Allopurinol use and risk of multiple sclerosis.

BACKGROUND

Low uric acid levels have been observed in patients with multiple sclerosis (MS). As allopurinol is commonly used to lower uric acid in gout patients, this study examined allopurinol use in individuals with MS during the five years before diagnosis, compared to a matched control group.

METHODS

This nationwide case-control study used Danish health registry data. 9,063 individuals diagnosed with MS between 2008 and 2023 were included on the day of MS diagnosis, while 90,630 controls, were matched from the general population. Controls were matched on age, gender, place of residence, and inclusion date. Allopurinol prescriptions were tracked annually for five years prior to the inclusion date. The primary outcome was the odds ratio of allopurinol use in MS patients compared to controls, analyzed using conditional logistic regression.

RESULTS

In the five years prior to the MS diagnosis or matching date for controls, allopurinol use was consistently lower in MS cases. In total, 0.30% (n = 27) of MS cases had at least one allopurinol prescription, compared to 0.62% (n = 558) of controls, corresponding to an odds ratio of 0.48 (95% CI: 0.33-0.71).

CONCLUSIONS

Individuals diagnosed with MS had significantly lower allopurinol use in the five years preceding their diagnosis, suggesting an inverse relationship between uric acid levels and MS risk. Reduced uric acid levels may be associated with early MS development, possibly due to its antioxidant properties or metabolic changes. Alternatively, these findings suggest a possible protective effect of allopurinol against MS, warranting further investigation.