Objective: To estimate the national prevalence and incidence of Parkinson’s as a function of age and the implications this has on future disease burden.

Background: New Zealand is an ethnically diverse South Pacific island nation. The resident population at the 2013 census was 4.2 million, with median age of 38 years and life expectancy at birth of 81 years.

Methods: Information on Parkinson’s-related medications was extracted from the national pharmaceutical database of community-dispensed medications for the period 1 January 2005 to 31 December 2014 for all of New Zealand. Drug-tracing methods, calibrated using known diagnoses for a subset of individuals, were used to estimate the number of people with Parkinson’s. Prevalence and incidence rates and cumulative frequency, were calculated by 5-year age ranges up to 100+ using Statistics New Zealand data. Future estimates used Statistics New Zealand population age profile predictions.

Results: Prevalence and incidence by age were stable across the years of available data. Prevalence within each year of data increased exponentially from the 20-24 age group to the 75-79 age group, peaked in the 85-89 age group with 2,200 cases per 100,000, reducing to 2170, 1310, and 640 cases per 100,000 people for the 90-94, 95-99, and 100+ age groups respectively. Similarly, incidence rates peaked at 85-89 years, being 470 per 100,000 person-years, and falling to 340, 260, and 150 per 100,000 person-years for the 90-94, 95-99, and 100+ age groups respectively. One percent of people over 60, 1.5% over 70, 2.1% over 80, 2.0% over 90, and 0.6% over 100 years had Parkinson’s. While the total population in New Zealand is expected to increase by 18% in the next 20 years, the number of people with Parkinson’s is predicted to double in this period, based on the present findings.

Conclusions: The reduction in prevalence and incidence in Parkinson’s after 90 years of age might be explained either by the pool of people susceptible to developing Parkinson’s disease becoming depleted, or under-diagnosis and/or treatment in this age group due to comorbidities. Despite a expected large increase in prevalence of Parkinson’s over the next few decades, the drop in incidence and prevalence post 90 years observed in the present study, rather than a continuous increase with increasing age, will moderate this expectation significantly.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/parkinsons-in-an-aging-population-implications-from-a-nation-wide-prevalence-and-incidence-study-in-new-zealand/