This is not a new question. And it is the sort of question that would interest many patients on ADT, who feel like their joints are aching more now than in the past.
A year ago, in a paper in the Annals of Oncology, it was reported that “ADT was associated with an elevated risk of being diagnosed with [rheumatoid arthritis]”. That conclusion was drawn from a retrospective study of data on over 100,000 men, of which almost 45,000 had received ADT as part of their prostate cancer treatments.
Now we have a new paper, published in Prostate Cancer and Prostatic Disease, which arrives at the opposite conclusion. The new study was based on data collected on 5590 prostate cancer patients in Taiwan, who have been treated with ADT, compared to an equal number off age-matched Taiwanese patients, who had not been treated with ADT. The new study looked at not just the incidence of rheumatoid arthritis, but over 30 other autoimmune diseases. The authors of the new study conclude that "ADT use in patients with [prostate cancer] was associated with a decreased risk of autoimmune diseases."
So how do we explain these discrepancies? For one thing, the new study had a smaller sample size and surveyed many more autoimmune diseases. There were relatively few patients with rheumatoid arthritis: 24 ADT patients and 46 in the control group. The authors acknowledge that in their sample size was small and the decrease in the risk of arthritis they observed was not considered statistically significant.
But they also recognized that there is considerable difference in the risk of rheumatoid arthritis between different populations. Even without prostate cancer (or ADT), the risk of rheumatoid arthritis is higher in North American populations—be they Native American or descendants of more recent immigrants—than in Asian populations.
About the strongest conclusion we can reach is that we do not know whether ADT increases or decreases the risk of rheumatoid arthritis, but racial differences may outweigh any impact that ADT might have on that particular autoimmune disease.
The abstract for both papers can be found at:
https://academic.oup.com/annonc/article/29/2/386/4756049
and
https://www.ncbi.nlm.nih.gov/pubmed/30692587
Androgen deprivation therapy for prostate cancer and the risk of autoimmune diseases. In: Prostate Cancer Prostatic Dis. 2019 Jan 28
Androgen deprivation therapy and risk of rheumatoid arthritis in patients with localized prostate cancer. In: Ann Oncol. 2018 Feb 1;29(2):386-391