Age-, gender-, and socioeconomic status-specific incidence of Parkinson's disease and parkinsonism in northeast Scotland: the PINE study.

There have been few high quality incidence studies of Parkinson's disease (PD). We measured age-, gender- and socioeconomic-specific incidence rates for parkinsonism and PD in north-east Scotland, and compared our results with those of previous high quality studies. Incident patients were identified prospectively over three years by several overlapping methods from primary care practices (total population 311,357). Parkinsonism was diagnosed if patients had two or more cardinal motor signs. Drug-induced parkinsonism was excluded. Patients had yearly follow-up to improve diagnostic accuracy. Incidence rates using clinical diagnosis at latest follow-up were calculated for all parkinsonism and for PD by age, gender and socioeconomic status. Meta-analysis with similar studies was performed. Of 377 patients identified at baseline with possible or probable parkinsonism, 363 were confirmed as incident patients after median follow-up of 26 months (mean age 74.8 years, SD 9.8; 61% men). The crude annual incidence of parkinsonism was 28.7 per 100,000 (95% confidence interval (CI) 25.7-31.8) and PD 17.9 per 100,000 (95% CI 15.5-20.4). PD was more common in men (age-adjusted male to female ratio 1.87:1, 95% CI 1.55-2.23) but there was no difference by socioeconomic status. Meta-analysis of 12 studies showed an incidence of PD (adjusted to the 1990 Scottish population) of 14.6 per 100,000 (95% CI 12.2-17.3) with considerable heterogeneity (I(2) 95%), partially explained by population size and recruitment duration. The incidence of PD was similar to other high quality studies. The incidence of PD was not affected by socioeconomic status.