Epidemiology of Parkinson's Disease: A Population-Based Study in Primary Care in Italy

There are no studies on prevalence, incidence and comorbidities of Parkinson's disease (PD) in the Italian population.

The database of 700 Italian general practitioners (population, 923,356) was investigated. All patients with International Classification of Diseases Ninth Revision - Clinical Modification (ICD-9-CM) diagnosis of PD during the period 2002-2012 were included. Parkinsonisms were excluded. Clinical conditions preceding PD were identified through ICD-9-CM codes. The Charlson Comorbidity Index was used. PD crude and standardized prevalence and annual incidence were calculated. Crude and adjusted hazard ratios were calculated for comorbidities.

A total of 2,204 patients (1,140 men, 1,064 women, age 22-95 years) were included. The crude prevalence of PD was 239/100,000. Prevalence increased exponentially with age. Standardized prevalence was 233 (95% CI 232-235). One hundred ninety-four patients were newly diagnosed, giving a crude incidence of 22/100,000 and a standardized incidence of 23.1/100,000 (95% CI 22.9-23.2). Incidence increased steadily until age 75-84 years and then decreased. Older age, cardiovascular and gastrointestinal disorders, diabetes, and restless-legs syndrome were associated with increased PD risk and smoking and hypersomnia with decreased PD risk. The Charlson Comorbidity Index was associated with PD risk with a documented gradient.

Prevalence and incidence of PD in Italy are in line with studies with the highest case ascertainment. PD risk varies with the number and type of comorbidities.