Data Issues in Autoimmune
Data for autoimmune diseases are substantially lacking and inconsistent. The US gathers no statistics on autoimmune diseases as a group, nor even national data on marquee diseases. Therefore, total autoimmune incidence & prevalence figures are, at best, estimates. Unlike cancer, there is no national strategic research plan for autoimmune research, no national effort to collect data on AIIDs, and no long-term, population-based epidemiological studies. This both stems from and contributes to a lack of awareness of autoimmune diseases and how prevalent they are.
The existing data are only by individual diseases, sourced variously from claims, actuarial data, and patient registries. These are reasonable estimates for the more common marquee “big-name” AIIDs but wildly inaccurate for rare diseases. Only the top 20 or so autoimmune diseases have acceptable data. There is no grouping of disease data into larger clusters, and most attempts at this prove inaccurate (we’ve tried!).
The lack of data creates poor awareness and evidence, preventing adequate research funding to remedy this issue. Recently, the NIH has drawn attention to data issues in autoimmune in their report, “Enhancing Autoimmune Research” which will be discussed in the next blog post.
Marquee Diseases by Specialty
Click the arrows next to the slide to view the sources.
The marquee autoimmune diseases are generally higher prevalence, with exceptions. Not only are the statistics terrible (no national data collection), but numbers vary depending on how diseases are grouped. E.g., the axial spondyloarthritides include several inflammatory spinal conditions, of which ankylosing spondylitis is the most prevalent. In total, this category equals the size of RA, but RA has much greater awareness and recognition. This contributes to slower diagnosis of AS and SA.
Systemic lupus erythematosus (SLE), is treated by rheumatologists, although joint symptoms are only a small part of the systemic lupus constellation (skin, kidneys, etc.). Rheumatologists also treat psoriatic arthritis because of joint involvement, although many PsA patients had psoriasis before developing joint symptoms. Sjogren’s disease, where the autoimmune attack is on salivary glands and related tissues, affects a population as large as RA but is less well-known.
Neurologists treat a variety of less common autoimmune diseases that attack nerves or brain tissue, of which multiple sclerosis (MS) is the most familiar (female predominant), and Myasthenia Gravis (MG) is a rarer & less familiar disease that predominantly affects males.
GI autoimmune diseases affect at least as many people as RA, with celiac (triggered by gluten sensitivity) the most familiar and prevalent. Many patients with non-GI autoimmune diagnoses have comorbid GI symptoms, likely from the same mechanism that triggers their primary Dx.
More Invisible Autoimmune Statistics
Type 1 diabetes has, since the 1990s, been universally recognized as an autoimmune disease (although triggers have not been identified). There is an increasing consensus that at least some Type 2 diabetes (T2D) is autoimmune, but how much or what the mechanisms are remains unclear. Autoimmune thyroiditis (several individual diseases), like axial spondyloarthritis, has a much higher prevalence than most people realize. Autoimmune is the largest cause of thyroid dysfunction.
Skin diseases are also very prevalent, with autoimmune psoriasis the best recognized. But more people suffer from alopecia areata (causes hair loss) than T1D.
There are dozens of rare (each affects fewer than 200K people) autoimmune diseases. This is a tiny sample of the better-known rare autoimmune diseases. Antiphospholipid Syndrome (APS) is a major cause of miscarriages, MG is a nerve disease that differentially affects males (unlike most AIIDs), Guillain-Barre is a demyelination disease with rapid onset following viral or bacterial infections; the rapid onset alerts patients & providers to the infection trigger. Compare MS, where many cases are likely triggered by EBV infection, but the months or years of latency make it harder to connect. Autoimmune myositis is progressive muscle destruction.
Growing Prevalence of Four Autoimmune Diseases
Prevalence measures the number of patients living with a particular diagnosis (per 100,000) and it is cumulative within a population. As usual, most prevalence statistics are by individual autoimmune diseases, and rolling up totals is tough due to differing methods and assumptions. The slide shows four diseases where the data points show an increase in the last 50+ years.
Some of the growth is likely caused by better diagnosis, e.g., SLE was once a very rare diagnosis but is increasingly detected (it was not zero in 1970!). This is also true for AS, where the length of time to diagnosis has shortened but is still longer than for RA. Similarly, we expect the diagnosis of IBD (Crohn’s & Ulcerative Colitis) has improved in the last 50 years. More people recognize MS, especially milder forms of the disease, today than in 1970 when one of us met an MS patient for the first time.
Increasing prevalence includes later mortality after diagnosis, that is, patients are living longer than they would have in past decades. Despite these confounders, it’s generally agreed that these diseases have increased in real prevalence and are expected to keep growing.
Historical Rheumatoid Arthritis Incidence
Incidence measures new cases, so is a better measure of new diagnoses.
Unlike AS, SLE, MS & IBD, this chart shows declining RA incidence since the middle of the 20th C. As the slope suggests, the incidence (and prevalence) of RA was even higher in the first half of the 20th C (and the 19thC, although data are sparse). Several population factors may explain this:
- In the pre-antibiotic era, strep infections (strep throat, scarlet fever) often progressed to rheumatic fever and triggered RA (& heart disease).
- The early decades in this chart coincide with a massive reduction in smoking in the US; smoking is a well-known risk factor for RA.
- Since 1985, the incidence has been rising slightly. Improved detection and diagnosis may be part of this or undetected environmental factors.
Type 1 Diabetes Incidence 1920-2000
The best historical data on Type 1 diabetes, now universally acknowledged to be an autoimmune condition, comes from Scandinavia, but the general pattern of growth has been similar in the US. Early in the 20thC., T1D was extremely rare (and extremely fatal).
The development of insulin replacement therapy coincided with a dramatic rise in cases of childhood diabetes.
What IS the Total US Prevalence of Autoimmune?
In the absence of good national data, we fall back on several sources. The most-cited number, even today, is from a 1997 NIH/NIAID study that counted only 24 diseases then recognized as autoimmune (the increase in named diseases since shows how recent our understanding of AIIDs is). AARDA (now AA) figures were the first attempt to update the analysis; by 2011, the prevalence number had doubled.
We’ve done our own analysis by totting up the top ten diseases, which easily exceeds the ‘97 figure and rapidly approaches AA’s.
Our conclusion is that AIIDs affect at least 50M Americans, but the error bar remains huge.
Read our other 2023 State of Autoimmunity posts below!
- The Chronic Disease Epidemic: Visible vs. Invisible
- Siloed Treatments & Specialties for Autoimmune Diseases
- The NIH Report: “Enhancing NIH Research on Autoimmune Disease”
Authors: DrBonnie360, Ellen M Martin, & Ellie Duvall
We approach these thought leadership posts from our multi-lens perspectives.
- DrBonnie360: Digital health consultant, clinical dentist, Wall Street analyst, patient & advocate.
- Ellen M Martin: Consultant, editor, life science finance/IR/marcomm, autoimmune caretaker.
- Ellie Duvall: Digital health equity research intern, recent B.S. in Physiological Sciences from UCLA.
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We provide professional consulting services to investment, emerging, and established companies. Our work bridges silos and fills gaps to help our clients improve care for AIID patients and reduce costs. Informed by patient and caretaker perspectives, we urge investors & clients to integrate the best of digital, conventional, and lifestyle medicine into AIID care delivery.
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