It has been suggested that cold reduces flow in the nasal blood vessels and this hinders immune response, giving the virus a foothold for infecting the organism

It has been suggested that cold reduces flow in the nasal blood vessels and this hinders immune response, giving the virus a foothold for infecting the organism. I read a study about a bunch of people being left with their feet in a pool of cold water and it showed an increased infection rate vs the control group, but I don't remember how significant and I cannot find it anymore.