The risk of cataracts more than doubles if patients with systemic lupus erythematosus have been on 10 mg/day of prednisone, or its equivalent, for 3 or more years, according to a retrospective review of 2,109 patients at Johns Hopkins University in Baltimore.
After the researchers controlled for age, sex, and other potential confounders, they found that the risk triples when patients have been on that dose for 10 or more years (relative risk, 3.1; 95% confidence interval, 1.6-5.7; P = .0005). The doubling of risk was found in those who had been on 10 mg/day, or its equivalent, for 3-10 years (RR, 2.3; 95% CI, 1.3-4.3; P = .0065). Shorter courses did not increase the risk of cataracts (Rheumatol. Int. 2014 Sept. 26 [doi:10.1007/s00296-014-3129-5]).
It’s not news that long-term prednisone causes cataracts, but the findings give an idea of how long it takes – and how much drug is needed – for problems to emerge. Overall, in patients with systemic lupus erythematosus (SLE), “the cumulative prednisone dose was the most important risk factor for cataract[s],” concluded Dr. Khaled Alderaan, a postdoctoral fellow in rheumatology at Johns Hopkins University, and his team. Also, the risk of cataracts doubled if patients had a mean systolic blood pressure above 140 mm Hg over a median of 4.1 years of follow-up (RR, 2.2; 95% CI, 1.4-3.3; P = .0006 ), and the risk increased 30% for every 2-point increase in disease activity, as measured on the SELENA–SLEDAI (Systemic Lupus Erythematosus Disease Activity Index, as modified for the Safety of Estrogens in Lupus Erythematosus National Assessment) (RR, 1.3; 95% CI, 1.1-1.5; P = .0005).
“These results provide further incentive for controlling blood pressure and disease activity in SLE,” the authors concluded.
The patients, all members of the Hopkins Lupus Cohort, were seen quarterly by their rheumatologists and examined every half year by their ophthalmologists. About half were under 40 years old when they enrolled, and the rest were under 60 years old. Most of the patients (93%) were women, and most were either white (54%) or black (39%). They had no cataract history when they joined the cohort.
Cataracts were not associated with lupus duration, diabetes, smoking, high cholesterol, renal involvement, immunological profile, and medication history other than prednisone. Diabetes, smoking, and high cholesterol are all known to increase the risk of cataracts in the general population.
During a total of 11,887 persons-years, the cohort had a cataract incidence of 13.2/1,000 persons-years.
“High disease activity would be an indication for higher corticosteroid doses. However, in our multivariate analysis, the association of disease activity with cataract persisted after we controlled for corticosteroid doses. Another potential explanation of the association between disease activity and cataract is an immunological impact of SLE on ocular cytokines and growth factors. Imbalance between these cytokines can facilitate the formation of cataract, as proposed in the general population,” the investigators noted.
“In the general population, the relationship between hypertension and cataract has been inconsistent. Moreover, the pathophysiological mechanism of hypertension-induced cataract remains uncertain. Some have debated the potential association may be affected by confounding factors such as diabetes or smoking. In our study, the association persisted after controlling for all other confounding factors,” they wrote.
Men in the study had a 20 % lower risk of cataracts than did women. “Although this finding was not statistically significant, it is consistent with general population studies.” The reasons for the sex differences are unknown, the researchers wrote.
The work was funded by the National Institutes of Health. The investigators have no competing financial interests.