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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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