To analyse the incidence and prognosis of Parkinson disease in the general population and to evaluate whether subjective motor complaints might be predictive of future disease.
Prospective cohort study.
6969 participants aged 55 years or older underwent interviewing, physical examination, and cognitive testing in three examination rounds in the period 1990-1999. In addition there was continuous automated datacollection. We calculated age- and sex-specific incidence rates, the relative risk of dementia and mortality, and the relationship between subjective motor complaints at baseline and the future risk of Parkinson disease.
During the follow-up period, 67 participants were diagnosed with Parkinson disease based on clinical criteria. 39% of those had not received this diagnosis before. Incidence rates per 1000 person-years for each age-category were 1.4 (65-74 years), 3.3 (75-84 years) and 4.3 (85 years and older), respectively. Patients with Parkinson disease became demented more often (HR 2.80, 95%CI 1.79-4.38) and had a shorter life expectancy (mortality HR 1.83, 95%CI 1.47-2.26) than participants without the disease. Subjective complaints of stiffness, tremors, and imbalance without clinically obvious parkinsonian signs were associated with a significantly increased risk of a future diagnosis of Parkinson disease.
Parkinson disease in the general population is probably not always recognized and is associated with and increased risk of dementia and reduced survival. Dopamine shortage early in the course of the disease might result in subtle complaints long before the typical motor symptoms develop.