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AS is estimated to affect about one in every 560 people globally.
Estimates on the amount of people with AS vary quite widely by geographical area, with the lowest prevalence in Sub-Saharan Africa, and the highest in Northern Arctic communities. 
Genetically, AS is complex, although it does have a particularly strong association with one gene - HLA-B27. 
Heritability means how much of the differences in a trait (like height) within a group of people can be attributed to differences in genetics.
Something like eye colour has very high heritability (>80%), which means it’s almost completely determined by genetics. Something like a person’s first language has 0% heritability - as that’s entirely to do with their environment.
What it doesn’t mean is how likely something is to be inherited from a parent , as even if a condition had 100% heritability, and so was completely down to genetics, it might be associated with a dominant or recessive gene, or more likely associated with many many genes, which interact in complex ways and which are still being explored & discovered!
Signs of AS usually start to appear between 20 to 30 years of age 
These are the best resources we've found so far on managing and learning about AS . Please let us know if you have other and we'll add them to the list!
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