Follow my logic. Diseases like arthritis are autoimmune disorders. Yet most people (it’s so well-known, I don’t need a cite) get it in old age–presumably when your immune system is not as good as in your youth. Why?
I actually have some experience with an autoimmune disease. When I was about 17, I was diagnosed with ulcerative colitis. And that makes alot of sense. Even looking back now, I think I was probably at my physical peak at age 17. So what’s the deal with arthritis then?
Is osteoarthritis an autoimmune disease? If not, this might skew your data.
Your question is based on a misapprehension. Just as sam suggests, osteoarthritis (from “wear and tear”) is more likely to occur in older people. But rheumatoid arthritis and other “autoimmune” diseases, like lupus and many others, is more likley to develop in younger people.
Right. Rheumatoid arthritis is an autoimmune disease, osteoarthritis is a degenerative disease. In any case, autoimmune diseases have various age distributions, which do not necessarily correlate to the age where your immune system is the most robust. For example, this is what Wikipedia has to say about the epidemiology of RA: