SYDNEY — Progression of Parkinson's disease (PD) can be highly variable, and dementia, psychosis, and dysphagia are not invariable features of the disease, even when disease duration is longer than 30 years, researchers from Italy have observed.

The few studies that have described the long-term clinical course of PD have reported data only up to 20 years of disease duration, and those studies had small samples sizes, until now.

At the Movement Disorder Society (MDS) 17th International Congress of Parkinson's Disease and Movement Disorders, Roberto Cilia, MD, and colleagues at the Parkinson Institute in Milan, Italy, reported data on motor and nonmotor features of PD in a large cohort of patients 20 years – and in some cases 30 years – from diagnosis.

The retrospective cross-sectional study included all consecutive PD outpatients with disease duration beyond 20 years attending their center from 1998 until September 2012. A total of 320 patients had PD for 20 to 22 years, 168 had PD for 23 to 25 years, 89 patients for 26 to 28 years, and 50 had PD for 29 years or longer.

Slow Progression

The researchers report that disease progression "may be extremely variable; it may be slow-progressing" with only 50% of patients in Hoehn & Yahr stage greater than 4 at 30 years after diagnosis.

And although postural instability is an invariable feature of advanced PD (seen in all patients at 30 years), this is not true for falls, probably because of preventive strategies such as use of wheelchairs, they note.

Dementia also does not appear to be an invariable feature of late-stage PD, according to this study. "The prevalence of dementia remains about 30% to 35% over 20 years, including those over 30 years from the PD onset," Dr. Cilia told Medscape Medical News.

Indeed, 65% to 70% of patients in the cohort are dementia-free even after 30 years from onset, the study team says. "Most notably, mortality does not seem to be associated with dementia but rather to aging, dysphagia, postural instability, and orthostatic hypotension," they say. At 30 years, psychosis was present in 32% of patients, dysphagia in 39%, and orthostatic hypotension in 11%.

The data also suggest that pharmacologic therapy reaches a plateau at 30 years, with a levodopa-equivalent daily dose of 750-800 mg/day; antidementia drugs are prescribed in only 10% of patients; and 16% to 25% of patients had an advanced-stage therapy such as deep brain stimulation, continuous apomorphine infusion, or continuous duodenal levodopa infusion.

Dr. Cilia points out that the prevalence of dementia in this Italian cohort (about 30% to 35%) is substantially different from that seen in the Sydney Multicenter Study of Parkinson's Disease, in which 80% of patients had dementia at 20 years ( J Neurol Neurosurg Psychiatry 2011;82:1033-1037).

Longer Disease Duration

Commenting on the findings for Medscape Medical News, Glenda Halliday, PhD, from Neuroscience Research Australia and University of New South Wales, Sydney, who was involved in the Sydney study, said that the research by Dr. Cilia and colleagues "assessing progression of PD beyond 20 years differs from the Sydney longitudinal study in a number of ways that may affect the conclusions."

"They have recruited a population of patients with PD who have an average age of onset under the age of 50, whereas the Sydney study recruited a typical population of patients with an average age of onset of 60. This means that the age assessed after 20 years is significantly older in the Sydney cohort compared to the Italians," she said

"The reason the Italians have a bias towards patients with younger onset is that they targeted people with long-duration PD for their study. It is well documented that the younger the age of onset, the slower the disease progression, so it is not surprising that there is variability in disease progression," Dr. Halliday said.

"Even though the study populations differed significantly, with the Sydney cohort more typical of general neurological practice, the large variability in disease progression in Italians was also seen in the Sydney study, where it was related to the age of disease onset," Dr. Halliday noted.

She also pointed out that the Italian team performed its assessment of features cross-sectionally at an average age of 70 according to group recruitment for longer durations of PD, whereas the Sydney study performed assessments in a sequential manner every 3 to 5 years and could analyze additional change over time.

"Of note," Dr. Halliday said, "the Sydney study saw around the same amount of dementia in patients at an age around 70 or less. A major outcome of the Sydney study was that chronological age was most related to the onset of cognitive impairment and dementia over time. The prediction from the Sydney study is that if the 70-year-old Italian cohort was followed for another 5 years, they would see a significant number of them with significant cognitive impairment and/or frank dementia."

Dr. Cilia said her team is "still working on the statistical analyses to confirm or confute some of the main findings from the preliminary data presented in the poster. Therefore, no definite conclusion can be made from these data until we conclude all the analyses."

The research was supported by the Fondazione Grigioni per il Morbo di Parkinson.

Movement Disorder Society (MDS) 17th International Congress of Parkinson's Disease and Movement Disorders. Abstract 910. Presented June 20, 2013.

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