The sources of information, used by the researchers and scientists, working on the matter of comorbidity, were case histories, hospital records of patients and other medical documentation, kept by family doctors, insurance companies and even in the archives of patients in old houses.
Informatsiooni allikatena kasutasid uurijad ja teadlased, kes komorbiidsuse uurimise kallal töötasid, haiguslugude ajalugusid, patsientide haigladokumente ja muid meditsiinilisi dokumente, mida säilitasid perearstid, kindlustusfirmad ja isegi vanades majades elavanud patsientide arhiivides.