This study looks at the current and projected prevalence of Parkinson's in the USA. Although the sources of data vary substantially, the authors do a good job of combining estimates and provide clear discussion for why estimates from some sources may lack precision. This kind of work is essential for planning health care resources, now and in the future. It also puts into sharp focus the increasing burden of disease and what neuroprotective therapies would mean in the fight against the rising tide....
Alastair Noyce
NPJ Parkinsons Dis. 2018 Jul 10;4:21. doi: 10.1038/s41531-018-0058-0. eCollection 2018.
Marras C, Beck JC, Bower JH, Roberts E, Ritz B, Ross GW, Abbott RD, Savica R, Van Den Eeden SK, Willis AW, Tanner CM; Parkinson’s Foundation P4 Group.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039505/
Estimates of the prevalence of Parkinson's disease in North America have varied widely and many estimates are based on small numbers of cases and from small regional subpopulations. We sought to estimate the prevalence of Parkinson's disease in North America by combining data from a multi-study sampling strategy in diverse geographic regions and/or data sources. Five separate cohort studies in California (2), Minnesota (1), Hawaii USA (1), and Ontario, Canada (1) estimated the prevalence of PD from health-care records (3), active ascertainment through facilities, large group, and neurology practices (1), and longitudinal follow-up of a population cohort (1). US Medicare program data provided complementary estimates for the corresponding regions. Using our age- and sex-specific meta-estimates from California, Minnesota, and Ontario and the US population structure from 2010, we estimate the overall prevalence of PD among those aged ≥45 years to be 572 per 100,000 (95% confidence interval 537-614) that there were 680,000 individuals in the US aged ≥45 years with PD in 2010 and that that number will rise to approximately 930,000 in 2020 and 1,238,000 in 2030 based on the US Census Bureau population projections. Regional variations in prevalence were also observed in both the project results and the Medicare-based calculations with which they were compared. The estimates generated by the Hawaiian study were lower across age categories. These estimates can guide health-care planning but should be considered minimum estimates. Some heterogeneity exists that remains to be understood.
Any estimate of numbers of cases of Parkinson's Disease are low, as the current diagnostic criteria eliminate people in the earliest stage of the disease - particularly for women - when there is often a cluster of non-motor symptoms but no or very mild sporadic motor symptoms. Much of the research shows that women and people with LRRK2 familial PD present with mild symptoms and slower progression, and yet the diagnostic criteria preclude such patients until motor symptoms develop, at which point the damage to neurons has progressed to as much as 60% loss. While an earlier diagnosis may not prevent progression of the disease at this point, it would offer more accurate estimates of numbers of patients, and would offer a better psychosocial outcome for these patients and their families. Without a diagnosis, even a preliminary diagnosis that could be changed later if it is found to not fit, is better than no diagnosis. People with the subtle symptoms - the vast majority are women - are thought of as exaggerating, imagining, psychosomatic, hypochondriacs. Loss of smell, tripping, dropping things, genetic predisposition, postural deficit, chronic neck pain and stiffness, muscle cramps - all of this isn't enough for a diagnosis because there isn't a clear-cut motor symptom such as a tremor or the inability to draw the face of a clock. AND YET those are advanced symptoms that would indicate significant neuron damage. SO WHY NOT BELIEVE IN THE SUBTLE SYMPTOMS THAT COME FIRST? No, there's no cure, but why put someone through the doubt, uncertainty, lack of community and lack of support that goes with no diagnosis. It's just a clinical diagnosis anyway, so why not give it a little sooner? Women shouldn't have to wait 7-10 years when they know something is wrong and nothing else fits but the medical community won't acknowledge the subtleties, even when accompanied by plenty of circumstantial evidence. Let's change the diagnosis criteria to include Stage 0 - pre-symptomatic PD - when everything points in that direction. THEN you will have a more accurate estimate of numbers of cases.
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