British male doctors. BMJ 1988 296: 313-316.
  3. EY Chew et al. Aspirin effects on the development of cataract in patients with diabetes mellitus: early treatment diabetic retinopathy study report 16. Archives of Ophthalmology 1992 110: 339-342.
  4. WG Christen et al. Low-dose aspirin and risks of cataract and subtypes in a randomised trial of US physicians. Ophthalmol Epidemiol 1998 5: 133-142.
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