A new study tags the prevalence of autoimmune diseases at 4.6%, or around 15.2 million people in the US. More than 34% have at least one autoimmune disease and 8% have three autoimmune diseases.
Using data from electronic health records, they calculated prevalence figures for dozens of autoimmune disorders. Some of the most notable prevalence estimates are shown below:
- Rheumatoid arthritis, 2.1 million Americans
- Psoriasis, 2.3 million (though this was far lower than the 10.5 million previously published)
- Crohn’s disease, 1.1 million
- Ankylosing spondylitis, 0.3 million
- Multiple sclerosis, 1.4 million
Other interesting findings were of autoimmune disorders that were far less or more prevalent than previously thought:
- Sarcoidosis, 606,000 (or 3-fold higher than previously estimated)
- Celiac disease, 705,000 (or one-quarter of the figure previously published)
- Guillain–Barre syndrome, 75,761 (or 15 times greater than previous estimates)
With the aging of the US population, even if the prevalence of many autoimmune diseases remains relatively stable, the healthcare expenditures associated with them should increase. The reason? More Americans living longer with these chronic diseases, taking medications chronically.
Biosimilars Have Changed the Discussion Around Cost Savings
Biosimilar competition has changed the savings discussion fundamentally. The Association for Accessible Medicines pegged the savings from all biosimilars at $36 billion since their introduction a decade ago, and our own rudimentary calculations found that in their first 18 months of use, the availability of adalimumab biosimilars alone has saved the US health system $11 billion. I won’t belabor that this does not necessarily imply biosimilar utilization. What I offer instead is a different way of looking at biosimilar savings.
Consider this Canadian study using 2017 data: researchers found that prescription drug costs represented 89% of the total direct medical expenditure for patients with inflammatory bowel disease (IBD), compared with 8% for hospital costs and 3% for physician costs. In that study, the prescription drug costs overtook other medical costs beginning in 2002, around the time that adalimumab was launched and infliximab use was growing. As the costs of these IBD medications rose and newer, higher-cost biologics were introduced, the cost gap widened. Hospital-related costs and physician-related costs for IBD remained steady or even decreased a bit in Canada over this timeframe, and perhaps the effectiveness of these biologics was a contributing factor. Of course, the reimbursement methodology of Canada’s health system may have played a greater role.
In the United States, drug costs are higher, but so are other medical costs, meaning that pharmacy-related expenditures are closer to half of the total IBD costs. Looking at it through a different lens, US researchers found that annual per-member per-year costs for patients with IBD in 2016 were approximately $23,000 (vs. $6900 for matched non-IBD controls). Patients treated with biologics had 3.5-fold higher costs in 2016 than patients with IBD not treated with biologics. Differences in disease severity may have contributed to the wide gap in costs.
Since 2016, the price of all branded biologics have increased substantially, so these numbers do not reflect 2025 figures (there are no updated published data to report). Also, biosimilar infliximab became available in 2016 and 2017, but large cost decreases were not seen immediately.
Consider the effect of biosimilar competition: For patients taking adalimumab, biologic drug costs have dropped precipitously. Although you can’t apply an 85% WAC discount to these expenditure figures, you can assume the net costs on adalimumab have dropped by more than half. Applied across all patients taking adalimumab, that dominant pharmaceutical expenditure becomes far less so, and the total cost of care must have fallen significantly as well. One caveat: We have not factored in the rising costs of hospital/physician care into this overview.
Now apply those cost savings across all of the major autoimmune disease categories treated by adalimumab (and now ustekinumab). The cost of treating these diseases become substantially lower, and ensuring the appropriate availability of these medications to more of the patients with these disorders makes a hell of a lot of clinical and fiscal sense.