Estimate of the prevalence of subjects with chronic diseases in a province of Northern Italy: a retrospective study based on administrative databases.

OBJECTIVE: To find a definition of chronic disease based on literature review and to estimate the population-based prevalence rate of chronicity in a province in Northern Italy.

DESIGN: Retrospective observational study based on administrative databases.

DATA SOURCES/SETTING: Archives of the National Health Service that contain demographic and administrative information linked with the archives of ticket exemptions (2000-2019), the hospital discharge and drug prescriptions (2016-2019).

PARTICIPANTS: Subjects who lived in Vercelli Local Health Authority, a Northern Italian province (Piedmont region), and were alive in December 2019.

MAIN OUTCOME MEASURES: Prevalence of subjects with at least one chronic disease identified by administrative sources and stratification of population according to the number of comorbidities. The pathologies considered were: chronic ischaemic heart disease, congestive heart failure, cardiac arrhythmias, hypertension, stroke, neoplasm, asthma, chronic obstructive pulmonary disease, diabetes, thyroid disorders, osteoporosis, rheumatoid arthritis, chronic kidney disease, dementia, autism spectrum disorder, depression, schizophrenia, hepatitis, HIV and substance use disorders.

RESULTS: Our target population was about 164 344 subjects. The overall prevalence of subjects with at least one chronic condition was 21.43% (n=35 212): 19 541 were female and 15 671 were male with a raw prevalence of 22.96% and 19.77%, respectively. The overall prevalence increases with age until 85 years old, then a decrease is observed. Moreover, 16.39% had only one pathology, 4.30% two diseases and 0.74% had a more complex clinical condition (more than three diseases).

CONCLUSIONS: Despite the difficulty of having a unique definition of chronic disease, the prevalence obtained was coherent with the estimates reported by other national surveillance systems such as Passi and Passi d'Argento. Underestimates were observed when international comparisons were done; however, when we used less stringent definitions of chronic diseases, similar results were obtained.