Haven't read the study yet, though I've been associated with research at the same department. Usually the study design is using matched controls which negates t

Haven't read the study yet, though I've been associated with research at the same department. Usually the study design is using matched controls which negates the effect of the parameters you mention. Sweden basically has free healthcare so there is not much difference in access to care, and controlling for the potential residual factors makes studies results quite stable.