Later age at onset in Parkinson's disease over twenty years in an Italian tertiary clinic

Background: Age is considered an important risk factor for Parkinson's disease (PD). However, although life-expectancy has increased considerably, incidence rates of PD appeared to be stable over the last two decades. Accordingly, an increase in mean age at onset over time could be expected. We investigated the changes in age at onset in PD over the last two decades. Methods: All consecutive PD patients assessed over a 18-year period (1995-2013) in a single tertiary outpatient clinic were included in the present retrospective cohort study. Results: After adjusting for several confounders (gender, positive family history for PD, education, smoking at onset and past exposure to environmental/occupational pollutants), 5-year cohorts of year of disease onset were associated with increasing age at onset in both prevalent (N = 6996) and incident (N = 4172) cases (for trend, P <0.001). From 1995-2000 to 2010-2013 there was an increase in predicted age of 4.1 years (95% CI, 3.0-5.2) and 3.9 years (95% CI, 2.7-5.1) in prevalent and incident cases, respectively. However, the change in predicted age at PD onset, across cohorts of year at onset, showed a steeper increase than the corresponding sex and cohort-matched mean age from the official Italian statistics. Conclusions: Over the last two decades, age at onset of PD appeared to shift progressively towards more advanced age. However, sequential, high-quality population-based incidence studies are required. To establish whether there is a trend towards increase in age at onset over and above general population ageing and to assess whether the increase is associated with improved medical and socio-economic conditions.