The researchers said they did the study with the aim of finding more information about the interaction between age and Parkinson disease (PD) in an effort to improve patient management and therapy development.
Older age at disease onset in Parkinson disease (PD) is mostly linked with more severe disease and worse health-related quality of life (HRQOL), although there were exceptions for measures of dyskinesia and dystonia, according to a recent population-based study from Sweden.
Although PD is usually considered a disease of aging, the actual development and appearance of PD can vary widely, and researchers now generally believe that these time factors—not only age of onset but disease duration—may influence the overall course of disease and the type of motor and nonmotor symptoms that may appear.
The researchers said they did the study with the aim of finding more information about the interaction between age and PD in an effort to improve patient management and therapy development.
With that in mind, the researchers sought to analyze the change in different aspects of PD over time, including symptom scores, HRQOL, clinical scale components, and medication use by aging and disease duration.
The study, published in Scientific Reports, used data from the Swedish National Registry for Parkinson’s Disease, called PARKreg, which began in 2011; it includes demographic variables, diagnosis, treatments, physician-reported clinical measures of disease severity, and patient-reported outcomes.
The current study is based on data for 1436 patients with idiopathic PD from the southernmost region of Sweden, Scania; data retrieval occurred in April 2020. Patients were followed longitudinally for up to about 7.5 years from enrollment (3470 visits covering 2285 patient-years; average follow-up time 1.7 years).
The median age at baseline was 72 years, the median time since PD diagnosis was 4.2 years, and the median duration of motor symptoms was 6.2 years. Ninety percent of the patients were on levodopa at the time of their baseline visit, and most patients had mild disease and were classified as stage I or II according to the Modified Hoehn & Yahr scale.
Researchers also used the Clinical Impression of Severity Index for Parkinson's Disease, a 6-item scale, and the Non-Motor Symptom Questionnaire (NMSQ), a 30-item scale. Dystonia and daily dystonia time were evaluated along with freezing of gait and off fluctuations. Medicine usage was taken from another linked national database in Sweden. Using a variety of statistical analyses, the researchers examined the data for interactions between age at onset and different outcomes.
For the most part, being receiving a diagnosis at an older age correlated with a faster worsening of motor symptoms.
This did not apply to dyskinesia and other levodopa-associated motor fluctuations, which tended to be worse when patients received their diagnosis at a younger age. OFF periods were more frequent as the disease progressed, but no interaction was seen with age.
For older patients, HRQOL worsened over time, as did certain nonmotor symptoms, including unexplained weight change, hallucinations, and double vision.
For the NMSQ total score, the investigators saw an interaction with time and age in that later onset was linked with slightly more nonmotor symotoms and more symptoms emerging over time.
The study had several strengths, including its size, the population-based cohort, the longitudinal study design, and the ability to link patients to the Swedish Prescribed Drug Register to capture medication use.
One notable limitation is that it did not include Unified Parkinson's Disease Rating Scale. In addition, the NMSQ only captured the presence of symptoms and not changes in severity or frequency. Lastly, the study did not include any analysis about the effect of comorbidities.
Raket LL, Oudin Åström D., Norlin, JM, Kellerborg Km Martinez-Martin P, Odin P. Impact of age at onset on symptom profiles, treatment characteristics and health-related quality of life in Parkinson’s disease. Sci Rep. Published online January 11, 2022. doi:10.1038/s41598-021-04356-8