I am not convinced. they are using a person's ability to get a cold (by having it basically sprayed in their face) as their operational definition of health.

I am not convinced. they are using a person's ability to get a cold (by having it basically sprayed in their face) as their operational definition of health. to me this is extremely flawed. not only does past exposure play a huge role, so does DNA, let alone other behavioral habits that may separate the groups beyond just 'the system is against them'. i dont know anything about who was selected in the Pittsburgh study, but being from that area I know there is huge opportunity for ethnic selection bias even within the 'white' group.