polyester outgases. you can detect this smell when it is in the dryer if u have a sensitive nose like me. i got this sensitive by repeatedly being exposed to chemicals in workplace. my nose can smell anything. an annoying smell may not give me rls but will give me insomnia.

my best guess is that poly and other synthetics release gases that affect the nerves that produce the rls.

my family doc recommends sleeping in cotton for rls.

personally my rls is position dependent. if i sleep on my back i get it the worst.