Major international research efforts are being made to fight this trend – including an initiative at London’s Francis Crick Institute, where two world experts, James Lee and Carola Vinuesa, have set up separate research groups to help pinpoint the precise causes of autoimmune disease, as these conditions are known.
“Numbers of autoimmune cases began to increase about 40 years ago in the west,” Lee told the Observer. “However, we are now seeing some emerge in countries that never had such diseases before.
In the UK alone, at least 4 million people have developed such conditions, with some individuals suffering more than one. Internationally, it is now estimated that cases of autoimmune diseases are rising by between 3% and 9% a year. Most scientists believe environmental factors play a key role in this rise.
“Human genetics hasn’t altered over the past few decades,” said Lee, who was previously based at Cambridge University. “So something must be changing in the outside world in a way that is increasing our predisposition to autoimmune disease.”
This idea was backed by Vinuesa, who was previously based at the Australian National University. She pointed to changes in diet that were occurring as more and more countries adopted western-style diets and people bought more fast food.
“Fast-food diets lack certain important ingredients, such as fibre, and evidence suggests this alteration affects a person’s microbiome – the collection of micro-organisms that we have in our gut and which play a key role in controlling various bodily functions,” Vinuesa said.
“These changes in our microbiomes are then triggering autoimmune diseases, of which more than 100 types have now been discovered.”
Hmm. Given that I’m not the P³ I’ll not declare that I’ve got the answer. Instead I’ll just postulate. Human genetics have changed over this time. Or, rather, since the generation or two before that.
In the 1920s a diagnosis of diabetes was a 6 month death sentence. Crohn’s and all the gut ones wouldn’t have increased life of reproductive success chances.
“If you don’t have a certain genetic susceptibility, you won’t necessarily get an autoimmune disease, no matter how many Big Macs you eat,” said Vinuesa.
The susceptibilities are indeed genetically linked and therefore inheritance plays a role. But then so also does the arising, de novo, of the gene combinations that predispose to them.
So, to use another example, 100 years ago – and all time previous to that – babies with lactose intolerance died. So, lactose intolerance was something that only arose de novo in each generation, it wasn’t inherited – or those with it didn’t survive to pass it on, while the gene combinations that cause it might pop up in a sexual mixing of DNA perhaps. Now babies with lactose intolerance do survive and so we have a rise in such intolerance in the population as a whole. We’ve both the directly inherited and also the arising de novo types.
Thus my theory about these autoimmune diseases. They’re increasing because in the past those with them were dead and not reproducing. So, we only got the incidence of those few new cases, not directly inherited, who did survive. Now we’ve got those new cases, as always, plus those directly inherited.
I’d not hold to this very strongly as a complete solution. As with much of economics I’d say that there are likely many things going on. But I would strongly argue that this is some of what’s going on. Some portion – with a heavy emphasis upon “some” – of the rise in autoimmune diseases, as with many others, is a result of the previous generation of those having them not being dead.